From 022e7c27fe86e5ea151a2404863c6845a8274ba7 Mon Sep 17 00:00:00 2001
From: Andreas Schildbach <andreas@schildbach.de>
Date: Fri, 25 Apr 2014 21:21:11 +0200
Subject: [PATCH] Wrap coin-ish BigIntegers into Coin class.

---
 .../core/AbstractWalletEventListener.java     |   5 +-
 .../java/com/google/bitcoin/core/Block.java   |  10 +-
 .../java/com/google/bitcoin/core/Coin.java    | 132 +++++++
 .../bitcoin/core/FullPrunedBlockChain.java    |  17 +-
 .../core/InsufficientMoneyException.java      |   7 +-
 .../bitcoin/core/NetworkParameters.java       |   2 +-
 .../com/google/bitcoin/core/PeerGroup.java    |   3 +-
 .../bitcoin/core/StoredTransactionOutput.java |  11 +-
 .../com/google/bitcoin/core/Transaction.java  |  31 +-
 .../google/bitcoin/core/TransactionInput.java |   7 +-
 .../bitcoin/core/TransactionOutput.java       |  37 +-
 .../java/com/google/bitcoin/core/Utils.java   |  28 +-
 .../java/com/google/bitcoin/core/Wallet.java  | 134 +++----
 .../bitcoin/core/WalletEventListener.java     |   5 +-
 ...ntChannelServerConnectionEventHandler.java |   4 +-
 .../jni/NativeWalletEventListener.java        |   6 +-
 .../channels/IPaymentChannelClient.java       |   8 +-
 .../channels/PaymentChannelClient.java        |  27 +-
 .../PaymentChannelClientConnection.java       |   9 +-
 .../channels/PaymentChannelClientState.java   |  37 +-
 .../channels/PaymentChannelServer.java        |  13 +-
 .../PaymentChannelServerListener.java         |  10 +-
 .../channels/PaymentChannelServerState.java   |  23 +-
 .../ServerConnectionEventHandler.java         |   6 +-
 .../StoredPaymentChannelClientStates.java     |  17 +-
 .../StoredPaymentChannelServerStates.java     |   3 +-
 .../channels/StoredServerChannel.java         |  11 +-
 .../protocols/payments/PaymentProtocol.java   |  12 +-
 .../protocols/payments/PaymentSession.java    |  11 +-
 .../bitcoin/store/H2FullPrunedBlockStore.java |   2 +-
 .../store/PostgresFullPrunedBlockStore.java   |   2 +-
 .../store/WalletProtobufSerializer.java       |   4 +-
 .../google/bitcoin/testing/FakeTxBuilder.java |  11 +-
 .../testing/TestWithNetworkConnections.java   |   3 +-
 .../bitcoin/testing/TestWithWallet.java       |   9 +-
 .../com/google/bitcoin/uri/BitcoinURI.java    |  16 +-
 .../google/bitcoin/wallet/CoinSelection.java  |   8 +-
 .../google/bitcoin/wallet/CoinSelector.java   |   4 +-
 .../bitcoin/wallet/DefaultCoinSelector.java   |  13 +-
 .../bitcoin/wallet/DefaultRiskAnalysis.java   |   5 +-
 .../bitcoin/wallet/KeyTimeCoinSelector.java   |   5 +-
 .../bitcoin/protocols/payments/Protos.java    |   2 +-
 .../google/bitcoin/core/BlockChainTest.java   |   8 +-
 .../com/google/bitcoin/core/BlockTest.java    |   2 +-
 .../google/bitcoin/core/ChainSplitTest.java   |  17 +-
 .../bitcoin/core/CoinbaseBlockTest.java       |   6 +-
 .../bitcoin/core/FullBlockTestGenerator.java  | 180 +++++-----
 .../google/bitcoin/core/PeerGroupTest.java    |   3 +-
 .../com/google/bitcoin/core/PeerTest.java     |  13 +-
 .../com/google/bitcoin/core/UtilsTest.java    |   7 +-
 .../com/google/bitcoin/core/WalletTest.java   | 330 +++++++++---------
 .../channels/ChannelConnectionTest.java       |  33 +-
 .../protocols/channels/ChannelTestUtils.java  |   9 +-
 .../channels/PaymentChannelStateTest.java     |  74 ++--
 .../payments/PaymentProtocolTest.java         |   6 +-
 .../payments/PaymentSessionTest.java          |   5 +-
 .../store/WalletProtobufSerializerTest.java   |  10 +-
 .../wallet/DefaultCoinSelectorTest.java       |   3 +-
 .../wallet/DefaultRiskAnalysisTest.java       |   4 +-
 .../google/bitcoin/examples/DoubleSpend.java  |   3 +-
 .../examples/ExamplePaymentChannelClient.java |  13 +-
 .../examples/ExamplePaymentChannelServer.java |   7 +-
 .../bitcoin/examples/ForwardingService.java   |   9 +-
 .../bitcoin/examples/RefreshWallet.java       |   3 +-
 .../google/bitcoin/tools/TestFeeLevel.java    |   5 +-
 .../com/google/bitcoin/tools/WalletTool.java  |  20 +-
 66 files changed, 793 insertions(+), 687 deletions(-)
 create mode 100644 core/src/main/java/com/google/bitcoin/core/Coin.java

diff --git a/core/src/main/java/com/google/bitcoin/core/AbstractWalletEventListener.java b/core/src/main/java/com/google/bitcoin/core/AbstractWalletEventListener.java
index acccf17f..7f98d005 100644
--- a/core/src/main/java/com/google/bitcoin/core/AbstractWalletEventListener.java
+++ b/core/src/main/java/com/google/bitcoin/core/AbstractWalletEventListener.java
@@ -19,7 +19,6 @@ package com.google.bitcoin.core;
 import com.google.bitcoin.script.Script;
 import com.google.bitcoin.wallet.AbstractKeyChainEventListener;
 
-import java.math.BigInteger;
 import java.util.List;
 
 /**
@@ -27,12 +26,12 @@ import java.util.List;
  */
 public abstract class AbstractWalletEventListener extends AbstractKeyChainEventListener implements WalletEventListener {
     @Override
-    public void onCoinsReceived(Wallet wallet, Transaction tx, BigInteger prevBalance, BigInteger newBalance) {
+    public void onCoinsReceived(Wallet wallet, Transaction tx, Coin prevBalance, Coin newBalance) {
         onChange();
     }
 
     @Override
-    public void onCoinsSent(Wallet wallet, Transaction tx, BigInteger prevBalance, BigInteger newBalance) {
+    public void onCoinsSent(Wallet wallet, Transaction tx, Coin prevBalance, Coin newBalance) {
         onChange();
     }
 
diff --git a/core/src/main/java/com/google/bitcoin/core/Block.java b/core/src/main/java/com/google/bitcoin/core/Block.java
index da259c53..a36b3a16 100644
--- a/core/src/main/java/com/google/bitcoin/core/Block.java
+++ b/core/src/main/java/com/google/bitcoin/core/Block.java
@@ -166,7 +166,7 @@ public class Block extends Message {
      * <p>The half-life is controlled by {@link com.google.bitcoin.core.NetworkParameters#getSubsidyDecreaseBlockCount()}.
      * </p>
      */
-    public BigInteger getBlockInflation(int height) {
+    public Coin getBlockInflation(int height) {
         return Utils.toNanoCoins(50, 0).shiftRight(height / params.getSubsidyDecreaseBlockCount());
     }
 
@@ -953,7 +953,7 @@ public class Block extends Message {
     static private int txCounter;
 
     /** Adds a coinbase transaction to the block. This exists for unit tests. */
-    void addCoinbaseTransaction(byte[] pubKeyTo, BigInteger value) {
+    void addCoinbaseTransaction(byte[] pubKeyTo, Coin value) {
         unCacheTransactions();
         transactions = new ArrayList<Transaction>();
         Transaction coinbase = new Transaction(params);
@@ -989,7 +989,7 @@ public class Block extends Message {
      * In this variant you can specify a public key (pubkey) for use in generating coinbase blocks.
      */
     Block createNextBlock(@Nullable Address to, @Nullable TransactionOutPoint prevOut, long time,
-                          byte[] pubKey, BigInteger coinbaseValue) {
+                          byte[] pubKey, Coin coinbaseValue) {
         Block b = new Block(params);
         b.setDifficultyTarget(difficultyTarget);
         b.addCoinbaseTransaction(pubKey, coinbaseValue);
@@ -1036,7 +1036,7 @@ public class Block extends Message {
     }
 
     @VisibleForTesting
-    public Block createNextBlock(@Nullable Address to, BigInteger value) {
+    public Block createNextBlock(@Nullable Address to, Coin value) {
         return createNextBlock(to, null, Utils.currentTimeSeconds(), pubkeyForTesting, value);
     }
 
@@ -1046,7 +1046,7 @@ public class Block extends Message {
     }
 
     @VisibleForTesting
-    public Block createNextBlockWithCoinbase(byte[] pubKey, BigInteger coinbaseValue) {
+    public Block createNextBlockWithCoinbase(byte[] pubKey, Coin coinbaseValue) {
         return createNextBlock(null, null, Utils.currentTimeSeconds(), pubKey, coinbaseValue);
     }
 
diff --git a/core/src/main/java/com/google/bitcoin/core/Coin.java b/core/src/main/java/com/google/bitcoin/core/Coin.java
new file mode 100644
index 00000000..86f11903
--- /dev/null
+++ b/core/src/main/java/com/google/bitcoin/core/Coin.java
@@ -0,0 +1,132 @@
+/**
+ * Copyright 2014 Andreas Schildbach
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.google.bitcoin.core;
+
+import java.io.Serializable;
+import java.math.BigInteger;
+
+/**
+ * Represents a monetary Bitcoin value. This class is immutable.
+ */
+public final class Coin implements Comparable<Coin>, Serializable {
+
+    public static final Coin ZERO = new Coin(BigInteger.ZERO);
+    public static final Coin ONE = new Coin(BigInteger.ONE);
+    public static final Coin TEN = new Coin(BigInteger.TEN);
+
+    private final BigInteger value;
+
+    public Coin(final BigInteger value) {
+        this.value = value;
+    }
+
+    public Coin(final String value, final int radix) {
+        this(new BigInteger(value, radix));
+    }
+
+    public Coin(final byte[] value) {
+        this(new BigInteger(value));
+    }
+
+    public static Coin valueOf(final long value) {
+        return new Coin(BigInteger.valueOf(value));
+    }
+
+    public Coin add(final Coin value) {
+        return new Coin(this.value.add(value.value));
+    }
+
+    public Coin subtract(final Coin value) {
+        return new Coin(this.value.subtract(value.value));
+    }
+
+    public Coin multiply(final Coin value) {
+        return new Coin(this.value.multiply(value.value));
+    }
+
+    public Coin multiply(final long value) {
+        return multiply(Coin.valueOf(value));
+    }
+
+    public Coin divide(final Coin value) {
+        return new Coin(this.value.divide(value.value));
+    }
+
+    public Coin[] divideAndRemainder(final Coin value) {
+        final BigInteger[] result = this.value.divideAndRemainder(value.value);
+        return new Coin[] { new Coin(result[0]), new Coin(result[1]) };
+    }
+
+    public Coin shiftLeft(final int n) {
+        return new Coin(this.value.shiftLeft(n));
+    }
+
+    public Coin shiftRight(final int n) {
+        return new Coin(this.value.shiftRight(n));
+    }
+
+    public int signum() {
+        return this.value.signum();
+    }
+
+    public Coin negate() {
+        return new Coin(this.value.negate());
+    }
+
+    public byte[] toByteArray() {
+        return this.value.toByteArray();
+    }
+
+    public long longValue() {
+        return this.value.longValue();
+    }
+
+    public double doubleValue() {
+        return this.value.doubleValue();
+    }
+
+    public BigInteger toBigInteger() {
+        return value;
+    }
+
+    @Override
+    public String toString() {
+        return value.toString();
+    }
+
+    @Override
+    public boolean equals(final Object o) {
+        if (o == this)
+            return true;
+        if (o == null || o.getClass() != getClass())
+            return false;
+        final Coin other = (Coin) o;
+        if (!this.value.equals(other.value))
+            return false;
+        return true;
+    }
+
+    @Override
+    public int hashCode() {
+        return this.value.hashCode();
+    }
+
+    @Override
+    public int compareTo(final Coin other) {
+        return this.value.compareTo(other.value);
+    }
+}
diff --git a/core/src/main/java/com/google/bitcoin/core/FullPrunedBlockChain.java b/core/src/main/java/com/google/bitcoin/core/FullPrunedBlockChain.java
index aa008280..cb37323a 100644
--- a/core/src/main/java/com/google/bitcoin/core/FullPrunedBlockChain.java
+++ b/core/src/main/java/com/google/bitcoin/core/FullPrunedBlockChain.java
@@ -23,7 +23,6 @@ import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
 import javax.annotation.Nullable;
-import java.math.BigInteger;
 import java.util.ArrayList;
 import java.util.LinkedList;
 import java.util.List;
@@ -175,12 +174,12 @@ public class FullPrunedBlockChain extends AbstractBlockChain {
                         sigOps += tx.getSigOpCount();
                 }
             }
-            BigInteger totalFees = BigInteger.ZERO;
-            BigInteger coinbaseValue = null;
+            Coin totalFees = Coin.ZERO;
+            Coin coinbaseValue = null;
             for (final Transaction tx : block.transactions) {
                 boolean isCoinBase = tx.isCoinBase();
-                BigInteger valueIn = BigInteger.ZERO;
-                BigInteger valueOut = BigInteger.ZERO;
+                Coin valueIn = Coin.ZERO;
+                Coin valueOut = Coin.ZERO;
                 final List<Script> prevOutScripts = new LinkedList<Script>();
                 if (!isCoinBase) {
                     // For each input of the transaction remove the corresponding output from the set of unspent
@@ -300,16 +299,16 @@ public class FullPrunedBlockChain extends AbstractBlockChain {
                             throw new VerificationException("Block failed BIP30 test!");
                     }
                 }
-                BigInteger totalFees = BigInteger.ZERO;
-                BigInteger coinbaseValue = null;
+                Coin totalFees = Coin.ZERO;
+                Coin coinbaseValue = null;
                 
                 if (scriptVerificationExecutor.isShutdown())
                     scriptVerificationExecutor = Executors.newFixedThreadPool(Runtime.getRuntime().availableProcessors());
                 List<Future<VerificationException>> listScriptVerificationResults = new ArrayList<Future<VerificationException>>(transactions.size());
                 for(final Transaction tx : transactions) {
                     boolean isCoinBase = tx.isCoinBase();
-                    BigInteger valueIn = BigInteger.ZERO;
-                    BigInteger valueOut = BigInteger.ZERO;
+                    Coin valueIn = Coin.ZERO;
+                    Coin valueOut = Coin.ZERO;
                     final List<Script> prevOutScripts = new LinkedList<Script>();
                     if (!isCoinBase) {
                         for (int index = 0; index < tx.getInputs().size(); index++) {
diff --git a/core/src/main/java/com/google/bitcoin/core/InsufficientMoneyException.java b/core/src/main/java/com/google/bitcoin/core/InsufficientMoneyException.java
index c42b66ac..03858941 100644
--- a/core/src/main/java/com/google/bitcoin/core/InsufficientMoneyException.java
+++ b/core/src/main/java/com/google/bitcoin/core/InsufficientMoneyException.java
@@ -17,7 +17,6 @@
 package com.google.bitcoin.core;
 
 import javax.annotation.Nullable;
-import java.math.BigInteger;
 
 import static com.google.common.base.Preconditions.checkNotNull;
 
@@ -27,17 +26,17 @@ import static com.google.common.base.Preconditions.checkNotNull;
 public class InsufficientMoneyException extends Exception {
     /** Contains the number of satoshis that would have been required to complete the operation. */
     @Nullable
-    public final BigInteger missing;
+    public final Coin missing;
 
     protected InsufficientMoneyException() {
         this.missing = null;
     }
 
-    public InsufficientMoneyException(BigInteger missing) {
+    public InsufficientMoneyException(Coin missing) {
         this(missing, "Insufficient money,  missing " + missing + " satoshis");
     }
 
-    public InsufficientMoneyException(BigInteger missing, String message) {
+    public InsufficientMoneyException(Coin missing, String message) {
         super(message);
         this.missing = checkNotNull(missing);
     }
diff --git a/core/src/main/java/com/google/bitcoin/core/NetworkParameters.java b/core/src/main/java/com/google/bitcoin/core/NetworkParameters.java
index f080f9c1..2e636ef7 100644
--- a/core/src/main/java/com/google/bitcoin/core/NetworkParameters.java
+++ b/core/src/main/java/com/google/bitcoin/core/NetworkParameters.java
@@ -133,7 +133,7 @@ public abstract class NetworkParameters implements Serializable {
     /**
      * The maximum money to be generated
      */
-    public static final BigInteger MAX_MONEY = new BigInteger("21000000", 10).multiply(COIN);
+    public static final Coin MAX_MONEY = new Coin("21000000", 10).multiply(COIN);
 
     /** Alias for TestNet3Params.get(), use that instead. */
     @Deprecated
diff --git a/core/src/main/java/com/google/bitcoin/core/PeerGroup.java b/core/src/main/java/com/google/bitcoin/core/PeerGroup.java
index 548c2e2b..610bc5f9 100644
--- a/core/src/main/java/com/google/bitcoin/core/PeerGroup.java
+++ b/core/src/main/java/com/google/bitcoin/core/PeerGroup.java
@@ -45,7 +45,6 @@ import javax.annotation.Nullable;
 import java.lang.reflect.Constructor;
 import java.lang.reflect.Field;
 import java.lang.reflect.Method;
-import java.math.BigInteger;
 import java.net.InetAddress;
 import java.net.InetSocketAddress;
 import java.util.*;
@@ -179,7 +178,7 @@ public class PeerGroup extends AbstractExecutionThreadService implements Transac
         }
 
         @Override
-        public void onCoinsReceived(Wallet wallet, Transaction tx, BigInteger prevBalance, BigInteger newBalance) {
+        public void onCoinsReceived(Wallet wallet, Transaction tx, Coin prevBalance, Coin newBalance) {
             // We received a relevant transaction. We MAY need to recalculate and resend the Bloom filter, but only
             // if we have received a transaction that includes a relevant pay-to-pubkey output.
             //
diff --git a/core/src/main/java/com/google/bitcoin/core/StoredTransactionOutput.java b/core/src/main/java/com/google/bitcoin/core/StoredTransactionOutput.java
index 3737b535..85d10000 100644
--- a/core/src/main/java/com/google/bitcoin/core/StoredTransactionOutput.java
+++ b/core/src/main/java/com/google/bitcoin/core/StoredTransactionOutput.java
@@ -17,7 +17,6 @@
 package com.google.bitcoin.core;
 
 import java.io.*;
-import java.math.BigInteger;
 
 /**
  * A StoredTransactionOutput message contains the information necessary to check a spending transaction.
@@ -31,7 +30,7 @@ public class StoredTransactionOutput implements Serializable {
      *  A transaction output has some value and a script used for authenticating that the redeemer is allowed to spend
      *  this output.
      */
-    private BigInteger value;
+    private Coin value;
     private byte[] scriptBytes;
 
     /** Hash of the transaction to which we refer. */
@@ -53,7 +52,7 @@ public class StoredTransactionOutput implements Serializable {
      * @param height the height this output was created in
      * @param scriptBytes
      */
-    public StoredTransactionOutput(Sha256Hash hash, long index, BigInteger value, int height, boolean isCoinbase, byte[] scriptBytes) {
+    public StoredTransactionOutput(Sha256Hash hash, long index, Coin value, int height, boolean isCoinbase, byte[] scriptBytes) {
         this.hash = hash;
         this.index = index;
         this.value = value;
@@ -73,7 +72,7 @@ public class StoredTransactionOutput implements Serializable {
         byte[] valueBytes = new byte[8];
         if (in.read(valueBytes, 0, 8) != 8)
             throw new EOFException();
-        value = BigInteger.valueOf(Utils.readInt64(valueBytes, 0));
+        value = Coin.valueOf(Utils.readInt64(valueBytes, 0));
         
         int scriptBytesLength = ((in.read() & 0xFF) << 0) |
                                 ((in.read() & 0xFF) << 8) |
@@ -103,7 +102,7 @@ public class StoredTransactionOutput implements Serializable {
      * The value which this Transaction output holds
      * @return the value
      */
-    public BigInteger getValue() {
+    public Coin getValue() {
         return value;
     }
 
@@ -157,7 +156,7 @@ public class StoredTransactionOutput implements Serializable {
     }
 
     public void serializeToStream(OutputStream bos) throws IOException {
-        Utils.uint64ToByteStreamLE(value, bos);
+        Utils.uint64ToByteStreamLE(value.toBigInteger(), bos);
         
         bos.write(0xFF & scriptBytes.length >> 0);
         bos.write(0xFF & scriptBytes.length >> 8);
diff --git a/core/src/main/java/com/google/bitcoin/core/Transaction.java b/core/src/main/java/com/google/bitcoin/core/Transaction.java
index 5d9092c0..0b94a34c 100644
--- a/core/src/main/java/com/google/bitcoin/core/Transaction.java
+++ b/core/src/main/java/com/google/bitcoin/core/Transaction.java
@@ -33,7 +33,6 @@ import org.spongycastle.crypto.params.KeyParameter;
 
 import javax.annotation.Nullable;
 import java.io.*;
-import java.math.BigInteger;
 import java.text.ParseException;
 import java.text.SimpleDateFormat;
 import java.util.*;
@@ -87,14 +86,14 @@ public class Transaction extends ChildMessage implements Serializable {
      * If fee is lower than this value (in satoshis), a default reference client will treat it as if there were no fee.
      * Currently this is 10000 satoshis.
      */
-    public static final BigInteger REFERENCE_DEFAULT_MIN_TX_FEE = BigInteger.valueOf(10000);
+    public static final Coin REFERENCE_DEFAULT_MIN_TX_FEE = Coin.valueOf(10000);
 
     /**
      * Any standard (ie pay-to-address) output smaller than this value (in satoshis) will most likely be rejected by the network.
      * This is calculated by assuming a standard output will be 34 bytes, and then using the formula used in
-     * {@link TransactionOutput#getMinNonDustValue(BigInteger)}. Currently it's 5460 satoshis.
+     * {@link TransactionOutput#getMinNonDustValue(Coin)}. Currently it's 5460 satoshis.
      */
-    public static final BigInteger MIN_NONDUST_OUTPUT = BigInteger.valueOf(5460);
+    public static final Coin MIN_NONDUST_OUTPUT = Coin.valueOf(5460);
 
     // These are serialized in both bitcoin and java serialization.
     private long version;
@@ -237,10 +236,10 @@ public class Transaction extends ChildMessage implements Serializable {
      * Calculates the sum of the outputs that are sending coins to a key in the wallet. The flag controls whether to
      * include spent outputs or not.
      */
-    BigInteger getValueSentToMe(Wallet wallet, boolean includeSpent) {
+    Coin getValueSentToMe(Wallet wallet, boolean includeSpent) {
         maybeParse();
         // This is tested in WalletTest.
-        BigInteger v = BigInteger.ZERO;
+        Coin v = Coin.ZERO;
         for (TransactionOutput o : outputs) {
             if (!o.isMineOrWatched(wallet)) continue;
             if (!includeSpent && !o.isAvailableForSpending()) continue;
@@ -275,7 +274,7 @@ public class Transaction extends ChildMessage implements Serializable {
     /**
      * Calculates the sum of the outputs that are sending coins to a key in the wallet.
      */
-    public BigInteger getValueSentToMe(Wallet wallet) {
+    public Coin getValueSentToMe(Wallet wallet) {
         return getValueSentToMe(wallet, true);
     }
 
@@ -347,10 +346,10 @@ public class Transaction extends ChildMessage implements Serializable {
      *
      * @return sum in nanocoins.
      */
-    public BigInteger getValueSentFromMe(Wallet wallet) throws ScriptException {
+    public Coin getValueSentFromMe(Wallet wallet) throws ScriptException {
         maybeParse();
         // This is tested in WalletTest.
-        BigInteger v = BigInteger.ZERO;
+        Coin v = Coin.ZERO;
         for (TransactionInput input : inputs) {
             // This input is taking value from a transaction in our wallet. To discover the value,
             // we must find the connected transaction.
@@ -373,7 +372,7 @@ public class Transaction extends ChildMessage implements Serializable {
     /**
      * Returns the difference of {@link Transaction#getValueSentFromMe(Wallet)} and {@link Transaction#getValueSentToMe(Wallet)}.
      */
-    public BigInteger getValue(Wallet wallet) throws ScriptException {
+    public Coin getValue(Wallet wallet) throws ScriptException {
         return getValueSentToMe(wallet).subtract(getValueSentFromMe(wallet));
     }
 
@@ -383,8 +382,8 @@ public class Transaction extends ChildMessage implements Serializable {
      * 
      * @return fee, or null if it cannot be determined
      */
-    public BigInteger getFee() {
-        BigInteger fee = BigInteger.ZERO;
+    public Coin getFee() {
+        Coin fee = Coin.ZERO;
         for (TransactionInput input : inputs) {
             if (input.getValue() == null)
                 return null;
@@ -807,7 +806,7 @@ public class Transaction extends ChildMessage implements Serializable {
     /**
      * Creates an output based on the given address and value, adds it to this transaction, and returns the new output.
      */
-    public TransactionOutput addOutput(BigInteger value, Address address) {
+    public TransactionOutput addOutput(Coin value, Address address) {
         return addOutput(new TransactionOutput(params, this, value, address));
     }
 
@@ -815,7 +814,7 @@ public class Transaction extends ChildMessage implements Serializable {
      * Creates an output that pays to the given pubkey directly (no address) with the given value, adds it to this
      * transaction, and returns the new output.
      */
-    public TransactionOutput addOutput(BigInteger value, ECKey pubkey) {
+    public TransactionOutput addOutput(Coin value, ECKey pubkey) {
         return addOutput(new TransactionOutput(params, this, value, pubkey));
     }
 
@@ -823,7 +822,7 @@ public class Transaction extends ChildMessage implements Serializable {
      * Creates an output that pays to the given script. The address and key forms are specialisations of this method,
      * you won't normally need to use it unless you're doing unusual things.
      */
-    public TransactionOutput addOutput(BigInteger value, Script script) {
+    public TransactionOutput addOutput(Coin value, Script script) {
         return addOutput(new TransactionOutput(params, this, value, script.getProgram()));
     }
 
@@ -1263,7 +1262,7 @@ public class Transaction extends ChildMessage implements Serializable {
         if (this.getMessageSize() > Block.MAX_BLOCK_SIZE)
             throw new VerificationException("Transaction larger than MAX_BLOCK_SIZE");
 
-        BigInteger valueOut = BigInteger.ZERO;
+        Coin valueOut = Coin.ZERO;
         for (TransactionOutput output : outputs) {
             if (output.getValue().signum() < 0)
                 throw new VerificationException("Transaction output negative");
diff --git a/core/src/main/java/com/google/bitcoin/core/TransactionInput.java b/core/src/main/java/com/google/bitcoin/core/TransactionInput.java
index 08525c59..b9c41a26 100644
--- a/core/src/main/java/com/google/bitcoin/core/TransactionInput.java
+++ b/core/src/main/java/com/google/bitcoin/core/TransactionInput.java
@@ -25,7 +25,6 @@ import java.io.ObjectOutputStream;
 import java.io.OutputStream;
 import java.io.Serializable;
 import java.lang.ref.WeakReference;
-import java.math.BigInteger;
 import java.util.Arrays;
 import java.util.Map;
 
@@ -58,7 +57,7 @@ public class TransactionInput extends ChildMessage implements Serializable {
     transient private WeakReference<Script> scriptSig;
     /** Value of the output connected to the input, if known. This field does not participate in equals()/hashCode(). */
     @Nullable
-    private final BigInteger value;
+    private final Coin value;
     // A pointer to the transaction that owns this input.
     private final Transaction parentTransaction;
 
@@ -75,7 +74,7 @@ public class TransactionInput extends ChildMessage implements Serializable {
     }
 
     public TransactionInput(NetworkParameters params, @Nullable Transaction parentTransaction, byte[] scriptBytes,
-            TransactionOutPoint outpoint, @Nullable BigInteger value) {
+            TransactionOutPoint outpoint, @Nullable Coin value) {
         super(params);
         this.scriptBytes = scriptBytes;
         this.outpoint = outpoint;
@@ -267,7 +266,7 @@ public class TransactionInput extends ChildMessage implements Serializable {
      * @return Value of the output connected to this input, if known. Null if unknown.
      */
     @Nullable
-    public BigInteger getValue() {
+    public Coin getValue() {
         return value;
     }
 
diff --git a/core/src/main/java/com/google/bitcoin/core/TransactionOutput.java b/core/src/main/java/com/google/bitcoin/core/TransactionOutput.java
index f6c3b746..cc257c2f 100644
--- a/core/src/main/java/com/google/bitcoin/core/TransactionOutput.java
+++ b/core/src/main/java/com/google/bitcoin/core/TransactionOutput.java
@@ -18,16 +18,17 @@ package com.google.bitcoin.core;
 
 import com.google.bitcoin.script.Script;
 import com.google.bitcoin.script.ScriptBuilder;
+
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
 import javax.annotation.Nullable;
+
 import java.io.IOException;
 import java.io.ObjectOutputStream;
 import java.io.OutputStream;
 import java.io.Serializable;
 import java.lang.ref.WeakReference;
-import java.math.BigInteger;
 import java.util.Arrays;
 
 import static com.google.common.base.Preconditions.*;
@@ -42,7 +43,7 @@ public class TransactionOutput extends ChildMessage implements Serializable {
 
     // A transaction output has some value and a script used for authenticating that the redeemer is allowed to spend
     // this output.
-    private BigInteger value;
+    private Coin value;
     private byte[] scriptBytes;
 
     // The script bytes are parsed and turned into a Script on demand.
@@ -91,22 +92,22 @@ public class TransactionOutput extends ChildMessage implements Serializable {
     /**
      * Creates an output that sends 'value' to the given address (public key hash). The amount should be created with
      * something like {@link Utils#toNanoCoins(int, int)}. Typically you would use
-     * {@link Transaction#addOutput(java.math.BigInteger, Address)} instead of creating a TransactionOutput directly.
+     * {@link Transaction#addOutput(java.math.Coin, Address)} instead of creating a TransactionOutput directly.
      */
-    public TransactionOutput(NetworkParameters params, @Nullable Transaction parent, BigInteger value, Address to) {
+    public TransactionOutput(NetworkParameters params, @Nullable Transaction parent, Coin value, Address to) {
         this(params, parent, value, ScriptBuilder.createOutputScript(to).getProgram());
     }
 
     /**
      * Creates an output that sends 'value' to the given public key using a simple CHECKSIG script (no addresses). The
      * amount should be created with something like {@link Utils#toNanoCoins(int, int)}. Typically you would use
-     * {@link Transaction#addOutput(java.math.BigInteger, ECKey)} instead of creating an output directly.
+     * {@link Transaction#addOutput(java.math.Coin, ECKey)} instead of creating an output directly.
      */
-    public TransactionOutput(NetworkParameters params, @Nullable Transaction parent, BigInteger value, ECKey to) {
+    public TransactionOutput(NetworkParameters params, @Nullable Transaction parent, Coin value, ECKey to) {
         this(params, parent, value, ScriptBuilder.createOutputScript(to).getProgram());
     }
 
-    public TransactionOutput(NetworkParameters params, @Nullable Transaction parent, BigInteger value, byte[] scriptBytes) {
+    public TransactionOutput(NetworkParameters params, @Nullable Transaction parent, Coin value, byte[] scriptBytes) {
         super(params);
         // Negative values obviously make no sense, except for -1 which is used as a sentinel value when calculating
         // SIGHASH_SINGLE signatures, so unfortunately we have to allow that here.
@@ -134,11 +135,11 @@ public class TransactionOutput extends ChildMessage implements Serializable {
     }
 
     protected void parseLite() throws ProtocolException {
-        // TODO: There is no reason to use BigInteger for values, they are always smaller than 21 million * COIN
-        // The only reason to use BigInteger would be to properly read values from the reference implementation, however
+        // TODO: There is no reason to use Coin for values, they are always smaller than 21 million * COIN
+        // The only reason to use Coin would be to properly read values from the reference implementation, however
         // the reference implementation uses signed 64-bit integers for its values as well (though it probably shouldn't)
         long outputValue = readInt64();
-        value = BigInteger.valueOf(outputValue);
+        value = Coin.valueOf(outputValue);
         scriptLen = (int) readVarInt();
         length = cursor - offset + scriptLen;
     }
@@ -160,7 +161,7 @@ public class TransactionOutput extends ChildMessage implements Serializable {
      * Returns the value of this output in nanocoins. This is the amount of currency that the destination address
      * receives.
      */
-    public BigInteger getValue() {
+    public Coin getValue() {
         maybeParse();
         return value;
     }
@@ -168,7 +169,7 @@ public class TransactionOutput extends ChildMessage implements Serializable {
     /**
      * Sets the value of this output in nanocoins.
      */
-    public void setValue(BigInteger value) {
+    public void setValue(Coin value) {
         checkNotNull(value);
         unCache();
         this.value = value;
@@ -197,15 +198,15 @@ public class TransactionOutput extends ChildMessage implements Serializable {
      * @param feePerKbRequired The fee required per kilobyte. Note that this is the same as the reference client's -minrelaytxfee * 3
      *                         If you want a safe default, use {@link Transaction#REFERENCE_DEFAULT_MIN_TX_FEE}*3
      */
-    public BigInteger getMinNonDustValue(BigInteger feePerKbRequired) {
+    public Coin getMinNonDustValue(Coin feePerKbRequired) {
         // A typical output is 33 bytes (pubkey hash + opcodes) and requires an input of 148 bytes to spend so we add
         // that together to find out the total amount of data used to transfer this amount of value. Note that this
         // formula is wrong for anything that's not a pay-to-address output, unfortunately, we must follow the reference
         // clients wrongness in order to ensure we're considered standard. A better formula would either estimate the
         // size of data needed to satisfy all different script types, or just hard code 33 below.
-        final BigInteger size = BigInteger.valueOf(this.bitcoinSerialize().length + 148);
-        BigInteger[] nonDustAndRemainder = feePerKbRequired.multiply(size).divideAndRemainder(BigInteger.valueOf(1000));
-        return nonDustAndRemainder[1].equals(BigInteger.ZERO) ? nonDustAndRemainder[0] : nonDustAndRemainder[0].add(BigInteger.ONE);
+        final long size = this.bitcoinSerialize().length + 148;
+        Coin[] nonDustAndRemainder = feePerKbRequired.multiply(size).divideAndRemainder(Coin.valueOf(1000));
+        return nonDustAndRemainder[1].equals(Coin.ZERO) ? nonDustAndRemainder[0] : nonDustAndRemainder[0].add(Coin.ONE);
     }
 
     /**
@@ -213,8 +214,8 @@ public class TransactionOutput extends ChildMessage implements Serializable {
      * and mined by default miners. For normal pay to address outputs, this is 5460 satoshis, the same as
      * {@link Transaction#MIN_NONDUST_OUTPUT}.
      */
-    public BigInteger getMinNonDustValue() {
-        return getMinNonDustValue(Transaction.REFERENCE_DEFAULT_MIN_TX_FEE.multiply(BigInteger.valueOf(3)));
+    public Coin getMinNonDustValue() {
+        return getMinNonDustValue(Transaction.REFERENCE_DEFAULT_MIN_TX_FEE.multiply(Coin.valueOf(3)));
     }
 
     /**
diff --git a/core/src/main/java/com/google/bitcoin/core/Utils.java b/core/src/main/java/com/google/bitcoin/core/Utils.java
index 4183639e..192bed3a 100644
--- a/core/src/main/java/com/google/bitcoin/core/Utils.java
+++ b/core/src/main/java/com/google/bitcoin/core/Utils.java
@@ -45,7 +45,7 @@ import static com.google.common.util.concurrent.Uninterruptibles.sleepUninterrup
  * To enable debug logging from the library, run with -Dbitcoinj.logging=true on your command line.
  */
 public class Utils {
-    public static final BigInteger NEGATIVE_ONE = BigInteger.valueOf(-1);
+    public static final Coin NEGATIVE_ONE = Coin.valueOf(-1);
     private static final MessageDigest digest;
     static {
         try {
@@ -68,7 +68,7 @@ public class Utils {
      * The term nanocoin is very misleading, though, because there are only 100 million
      * of them in a coin (whereas one would expect 1 billion.
      */
-    public static final BigInteger COIN = new BigInteger("100000000", 10);
+    public static final Coin COIN = new Coin("100000000", 10);
 
     /**
      * How many "nanocoins" there are in 0.01 BitCoins.
@@ -77,19 +77,19 @@ public class Utils {
      * The term nanocoin is very misleading, though, because there are only 100 million
      * of them in a coin (whereas one would expect 1 billion).
      */
-    public static final BigInteger CENT = new BigInteger("1000000", 10);
+    public static final Coin CENT = new Coin("1000000", 10);
     private static BlockingQueue<Boolean> mockSleepQueue;
 
     /**
      * Convert an amount expressed in the way humans are used to into nanocoins.
      */
-    public static BigInteger toNanoCoins(int coins, int cents) {
+    public static Coin toNanoCoins(int coins, int cents) {
         checkArgument(cents < 100);
         checkArgument(cents >= 0);
         checkArgument(coins >= 0);
         checkArgument(coins < NetworkParameters.MAX_MONEY.divide(Utils.COIN).longValue());
-        BigInteger bi = BigInteger.valueOf(coins).multiply(COIN);
-        bi = bi.add(BigInteger.valueOf(cents).multiply(CENT));
+        Coin bi = Coin.valueOf(coins).multiply(COIN);
+        bi = bi.add(Coin.valueOf(cents).multiply(CENT));
         return bi;
     }
 
@@ -121,12 +121,12 @@ public class Utils {
      *
      * @throws ArithmeticException if you try to specify fractional nanocoins, or nanocoins out of range.
      */
-    public static BigInteger toNanoCoins(String coins) {
-        BigInteger bigint = new BigDecimal(coins).movePointRight(8).toBigIntegerExact();
+    public static Coin toNanoCoins(String coins) {
+        Coin bigint = new Coin(new BigDecimal(coins).movePointRight(8).toBigIntegerExact());
         if (bigint.signum() < 0)
             throw new ArithmeticException("Negative coins specified");
         if (bigint.compareTo(NetworkParameters.MAX_MONEY) > 0)
-            throw new ArithmeticException("Amount larger than the total quantity of Bitcoins possible specified.");
+            throw new ArithmeticException("Coin larger than the total quantity of Bitcoins possible specified.");
         return bigint;
     }
 
@@ -332,12 +332,12 @@ public class Utils {
      * Returns the given value in nanocoins as a 0.12 type string. More digits after the decimal place will be used
      * if necessary, but two will always be present.
      */
-    public static String bitcoinValueToFriendlyString(BigInteger value) {
+    public static String bitcoinValueToFriendlyString(Coin value) {
         // TODO: This API is crap. This method should go away when we encapsulate money values.
         boolean negative = value.signum() < 0;
         if (negative)
             value = value.negate();
-        BigDecimal bd = new BigDecimal(value, 8);
+        BigDecimal bd = new BigDecimal(value.toBigInteger(), 8);
         String formatted = bd.toPlainString();   // Don't use scientific notation.
         int decimalPoint = formatted.indexOf(".");
         // Drop unnecessary zeros from the end.
@@ -355,19 +355,19 @@ public class Utils {
      * <p>
      * Returns the given value as a plain string denominated in BTC.   
      * The result is unformatted with no trailing zeroes.
-     * For instance, an input value of BigInteger.valueOf(150000) nanocoin gives an output string of "0.0015" BTC
+     * For instance, an input value of Coin.valueOf(150000) nanocoin gives an output string of "0.0015" BTC
      * </p>
      * 
      * @param value The value in nanocoins to convert to a string (denominated in BTC)
      * @throws IllegalArgumentException
      *            If the input value is null
      */
-    public static String bitcoinValueToPlainString(BigInteger value) {
+    public static String bitcoinValueToPlainString(Coin value) {
         if (value == null) {
             throw new IllegalArgumentException("Value cannot be null");
         }
                 
-        BigDecimal valueInBTC = new BigDecimal(value).divide(new BigDecimal(Utils.COIN));
+        BigDecimal valueInBTC = new BigDecimal(value.toBigInteger()).divide(new BigDecimal(Utils.COIN.toBigInteger()));
         return valueInBTC.toPlainString();
     }
 
diff --git a/core/src/main/java/com/google/bitcoin/core/Wallet.java b/core/src/main/java/com/google/bitcoin/core/Wallet.java
index 417ebb99..5da4de8e 100644
--- a/core/src/main/java/com/google/bitcoin/core/Wallet.java
+++ b/core/src/main/java/com/google/bitcoin/core/Wallet.java
@@ -1094,8 +1094,8 @@ public class Wallet extends BaseTaggableObject implements Serializable, BlockCha
                 log.warn("There are now {} risk dropped transactions being kept in memory", riskDropped.size());
                 return;
             }
-            BigInteger valueSentToMe = tx.getValueSentToMe(this);
-            BigInteger valueSentFromMe = tx.getValueSentFromMe(this);
+            Coin valueSentToMe = tx.getValueSentToMe(this);
+            Coin valueSentFromMe = tx.getValueSentFromMe(this);
             if (log.isInfoEnabled()) {
                 log.info(String.format("Received a pending transaction %s that spends %s BTC from our own wallet," +
                         " and sends us %s BTC", tx.getHashAsString(), Utils.bitcoinValueToFriendlyString(valueSentFromMe),
@@ -1272,14 +1272,14 @@ public class Wallet extends BaseTaggableObject implements Serializable, BlockCha
                          int relativityOffset) throws VerificationException {
         // Runs in a peer thread.
         checkState(lock.isHeldByCurrentThread());
-        BigInteger prevBalance = getBalance();
+        Coin prevBalance = getBalance();
         Sha256Hash txHash = tx.getHash();
         boolean bestChain = blockType == BlockChain.NewBlockType.BEST_CHAIN;
         boolean sideChain = blockType == BlockChain.NewBlockType.SIDE_CHAIN;
 
-        BigInteger valueSentFromMe = tx.getValueSentFromMe(this);
-        BigInteger valueSentToMe = tx.getValueSentToMe(this);
-        BigInteger valueDifference = valueSentToMe.subtract(valueSentFromMe);
+        Coin valueSentFromMe = tx.getValueSentFromMe(this);
+        Coin valueSentToMe = tx.getValueSentToMe(this);
+        Coin valueDifference = valueSentToMe.subtract(valueSentFromMe);
 
         log.info("Received tx{} for {} BTC: {} [{}] in block {}", sideChain ? " on a side chain" : "",
                 bitcoinValueToFriendlyString(valueDifference), tx.getHashAsString(), relativityOffset,
@@ -1364,7 +1364,7 @@ public class Wallet extends BaseTaggableObject implements Serializable, BlockCha
         //    own spends. If users want to know when a broadcast tx becomes confirmed, they need to use tx confidence
         //    listeners.
         if (!insideReorg && bestChain) {
-            BigInteger newBalance = getBalance();  // This is slow.
+            Coin newBalance = getBalance();  // This is slow.
             log.info("Balance is now: " + bitcoinValueToFriendlyString(newBalance));
             if (!wasPending) {
                 int diff = valueDifference.signum();
@@ -1694,7 +1694,7 @@ public class Wallet extends BaseTaggableObject implements Serializable, BlockCha
             if (pending.containsKey(tx.getHash()))
                 return false;
             log.info("commitTx of {}", tx.getHashAsString());
-            BigInteger balance = getBalance();
+            Coin balance = getBalance();
             tx.setUpdateTime(Utils.now());
             // Mark the outputs we're spending as spent so we won't try and use them in future creations. This will also
             // move any transactions that are now fully spent to the spent map so we can skip them when creating future
@@ -1708,9 +1708,9 @@ public class Wallet extends BaseTaggableObject implements Serializable, BlockCha
             addWalletTransaction(Pool.PENDING, tx);
 
             try {
-                BigInteger valueSentFromMe = tx.getValueSentFromMe(this);
-                BigInteger valueSentToMe = tx.getValueSentToMe(this);
-                BigInteger newBalance = balance.add(valueSentToMe).subtract(valueSentFromMe);
+                Coin valueSentFromMe = tx.getValueSentFromMe(this);
+                Coin valueSentToMe = tx.getValueSentToMe(this);
+                Coin newBalance = balance.add(valueSentToMe).subtract(valueSentFromMe);
                 if (valueSentToMe.signum() > 0) {
                     checkBalanceFuturesLocked(null);
                     queueOnCoinsReceived(tx, balance, newBalance);
@@ -2015,7 +2015,7 @@ public class Wallet extends BaseTaggableObject implements Serializable, BlockCha
          * fees) - the wallet will calculate all that for you and update tx later.</p>
          *
          * <p>Be careful when adding outputs that you check the min output value
-         * ({@link TransactionOutput#getMinNonDustValue(BigInteger)}) to avoid the whole transaction being rejected
+         * ({@link TransactionOutput#getMinNonDustValue(Coin)}) to avoid the whole transaction being rejected
          * because one output is dust.</p>
          *
          * <p>If there are already inputs to the transaction, make sure their out point has a connected output,
@@ -2056,7 +2056,7 @@ public class Wallet extends BaseTaggableObject implements Serializable, BlockCha
          * <p>You might also consider adding a {@link SendRequest#feePerKb} to set the fee per kb of transaction size
          * (rounded down to the nearest kb) as that is how transactions are sorted when added to a block by miners.</p>
          */
-        public BigInteger fee = null;
+        public Coin fee = null;
 
         /**
          * <p>A transaction can have a fee attached, which is defined as the difference between the input values
@@ -2072,13 +2072,13 @@ public class Wallet extends BaseTaggableObject implements Serializable, BlockCha
          *
          * <p>You might also consider using a {@link SendRequest#fee} to set the fee added for the first kb of size.</p>
          */
-        public BigInteger feePerKb = DEFAULT_FEE_PER_KB;
+        public Coin feePerKb = DEFAULT_FEE_PER_KB;
 
         /**
          * If you want to modify the default fee for your entire app without having to change each SendRequest you make,
          * you can do it here. This is primarily useful for unit tests.
          */
-        public static BigInteger DEFAULT_FEE_PER_KB = Transaction.REFERENCE_DEFAULT_MIN_TX_FEE;
+        public static Coin DEFAULT_FEE_PER_KB = Transaction.REFERENCE_DEFAULT_MIN_TX_FEE;
 
         /**
          * <p>Requires that there be enough fee for a default reference client to at least relay the transaction.
@@ -2123,7 +2123,7 @@ public class Wallet extends BaseTaggableObject implements Serializable, BlockCha
          * <p>Be very careful when value is smaller than {@link Transaction#MIN_NONDUST_OUTPUT} as the transaction will
          * likely be rejected by the network in this case.</p>
          */
-        public static SendRequest to(Address destination, BigInteger value) {
+        public static SendRequest to(Address destination, Coin value) {
             SendRequest req = new SendRequest();
             final NetworkParameters parameters = destination.getParameters();
             checkNotNull(parameters, "Address is for an unknown network");
@@ -2136,11 +2136,11 @@ public class Wallet extends BaseTaggableObject implements Serializable, BlockCha
          * <p>Creates a new SendRequest to the given pubkey for the given value.</p>
          *
          * <p>Be careful to check the output's value is reasonable using
-         * {@link TransactionOutput#getMinNonDustValue(BigInteger)} afterwards or you risk having the transaction
-         * rejected by the network. Note that using {@link SendRequest#to(Address, java.math.BigInteger)} will result
+         * {@link TransactionOutput#getMinNonDustValue(Coin)} afterwards or you risk having the transaction
+         * rejected by the network. Note that using {@link SendRequest#to(Address, java.math.Coin)} will result
          * in a smaller output, and thus the ability to use a smaller output value without rejection.</p>
          */
-        public static SendRequest to(NetworkParameters params, ECKey destination, BigInteger value) {
+        public static SendRequest to(NetworkParameters params, ECKey destination, Coin value) {
             SendRequest req = new SendRequest();
             req.tx = new Transaction(params);
             req.tx.addOutput(value, destination);
@@ -2159,7 +2159,7 @@ public class Wallet extends BaseTaggableObject implements Serializable, BlockCha
             final NetworkParameters parameters = destination.getParameters();
             checkNotNull(parameters, "Address is for an unknown network");
             req.tx = new Transaction(parameters);
-            req.tx.addOutput(BigInteger.ZERO, destination);
+            req.tx.addOutput(Coin.ZERO, destination);
             req.emptyWallet = true;
             return req;
         }
@@ -2170,11 +2170,11 @@ public class Wallet extends BaseTaggableObject implements Serializable, BlockCha
      * {@link Wallet#getChangeAddress()}, so you must have added at least one key.</p>
      *
      * <p>If you just want to send money quickly, you probably want
-     * {@link Wallet#sendCoins(TransactionBroadcaster, Address, java.math.BigInteger)} instead. That will create the sending
+     * {@link Wallet#sendCoins(TransactionBroadcaster, Address, java.math.Coin)} instead. That will create the sending
      * transaction, commit to the wallet and broadcast it to the network all in one go. This method is lower level
      * and lets you see the proposed transaction before anything is done with it.</p>
      *
-     * <p>This is a helper method that is equivalent to using {@link Wallet.SendRequest#to(Address, java.math.BigInteger)}
+     * <p>This is a helper method that is equivalent to using {@link Wallet.SendRequest#to(Address, java.math.Coin)}
      * followed by {@link Wallet#completeTx(Wallet.SendRequest)} and returning the requests transaction object.
      * Note that this means a fee may be automatically added if required, if you want more control over the process,
      * just do those two steps yourself.</p>
@@ -2193,7 +2193,7 @@ public class Wallet extends BaseTaggableObject implements Serializable, BlockCha
      * coins as spent until commitTx is called on the result.
      * @throws InsufficientMoneyException if the request could not be completed due to not enough balance.
      */
-    public Transaction createSend(Address address, BigInteger nanocoins) throws InsufficientMoneyException {
+    public Transaction createSend(Address address, Coin nanocoins) throws InsufficientMoneyException {
         SendRequest req = SendRequest.to(address, nanocoins);
         if (params == UnitTestParams.get())
             req.shuffleOutputs = false;
@@ -2243,7 +2243,7 @@ public class Wallet extends BaseTaggableObject implements Serializable, BlockCha
      * @return An object containing the transaction that was created, and a future for the broadcast of it.
      * @throws InsufficientMoneyException if the request could not be completed due to not enough balance.
      */
-    public SendResult sendCoins(TransactionBroadcaster broadcaster, Address to, BigInteger value) throws InsufficientMoneyException {
+    public SendResult sendCoins(TransactionBroadcaster broadcaster, Address to, Coin value) throws InsufficientMoneyException {
         SendRequest request = SendRequest.to(to, value);
         return sendCoins(broadcaster, request);
     }
@@ -2335,17 +2335,17 @@ public class Wallet extends BaseTaggableObject implements Serializable, BlockCha
         try {
             checkArgument(!req.completed, "Given SendRequest has already been completed.");
             // Calculate the amount of value we need to import.
-            BigInteger value = BigInteger.ZERO;
+            Coin value = Coin.ZERO;
             for (TransactionOutput output : req.tx.getOutputs()) {
                 value = value.add(output.getValue());
             }
-            BigInteger totalOutput = value;
+            Coin totalOutput = value;
 
             log.info("Completing send tx with {} outputs totalling {} satoshis (not including fees)",
                     req.tx.getOutputs().size(), value);
 
             // If any inputs have already been added, we don't need to get their value from wallet
-            BigInteger totalInput = BigInteger.ZERO;
+            Coin totalInput = Coin.ZERO;
             for (TransactionInput input : req.tx.getInputs())
                 if (input.getConnectedOutput() != null)
                     totalInput = totalInput.add(input.getConnectedOutput().getValue());
@@ -2397,8 +2397,8 @@ public class Wallet extends BaseTaggableObject implements Serializable, BlockCha
                 req.tx.addInput(output);
 
             if (req.ensureMinRequiredFee && req.emptyWallet) {
-                final BigInteger baseFee = req.fee == null ? BigInteger.ZERO : req.fee;
-                final BigInteger feePerKb = req.feePerKb == null ? BigInteger.ZERO : req.feePerKb;
+                final Coin baseFee = req.fee == null ? Coin.ZERO : req.fee;
+                final Coin feePerKb = req.feePerKb == null ? Coin.ZERO : req.feePerKb;
                 Transaction tx = req.tx;
                 if (!adjustOutputDownwardsForFee(tx, bestCoinSelection, baseFee, feePerKb))
                     throw new CouldNotAdjustDownwards();
@@ -2411,7 +2411,7 @@ public class Wallet extends BaseTaggableObject implements Serializable, BlockCha
                 totalOutput = totalOutput.add(bestChangeOutput.getValue());
                 log.info("  with {} coins change", bitcoinValueToFriendlyString(bestChangeOutput.getValue()));
             }
-            final BigInteger calculatedFee = totalInput.subtract(totalOutput);
+            final Coin calculatedFee = totalInput.subtract(totalOutput);
             if (calculatedFee.signum() > 0) {
                 log.info("  with a fee of {}", bitcoinValueToFriendlyString(calculatedFee));
             }
@@ -2445,12 +2445,12 @@ public class Wallet extends BaseTaggableObject implements Serializable, BlockCha
     }
 
     /** Reduce the value of the first output of a transaction to pay the given feePerKb as appropriate for its size. */
-    private boolean adjustOutputDownwardsForFee(Transaction tx, CoinSelection coinSelection, BigInteger baseFee, BigInteger feePerKb) {
+    private boolean adjustOutputDownwardsForFee(Transaction tx, CoinSelection coinSelection, Coin baseFee, Coin feePerKb) {
         TransactionOutput output = tx.getOutput(0);
         // Check if we need additional fee due to the transaction's size
         int size = tx.bitcoinSerialize().length;
         size += estimateBytesForSigning(coinSelection);
-        BigInteger fee = baseFee.add(BigInteger.valueOf((size / 1000) + 1).multiply(feePerKb));
+        Coin fee = baseFee.add(Coin.valueOf((size / 1000) + 1).multiply(feePerKb));
         output.setValue(output.getValue().subtract(fee));
         // Check if we need additional fee due to the output's value
         if (output.getValue().compareTo(Utils.CENT) < 0 && fee.compareTo(Transaction.REFERENCE_DEFAULT_MIN_TX_FEE) < 0)
@@ -2538,21 +2538,21 @@ public class Wallet extends BaseTaggableObject implements Serializable, BlockCha
      * Returns the AVAILABLE balance of this wallet. See {@link BalanceType#AVAILABLE} for details on what this
      * means.
      */
-    public BigInteger getBalance() {
+    public Coin getBalance() {
         return getBalance(BalanceType.AVAILABLE);
     }
 
     /**
      * Returns the balance of this wallet as calculated by the provided balanceType.
      */
-    public BigInteger getBalance(BalanceType balanceType) {
+    public Coin getBalance(BalanceType balanceType) {
         lock.lock();
         try {
             if (balanceType == BalanceType.AVAILABLE) {
                 return getBalance(coinSelector);
             } else if (balanceType == BalanceType.ESTIMATED) {
                 LinkedList<TransactionOutput> all = calculateAllSpendCandidates(false);
-                BigInteger value = BigInteger.ZERO;
+                Coin value = Coin.ZERO;
                 for (TransactionOutput out : all) value = value.add(out.getValue());
                 return value;
             } else {
@@ -2567,7 +2567,7 @@ public class Wallet extends BaseTaggableObject implements Serializable, BlockCha
      * Returns the balance that would be considered spendable by the given coin selector. Just asks it to select
      * as many coins as possible and returns the total.
      */
-    public BigInteger getBalance(CoinSelector selector) {
+    public Coin getBalance(CoinSelector selector) {
         lock.lock();
         try {
             checkNotNull(selector);
@@ -2580,7 +2580,7 @@ public class Wallet extends BaseTaggableObject implements Serializable, BlockCha
     }
 
     /** Returns the available balance, including any unspent balance at watched addresses */
-    public BigInteger getWatchedBalance() {
+    public Coin getWatchedBalance() {
         return getWatchedBalance(coinSelector);
     }
 
@@ -2588,7 +2588,7 @@ public class Wallet extends BaseTaggableObject implements Serializable, BlockCha
      * Returns the balance that would be considered spendable by the given coin selector, including
      * any unspent balance at watched addresses.
      */
-    public BigInteger getWatchedBalance(CoinSelector selector) {
+    public Coin getWatchedBalance(CoinSelector selector) {
         lock.lock();
         try {
             checkNotNull(selector);
@@ -2619,8 +2619,8 @@ public class Wallet extends BaseTaggableObject implements Serializable, BlockCha
         lock.lock();
         try {
             StringBuilder builder = new StringBuilder();
-            BigInteger estimatedBalance = getBalance(BalanceType.ESTIMATED);
-            BigInteger availableBalance = getBalance(BalanceType.AVAILABLE);
+            Coin estimatedBalance = getBalance(BalanceType.ESTIMATED);
+            Coin availableBalance = getBalance(BalanceType.AVAILABLE);
             builder.append(String.format("Wallet containing %s BTC (available: %s BTC) in:%n",
                     bitcoinValueToPlainString(estimatedBalance), bitcoinValueToPlainString(availableBalance)));
             builder.append(String.format("  %d pending transactions%n", pending.size()));
@@ -2861,7 +2861,7 @@ public class Wallet extends BaseTaggableObject implements Serializable, BlockCha
                 notifyNewBestBlock(block);
             }
             checkState(isConsistent());
-            final BigInteger balance = getBalance();
+            final Coin balance = getBalance();
             log.info("post-reorg balance is {}", Utils.bitcoinValueToFriendlyString(balance));
             // Inform event listeners that a re-org took place.
             queueOnReorganize();
@@ -3307,8 +3307,8 @@ public class Wallet extends BaseTaggableObject implements Serializable, BlockCha
     }
 
     private static class BalanceFutureRequest {
-        public SettableFuture<BigInteger> future;
-        public BigInteger value;
+        public SettableFuture<Coin> future;
+        public Coin value;
         public BalanceType type;
     }
     @GuardedBy("lock") private List<BalanceFutureRequest> balanceFutureRequests = Lists.newLinkedList();
@@ -3327,11 +3327,11 @@ public class Wallet extends BaseTaggableObject implements Serializable, BlockCha
      * you can use {@link com.google.bitcoin.utils.Threading#waitForUserCode()} to block until the future had a
      * chance to be updated.</p>
      */
-    public ListenableFuture<BigInteger> getBalanceFuture(final BigInteger value, final BalanceType type) {
+    public ListenableFuture<Coin> getBalanceFuture(final Coin value, final BalanceType type) {
         lock.lock();
         try {
-            final SettableFuture<BigInteger> future = SettableFuture.create();
-            final BigInteger current = getBalance(type);
+            final SettableFuture<Coin> future = SettableFuture.create();
+            final Coin current = getBalance(type);
             if (current.compareTo(value) >= 0) {
                 // Already have enough.
                 future.set(current);
@@ -3352,13 +3352,13 @@ public class Wallet extends BaseTaggableObject implements Serializable, BlockCha
     }
 
     // Runs any balance futures in the user code thread.
-    private void checkBalanceFuturesLocked(@Nullable BigInteger avail) {
+    private void checkBalanceFuturesLocked(@Nullable Coin avail) {
         checkState(lock.isHeldByCurrentThread());
-        BigInteger estimated = null;
+        Coin estimated = null;
         final ListIterator<BalanceFutureRequest> it = balanceFutureRequests.listIterator();
         while (it.hasNext()) {
             final BalanceFutureRequest req = it.next();
-            BigInteger val = null;
+            Coin val = null;
             if (req.type == BalanceType.AVAILABLE) {
                 if (avail == null) avail = getBalance(BalanceType.AVAILABLE);
                 if (avail.compareTo(req.value) < 0) continue;
@@ -3370,7 +3370,7 @@ public class Wallet extends BaseTaggableObject implements Serializable, BlockCha
             }
             // Found one that's finished.
             it.remove();
-            final BigInteger v = checkNotNull(val);
+            final Coin v = checkNotNull(val);
             // Don't run any user-provided future listeners with our lock held.
             Threading.USER_THREAD.execute(new Runnable() {
                 @Override public void run() {
@@ -3483,7 +3483,7 @@ public class Wallet extends BaseTaggableObject implements Serializable, BlockCha
         }
     }
 
-    private void queueOnCoinsReceived(final Transaction tx, final BigInteger balance, final BigInteger newBalance) {
+    private void queueOnCoinsReceived(final Transaction tx, final Coin balance, final Coin newBalance) {
         checkState(lock.isHeldByCurrentThread());
         for (final ListenerRegistration<WalletEventListener> registration : eventListeners) {
             registration.executor.execute(new Runnable() {
@@ -3495,7 +3495,7 @@ public class Wallet extends BaseTaggableObject implements Serializable, BlockCha
         }
     }
 
-    private void queueOnCoinsSent(final Transaction tx, final BigInteger prevBalance, final BigInteger newBalance) {
+    private void queueOnCoinsSent(final Transaction tx, final Coin prevBalance, final Coin newBalance) {
         checkState(lock.isHeldByCurrentThread());
         for (final ListenerRegistration<WalletEventListener> registration : eventListeners) {
             registration.executor.execute(new Runnable() {
@@ -3540,7 +3540,7 @@ public class Wallet extends BaseTaggableObject implements Serializable, BlockCha
         private CoinSelection bestCoinSelection;
         private TransactionOutput bestChangeOutput;
 
-        public FeeCalculation(SendRequest req, BigInteger value, List<TransactionInput> originalInputs,
+        public FeeCalculation(SendRequest req, Coin value, List<TransactionInput> originalInputs,
                               boolean needAtLeastReferenceFee, LinkedList<TransactionOutput> candidates) throws InsufficientMoneyException {
             checkState(lock.isHeldByCurrentThread());
             // There are 3 possibilities for what adding change might do:
@@ -3550,7 +3550,7 @@ public class Wallet extends BaseTaggableObject implements Serializable, BlockCha
             // If we get either of the last 2, we keep note of what the inputs looked like at the time and try to
             // add inputs as we go up the list (keeping track of minimum inputs for each category).  At the end, we pick
             // the best input set as the one which generates the lowest total fee.
-            BigInteger additionalValueForNextCategory = null;
+            Coin additionalValueForNextCategory = null;
             CoinSelection selection3 = null;
             CoinSelection selection2 = null;
             TransactionOutput selection2Change = null;
@@ -3559,14 +3559,14 @@ public class Wallet extends BaseTaggableObject implements Serializable, BlockCha
             // We keep track of the last size of the transaction we calculated but only if the act of adding inputs and
             // change resulted in the size crossing a 1000 byte boundary. Otherwise it stays at zero.
             int lastCalculatedSize = 0;
-            BigInteger valueNeeded, valueMissing = null;
+            Coin valueNeeded, valueMissing = null;
             while (true) {
                 resetTxInputs(req, originalInputs);
 
-                BigInteger fees = req.fee == null ? BigInteger.ZERO : req.fee;
+                Coin fees = req.fee == null ? Coin.ZERO : req.fee;
                 if (lastCalculatedSize > 0) {
                     // If the size is exactly 1000 bytes then we'll over-pay, but this should be rare.
-                    fees = fees.add(BigInteger.valueOf((lastCalculatedSize / 1000) + 1).multiply(req.feePerKb));
+                    fees = fees.add(Coin.valueOf((lastCalculatedSize / 1000) + 1).multiply(req.feePerKb));
                 } else {
                     fees = fees.add(req.feePerKb);  // First time around the loop.
                 }
@@ -3576,7 +3576,7 @@ public class Wallet extends BaseTaggableObject implements Serializable, BlockCha
                 valueNeeded = value.add(fees);
                 if (additionalValueForNextCategory != null)
                     valueNeeded = valueNeeded.add(additionalValueForNextCategory);
-                BigInteger additionalValueSelected = additionalValueForNextCategory;
+                Coin additionalValueSelected = additionalValueForNextCategory;
 
                 // Of the coins we could spend, pick some that we actually will spend.
                 CoinSelector selector = req.coinSelector == null ? coinSelector : req.coinSelector;
@@ -3598,12 +3598,12 @@ public class Wallet extends BaseTaggableObject implements Serializable, BlockCha
                 boolean eitherCategory2Or3 = false;
                 boolean isCategory3 = false;
 
-                BigInteger change = selection.valueGathered.subtract(valueNeeded);
+                Coin change = selection.valueGathered.subtract(valueNeeded);
                 if (additionalValueSelected != null)
                     change = change.add(additionalValueSelected);
 
                 // If change is < 0.01 BTC, we will need to have at least minfee to be accepted by the network
-                if (req.ensureMinRequiredFee && !change.equals(BigInteger.ZERO) &&
+                if (req.ensureMinRequiredFee && !change.equals(Coin.ZERO) &&
                         change.compareTo(Utils.CENT) < 0 && fees.compareTo(Transaction.REFERENCE_DEFAULT_MIN_TX_FEE) < 0) {
                     // This solution may fit into category 2, but it may also be category 3, we'll check that later
                     eitherCategory2Or3 = true;
@@ -3627,7 +3627,7 @@ public class Wallet extends BaseTaggableObject implements Serializable, BlockCha
                         // This solution definitely fits in category 3
                         isCategory3 = true;
                         additionalValueForNextCategory = Transaction.REFERENCE_DEFAULT_MIN_TX_FEE.add(
-                                                         Transaction.MIN_NONDUST_OUTPUT.add(BigInteger.ONE));
+                                                         Transaction.MIN_NONDUST_OUTPUT.add(Coin.ONE));
                     } else {
                         size += changeOutput.bitcoinSerialize().length + VarInt.sizeOf(req.tx.getOutputs().size()) - VarInt.sizeOf(req.tx.getOutputs().size() - 1);
                         // This solution is either category 1 or 2
@@ -3638,7 +3638,7 @@ public class Wallet extends BaseTaggableObject implements Serializable, BlockCha
                     if (eitherCategory2Or3) {
                         // This solution definitely fits in category 3 (we threw away change because it was smaller than MIN_TX_FEE)
                         isCategory3 = true;
-                        additionalValueForNextCategory = Transaction.REFERENCE_DEFAULT_MIN_TX_FEE.add(BigInteger.ONE);
+                        additionalValueForNextCategory = Transaction.REFERENCE_DEFAULT_MIN_TX_FEE.add(Coin.ONE);
                     }
                 }
 
@@ -3694,7 +3694,7 @@ public class Wallet extends BaseTaggableObject implements Serializable, BlockCha
                 throw new InsufficientMoneyException(valueMissing);
             }
 
-            BigInteger lowestFee = null;
+            Coin lowestFee = null;
             bestCoinSelection = null;
             bestChangeOutput = null;
             if (selection1 != null) {
@@ -3707,7 +3707,7 @@ public class Wallet extends BaseTaggableObject implements Serializable, BlockCha
             }
 
             if (selection2 != null) {
-                BigInteger fee = selection2.valueGathered.subtract(checkNotNull(selection2Change).getValue());
+                Coin fee = selection2.valueGathered.subtract(checkNotNull(selection2Change).getValue());
                 if (lowestFee == null || fee.compareTo(lowestFee) < 0) {
                     lowestFee = fee;
                     bestCoinSelection = selection2;
@@ -3896,14 +3896,14 @@ public class Wallet extends BaseTaggableObject implements Serializable, BlockCha
             // bug that was fixed in 0.10, thus, making a re-key transaction depend on those would cause it to
             // never confirm at all.
             CoinSelector selector = new KeyTimeCoinSelector(this, keyRotationTimestamp, true);
-            CoinSelection toMove = selector.select(BigInteger.ZERO, calculateAllSpendCandidates(true));
-            if (toMove.valueGathered.equals(BigInteger.ZERO)) return null;  // Nothing to do.
+            CoinSelection toMove = selector.select(Coin.ZERO, calculateAllSpendCandidates(true));
+            if (toMove.valueGathered.equals(Coin.ZERO)) return null;  // Nothing to do.
             rekeyTx = new Transaction(params);
             for (TransactionOutput output : toMove.gathered) {
                 rekeyTx.addInput(output);
             }
             rekeyTx.addOutput(toMove.valueGathered, safeKey);
-            if (!adjustOutputDownwardsForFee(rekeyTx, toMove, BigInteger.ZERO, Transaction.REFERENCE_DEFAULT_MIN_TX_FEE)) {
+            if (!adjustOutputDownwardsForFee(rekeyTx, toMove, Coin.ZERO, Transaction.REFERENCE_DEFAULT_MIN_TX_FEE)) {
                 log.error("Failed to adjust rekey tx for fees.");
                 return null;
             }
diff --git a/core/src/main/java/com/google/bitcoin/core/WalletEventListener.java b/core/src/main/java/com/google/bitcoin/core/WalletEventListener.java
index ca5e9f76..40d31ea6 100644
--- a/core/src/main/java/com/google/bitcoin/core/WalletEventListener.java
+++ b/core/src/main/java/com/google/bitcoin/core/WalletEventListener.java
@@ -19,7 +19,6 @@ package com.google.bitcoin.core;
 import com.google.bitcoin.script.Script;
 import com.google.bitcoin.wallet.KeyChainEventListener;
 
-import java.math.BigInteger;
 import java.util.List;
 
 /**
@@ -40,7 +39,7 @@ public interface WalletEventListener extends KeyChainEventListener {
      * @param prevBalance Balance before the coins were received.
      * @param newBalance  Current balance of the wallet. This is the 'estimated' balance.
      */
-    void onCoinsReceived(Wallet wallet, Transaction tx, BigInteger prevBalance, BigInteger newBalance);
+    void onCoinsReceived(Wallet wallet, Transaction tx, Coin prevBalance, Coin newBalance);
 
     /**
      * This is called when a transaction is seen that sends coins <b>from</b> this wallet, either
@@ -58,7 +57,7 @@ public interface WalletEventListener extends KeyChainEventListener {
      * @param prevBalance  The wallets balance before this transaction was seen.
      * @param newBalance   The wallets balance after this transaction was seen. This is the 'estimated' balance.
      */
-    void onCoinsSent(Wallet wallet, Transaction tx, BigInteger prevBalance, BigInteger newBalance);
+    void onCoinsSent(Wallet wallet, Transaction tx, Coin prevBalance, Coin newBalance);
 
     // TODO: Finish onReorganize to be more useful.
     /**
diff --git a/core/src/main/java/com/google/bitcoin/jni/NativePaymentChannelServerConnectionEventHandler.java b/core/src/main/java/com/google/bitcoin/jni/NativePaymentChannelServerConnectionEventHandler.java
index c8d5ebd8..82940701 100644
--- a/core/src/main/java/com/google/bitcoin/jni/NativePaymentChannelServerConnectionEventHandler.java
+++ b/core/src/main/java/com/google/bitcoin/jni/NativePaymentChannelServerConnectionEventHandler.java
@@ -4,8 +4,6 @@ import com.google.bitcoin.core.*;
 import com.google.bitcoin.protocols.channels.PaymentChannelCloseException;
 import com.google.bitcoin.protocols.channels.ServerConnectionEventHandler;
 
-import java.math.BigInteger;
-
 /**
  * An event listener that relays events to a native C++ object. A pointer to that object is stored in
  * this class using JNI on the native side, thus several instances of this can point to different actual
@@ -18,7 +16,7 @@ public class NativePaymentChannelServerConnectionEventHandler extends ServerConn
     public native void channelOpen(Sha256Hash channelId);
 
     @Override
-    public native void paymentIncrease(BigInteger by, BigInteger to);
+    public native void paymentIncrease(Coin by, Coin to);
 
     @Override
     public native void channelClosed(PaymentChannelCloseException.CloseReason reason);
diff --git a/core/src/main/java/com/google/bitcoin/jni/NativeWalletEventListener.java b/core/src/main/java/com/google/bitcoin/jni/NativeWalletEventListener.java
index 091f0019..0a324c52 100644
--- a/core/src/main/java/com/google/bitcoin/jni/NativeWalletEventListener.java
+++ b/core/src/main/java/com/google/bitcoin/jni/NativeWalletEventListener.java
@@ -16,13 +16,13 @@
 
 package com.google.bitcoin.jni;
 
+import com.google.bitcoin.core.Coin;
 import com.google.bitcoin.core.ECKey;
 import com.google.bitcoin.core.Transaction;
 import com.google.bitcoin.core.Wallet;
 import com.google.bitcoin.core.WalletEventListener;
 import com.google.bitcoin.script.Script;
 
-import java.math.BigInteger;
 import java.util.List;
 
 /**
@@ -34,10 +34,10 @@ public class NativeWalletEventListener implements WalletEventListener {
     public long ptr;
 
     @Override
-    public native void onCoinsReceived(Wallet wallet, Transaction tx, BigInteger prevBalance, BigInteger newBalance);
+    public native void onCoinsReceived(Wallet wallet, Transaction tx, Coin prevBalance, Coin newBalance);
 
     @Override
-    public native void onCoinsSent(Wallet wallet, Transaction tx, BigInteger prevBalance, BigInteger newBalance);
+    public native void onCoinsSent(Wallet wallet, Transaction tx, Coin prevBalance, Coin newBalance);
 
     @Override
     public native void onReorganize(Wallet wallet);
diff --git a/core/src/main/java/com/google/bitcoin/protocols/channels/IPaymentChannelClient.java b/core/src/main/java/com/google/bitcoin/protocols/channels/IPaymentChannelClient.java
index 0c2e644e..c3b026f4 100644
--- a/core/src/main/java/com/google/bitcoin/protocols/channels/IPaymentChannelClient.java
+++ b/core/src/main/java/com/google/bitcoin/protocols/channels/IPaymentChannelClient.java
@@ -16,11 +16,11 @@
 
 package com.google.bitcoin.protocols.channels;
 
+import com.google.bitcoin.core.Coin;
 import com.google.bitcoin.core.InsufficientMoneyException;
 import com.google.common.util.concurrent.ListenableFuture;
-import org.bitcoin.paymentchannel.Protos;
 
-import java.math.BigInteger;
+import org.bitcoin.paymentchannel.Protos;
 
 /**
  * A class implementing this interface supports the basic operations of a payment channel. An implementation is provided
@@ -80,7 +80,7 @@ public interface IPaymentChannelClient {
      *                               (see {@link PaymentChannelClientConnection#getChannelOpenFuture()} for the second)
      * @return a future that completes when the server acknowledges receipt and acceptance of the payment.
      */
-    ListenableFuture<BigInteger> incrementPayment(BigInteger size) throws ValueOutOfRangeException, IllegalStateException;
+    ListenableFuture<Coin> incrementPayment(Coin size) throws ValueOutOfRangeException, IllegalStateException;
 
     /**
      * Implements the connection between this client and the server, providing an interface which allows messages to be
@@ -118,7 +118,7 @@ public interface IPaymentChannelClient {
 
         /**
          * <p>Indicates the channel has been successfully opened and
-         * {@link com.google.bitcoin.protocols.channels.PaymentChannelClient#incrementPayment(java.math.BigInteger)}
+         * {@link com.google.bitcoin.protocols.channels.PaymentChannelClient#incrementPayment(java.math.Coin)}
          * may be called at will.</p>
          *
          * <p>Called while holding a lock on the {@link com.google.bitcoin.protocols.channels.PaymentChannelClient}
diff --git a/core/src/main/java/com/google/bitcoin/protocols/channels/PaymentChannelClient.java b/core/src/main/java/com/google/bitcoin/protocols/channels/PaymentChannelClient.java
index f9247bc5..199548e6 100644
--- a/core/src/main/java/com/google/bitcoin/protocols/channels/PaymentChannelClient.java
+++ b/core/src/main/java/com/google/bitcoin/protocols/channels/PaymentChannelClient.java
@@ -29,7 +29,6 @@ import org.bitcoin.paymentchannel.Protos;
 import org.slf4j.LoggerFactory;
 
 import javax.annotation.Nullable;
-import java.math.BigInteger;
 import java.util.concurrent.locks.ReentrantLock;
 
 import static com.google.common.base.Preconditions.checkNotNull;
@@ -85,14 +84,14 @@ public class PaymentChannelClient implements IPaymentChannelClient {
 
     // Information used during channel initialization to send to the server or check what the server sends to us
     private final ECKey myKey;
-    private final BigInteger maxValue;
+    private final Coin maxValue;
 
-    private BigInteger missing;
+    private Coin missing;
 
     @GuardedBy("lock") private long minPayment;
 
-    @GuardedBy("lock") SettableFuture<BigInteger> increasePaymentFuture;
-    @GuardedBy("lock") BigInteger lastPaymentActualAmount;
+    @GuardedBy("lock") SettableFuture<Coin> increasePaymentFuture;
+    @GuardedBy("lock") Coin lastPaymentActualAmount;
 
     /**
      * <p>The maximum amount of time for which we will accept the server locking up our funds for the multisig
@@ -122,7 +121,7 @@ public class PaymentChannelClient implements IPaymentChannelClient {
      * @param conn A callback listener which represents the connection to the server (forwards messages we generate to
      *             the server)
      */
-    public PaymentChannelClient(Wallet wallet, ECKey myKey, BigInteger maxValue, Sha256Hash serverId, ClientConnection conn) {
+    public PaymentChannelClient(Wallet wallet, ECKey myKey, Coin maxValue, Sha256Hash serverId, ClientConnection conn) {
         this.wallet = checkNotNull(wallet);
         this.myKey = checkNotNull(myKey);
         this.maxValue = checkNotNull(maxValue);
@@ -136,13 +135,13 @@ public class PaymentChannelClient implements IPaymentChannelClient {
      * <p>When InsufficientMoneyException is thrown due to the server requesting too much value, an instance of 
      * PaymentChannelClient needs access to how many satoshis are missing.</p>
      */
-    public BigInteger getMissing() {
+    public Coin getMissing() {
         return missing;
     }
 
     @Nullable
     @GuardedBy("lock")
-    private CloseReason receiveInitiate(Protos.Initiate initiate, BigInteger contractValue, Protos.Error.Builder errorBuilder) throws VerificationException, InsufficientMoneyException {
+    private CloseReason receiveInitiate(Protos.Initiate initiate, Coin contractValue, Protos.Error.Builder errorBuilder) throws VerificationException, InsufficientMoneyException {
         log.info("Got INITIATE message:\n{}", initiate.toString());
 
         checkState(initiate.getExpireTimeSecs() > 0 && initiate.getMinAcceptedChannelSize() >= 0);
@@ -156,7 +155,7 @@ public class PaymentChannelClient implements IPaymentChannelClient {
             return CloseReason.TIME_WINDOW_TOO_LARGE;
         }
 
-        BigInteger minChannelSize = BigInteger.valueOf(initiate.getMinAcceptedChannelSize());
+        Coin minChannelSize = Coin.valueOf(initiate.getMinAcceptedChannelSize());
         if (contractValue.compareTo(minChannelSize) < 0) {
             log.error("Server requested too much value");
             errorBuilder.setCode(Protos.Error.ErrorCode.CHANNEL_VALUE_TOO_LARGE);
@@ -171,7 +170,7 @@ public class PaymentChannelClient implements IPaymentChannelClient {
             log.error("Server requested a min payment of {} but we expected {}", initiate.getMinPayment(), MIN_PAYMENT);
             errorBuilder.setCode(Protos.Error.ErrorCode.MIN_PAYMENT_TOO_LARGE);
             errorBuilder.setExpectedValue(MIN_PAYMENT);
-            missing = BigInteger.valueOf(initiate.getMinPayment() - MIN_PAYMENT);
+            missing = Coin.valueOf(initiate.getMinPayment() - MIN_PAYMENT);
             return CloseReason.SERVER_REQUESTED_TOO_MUCH_VALUE;
         }
 
@@ -218,7 +217,7 @@ public class PaymentChannelClient implements IPaymentChannelClient {
         try {
             // Make an initial payment of the dust limit, and put it into the message as well. The size of the
             // server-requested dust limit was already sanity checked by this point.
-            PaymentChannelClientState.IncrementedPayment payment = state().incrementPaymentBy(BigInteger.valueOf(minPayment));
+            PaymentChannelClientState.IncrementedPayment payment = state().incrementPaymentBy(Coin.valueOf(minPayment));
             Protos.UpdatePayment.Builder initialMsg = contractMsg.getInitialPaymentBuilder();
             initialMsg.setSignature(ByteString.copyFrom(payment.signature.encodeToBitcoin()));
             initialMsg.setClientChangeValue(state.getValueRefunded().longValue());
@@ -470,7 +469,7 @@ public class PaymentChannelClient implements IPaymentChannelClient {
      * @return a future that completes when the server acknowledges receipt and acceptance of the payment.
      */
     @Override
-    public ListenableFuture<BigInteger> incrementPayment(BigInteger size) throws ValueOutOfRangeException, IllegalStateException {
+    public ListenableFuture<Coin> incrementPayment(Coin size) throws ValueOutOfRangeException, IllegalStateException {
         lock.lock();
         try {
             if (state() == null || !connectionOpen || step != InitStep.CHANNEL_OPEN)
@@ -505,8 +504,8 @@ public class PaymentChannelClient implements IPaymentChannelClient {
     }
 
     private void receivePaymentAck() {
-        SettableFuture<BigInteger> future;
-        BigInteger value;
+        SettableFuture<Coin> future;
+        Coin value;
 
         lock.lock();
         try {
diff --git a/core/src/main/java/com/google/bitcoin/protocols/channels/PaymentChannelClientConnection.java b/core/src/main/java/com/google/bitcoin/protocols/channels/PaymentChannelClientConnection.java
index c8aacebd..92ea7d56 100644
--- a/core/src/main/java/com/google/bitcoin/protocols/channels/PaymentChannelClientConnection.java
+++ b/core/src/main/java/com/google/bitcoin/protocols/channels/PaymentChannelClientConnection.java
@@ -16,6 +16,7 @@
 
 package com.google.bitcoin.protocols.channels;
 
+import com.google.bitcoin.core.Coin;
 import com.google.bitcoin.core.ECKey;
 import com.google.bitcoin.core.InsufficientMoneyException;
 import com.google.bitcoin.core.Sha256Hash;
@@ -24,10 +25,10 @@ import com.google.bitcoin.net.NioClient;
 import com.google.bitcoin.net.ProtobufParser;
 import com.google.common.util.concurrent.ListenableFuture;
 import com.google.common.util.concurrent.SettableFuture;
+
 import org.bitcoin.paymentchannel.Protos;
 
 import java.io.IOException;
-import java.math.BigInteger;
 import java.net.InetSocketAddress;
 
 /**
@@ -60,7 +61,7 @@ public class PaymentChannelClientConnection {
      * @throws ValueOutOfRangeException if the balance of wallet is lower than maxValue.
      */
     public PaymentChannelClientConnection(InetSocketAddress server, int timeoutSeconds, Wallet wallet, ECKey myKey,
-                                          BigInteger maxValue, String serverId) throws IOException, ValueOutOfRangeException {
+                                          Coin maxValue, String serverId) throws IOException, ValueOutOfRangeException {
         // Glue the object which vends/ingests protobuf messages in order to manage state to the network object which
         // reads/writes them to the wire in length prefixed form.
         channelClient = new PaymentChannelClient(wallet, myKey, maxValue, Sha256Hash.create(serverId.getBytes()),
@@ -119,7 +120,7 @@ public class PaymentChannelClientConnection {
      * an error before the channel has reached the open state.</p>
      *
      * <p>After this future completes successfully, you may call
-     * {@link PaymentChannelClientConnection#incrementPayment(java.math.BigInteger)} to begin paying the server.</p>
+     * {@link PaymentChannelClientConnection#incrementPayment(java.math.Coin)} to begin paying the server.</p>
      */
     public ListenableFuture<PaymentChannelClientConnection> getChannelOpenFuture() {
         return channelOpenFuture;
@@ -134,7 +135,7 @@ public class PaymentChannelClientConnection {
      * @throws IllegalStateException If the channel has been closed or is not yet open
      *                               (see {@link PaymentChannelClientConnection#getChannelOpenFuture()} for the second)
      */
-    public ListenableFuture<BigInteger> incrementPayment(BigInteger size) throws ValueOutOfRangeException, IllegalStateException {
+    public ListenableFuture<Coin> incrementPayment(Coin size) throws ValueOutOfRangeException, IllegalStateException {
         return channelClient.incrementPayment(size);
     }
 
diff --git a/core/src/main/java/com/google/bitcoin/protocols/channels/PaymentChannelClientState.java b/core/src/main/java/com/google/bitcoin/protocols/channels/PaymentChannelClientState.java
index 1893ec4e..4f7826cb 100644
--- a/core/src/main/java/com/google/bitcoin/protocols/channels/PaymentChannelClientState.java
+++ b/core/src/main/java/com/google/bitcoin/protocols/channels/PaymentChannelClientState.java
@@ -31,7 +31,6 @@ import com.google.common.util.concurrent.ListenableFuture;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
-import java.math.BigInteger;
 import java.util.List;
 
 import static com.google.common.base.Preconditions.*;
@@ -75,20 +74,20 @@ public class PaymentChannelClientState {
     // and transactions that spend it.
     private final ECKey myKey, serverMultisigKey;
     // How much value (in satoshis) is locked up into the channel.
-    private final BigInteger totalValue;
+    private final Coin totalValue;
     // When the channel will automatically settle in favor of the client, if the server halts before protocol termination
     // specified in terms of block timestamps (so it can off real time by a few hours).
     private final long expiryTime;
 
     // The refund is a time locked transaction that spends all the money of the channel back to the client.
     private Transaction refundTx;
-    private BigInteger refundFees;
+    private Coin refundFees;
     // The multi-sig contract locks the value of the channel up such that the agreement of both parties is required
     // to spend it.
     private Transaction multisigContract;
     private Script multisigScript;
     // How much value is currently allocated to us. Starts as being same as totalValue.
-    private BigInteger valueToMe;
+    private Coin valueToMe;
 
     /**
      * The different logical states the channel can be in. The channel starts out as NEW, and then steps through the
@@ -156,7 +155,7 @@ public class PaymentChannelClientState {
      * @throws VerificationException If either myKey's pubkey or serverMultisigKey's pubkey are non-canonical (ie invalid)
      */
     public PaymentChannelClientState(Wallet wallet, ECKey myKey, ECKey serverMultisigKey,
-                                     BigInteger value, long expiryTimeInSeconds) throws VerificationException {
+                                     Coin value, long expiryTimeInSeconds) throws VerificationException {
         checkArgument(value.signum() > 0);
         this.wallet = checkNotNull(wallet);
         initWalletListeners();
@@ -174,7 +173,7 @@ public class PaymentChannelClientState {
         }
         wallet.addEventListener(new AbstractWalletEventListener() {
             @Override
-            public void onCoinsReceived(Wallet wallet, Transaction tx, BigInteger prevBalance, BigInteger newBalance) {
+            public void onCoinsReceived(Wallet wallet, Transaction tx, Coin prevBalance, Coin newBalance) {
                 synchronized (PaymentChannelClientState.this) {
                     if (multisigContract == null) return;
                     if (isSettlementTransaction(tx)) {
@@ -253,7 +252,7 @@ public class PaymentChannelClientState {
         editContractSendRequest(req);
         req.shuffleOutputs = false;   // TODO: Fix things so shuffling is usable.
         wallet.completeTx(req);
-        BigInteger multisigFee = req.fee;
+        Coin multisigFee = req.fee;
         multisigContract = req.tx;
         // Build a refund transaction that protects us in the case of a bad server that's just trying to cause havoc
         // by locking up peoples money (perhaps as a precursor to a ransom attempt). We time lock it so the server
@@ -266,7 +265,7 @@ public class PaymentChannelClientState {
         refundTx.setLockTime(expiryTime);
         if (totalValue.compareTo(Utils.CENT) < 0) {
             // Must pay min fee.
-            final BigInteger valueAfterFee = totalValue.subtract(Transaction.REFERENCE_DEFAULT_MIN_TX_FEE);
+            final Coin valueAfterFee = totalValue.subtract(Transaction.REFERENCE_DEFAULT_MIN_TX_FEE);
             if (Transaction.MIN_NONDUST_OUTPUT.compareTo(valueAfterFee) > 0)
                 throw new ValueOutOfRangeException("totalValue too small to use");
             refundTx.addOutput(valueAfterFee, myKey.toAddress(params));
@@ -292,7 +291,7 @@ public class PaymentChannelClientState {
 
     /**
      * Returns the transaction that locks the money to the agreement of both parties. Do not mutate the result.
-     * Once this step is done, you can use {@link PaymentChannelClientState#incrementPaymentBy(java.math.BigInteger)} to
+     * Once this step is done, you can use {@link PaymentChannelClientState#incrementPaymentBy(java.math.Coin)} to
      * start paying the server.
      */
     public synchronized Transaction getMultisigContract() {
@@ -348,7 +347,7 @@ public class PaymentChannelClientState {
         state = State.SAVE_STATE_IN_WALLET;
     }
 
-    private synchronized Transaction makeUnsignedChannelContract(BigInteger valueToMe) throws ValueOutOfRangeException {
+    private synchronized Transaction makeUnsignedChannelContract(Coin valueToMe) throws ValueOutOfRangeException {
         Transaction tx = new Transaction(wallet.getParams());
         tx.addInput(multisigContract.getOutput(0));
         // Our output always comes first.
@@ -373,7 +372,7 @@ public class PaymentChannelClientState {
     /** Container for a signature and an amount that was sent. */
     public static class IncrementedPayment {
         public TransactionSignature signature;
-        public BigInteger amount;
+        public Coin amount;
     }
 
     /**
@@ -391,17 +390,17 @@ public class PaymentChannelClientState {
      * @throws ValueOutOfRangeException If size is negative or the channel does not have sufficient money in it to
      *                                  complete this payment.
      */
-    public synchronized IncrementedPayment incrementPaymentBy(BigInteger size) throws ValueOutOfRangeException {
+    public synchronized IncrementedPayment incrementPaymentBy(Coin size) throws ValueOutOfRangeException {
         checkState(state == State.READY);
         checkNotExpired();
         checkNotNull(size);  // Validity of size will be checked by makeUnsignedChannelContract.
         if (size.signum() < 0)
             throw new ValueOutOfRangeException("Tried to decrement payment");
-        BigInteger newValueToMe = valueToMe.subtract(size);
+        Coin newValueToMe = valueToMe.subtract(size);
         if (newValueToMe.compareTo(Transaction.MIN_NONDUST_OUTPUT) < 0 && newValueToMe.signum() > 0) {
             log.info("New value being sent back as change was smaller than minimum nondust output, sending all");
             size = valueToMe;
-            newValueToMe = BigInteger.ZERO;
+            newValueToMe = Coin.ZERO;
         }
         if (newValueToMe.signum() < 0)
             throw new ValueOutOfRangeException("Channel has too little money to pay " + size + " satoshis");
@@ -410,7 +409,7 @@ public class PaymentChannelClientState {
         Transaction.SigHash mode;
         // If we spent all the money we put into this channel, we (by definition) don't care what the outputs are, so
         // we sign with SIGHASH_NONE to let the server do what it wants.
-        if (newValueToMe.equals(BigInteger.ZERO))
+        if (newValueToMe.equals(Coin.ZERO))
             mode = Transaction.SigHash.NONE;
         else
             mode = Transaction.SigHash.SINGLE;
@@ -500,7 +499,7 @@ public class PaymentChannelClientState {
      * Returns the fees that will be paid if the refund transaction has to be claimed because the server failed to settle
      * the channel properly. May only be called after {@link PaymentChannelClientState#initiate()}
      */
-    public synchronized BigInteger getRefundTxFees() {
+    public synchronized Coin getRefundTxFees() {
         checkState(state.compareTo(State.NEW) > 0);
         return refundFees;
     }
@@ -518,14 +517,14 @@ public class PaymentChannelClientState {
     /**
      * Gets the total value of this channel (ie the maximum payment possible)
      */
-    public BigInteger getTotalValue() {
+    public Coin getTotalValue() {
         return totalValue;
     }
 
     /**
      * Gets the current amount refunded to us from the multisig contract (ie totalValue-valueSentToServer)
      */
-    public synchronized BigInteger getValueRefunded() {
+    public synchronized Coin getValueRefunded() {
         checkState(state == State.READY);
         return valueToMe;
     }
@@ -533,7 +532,7 @@ public class PaymentChannelClientState {
     /**
      * Returns the amount of money sent on this channel so far.
      */
-    public synchronized BigInteger getValueSpent() {
+    public synchronized Coin getValueSpent() {
         return getTotalValue().subtract(getValueRefunded());
     }
 }
diff --git a/core/src/main/java/com/google/bitcoin/protocols/channels/PaymentChannelServer.java b/core/src/main/java/com/google/bitcoin/protocols/channels/PaymentChannelServer.java
index e437465c..dccefe2b 100644
--- a/core/src/main/java/com/google/bitcoin/protocols/channels/PaymentChannelServer.java
+++ b/core/src/main/java/com/google/bitcoin/protocols/channels/PaymentChannelServer.java
@@ -27,7 +27,6 @@ import org.bitcoin.paymentchannel.Protos;
 import org.slf4j.LoggerFactory;
 
 import javax.annotation.Nullable;
-import java.math.BigInteger;
 import java.util.concurrent.locks.ReentrantLock;
 
 import static com.google.common.base.Preconditions.checkNotNull;
@@ -102,7 +101,7 @@ public class PaymentChannelServer {
          * @param by The increase in total payment
          * @param to The new total payment to us (not including fees which may be required to claim the payment)
          */
-        public void paymentIncrease(BigInteger by, BigInteger to);
+        public void paymentIncrease(Coin by, Coin to);
     }
     private final ServerConnection conn;
 
@@ -119,7 +118,7 @@ public class PaymentChannelServer {
     @GuardedBy("lock") private ECKey myKey;
 
     // The minimum accepted channel value
-    private final BigInteger minAcceptedChannelSize;
+    private final Coin minAcceptedChannelSize;
 
     // The state manager for this channel
     @GuardedBy("lock") private PaymentChannelServerState state;
@@ -151,7 +150,7 @@ public class PaymentChannelServer {
      *             the client and will close the connection on request)
      */
     public PaymentChannelServer(TransactionBroadcaster broadcaster, Wallet wallet,
-                                BigInteger minAcceptedChannelSize, ServerConnection conn) {
+                                Coin minAcceptedChannelSize, ServerConnection conn) {
         this.broadcaster = checkNotNull(broadcaster);
         this.wallet = checkNotNull(wallet);
         this.minAcceptedChannelSize = checkNotNull(minAcceptedChannelSize);
@@ -310,10 +309,10 @@ public class PaymentChannelServer {
     private void receiveUpdatePaymentMessage(Protos.UpdatePayment msg, boolean sendAck) throws VerificationException, ValueOutOfRangeException, InsufficientMoneyException {
         log.info("Got a payment update");
 
-        BigInteger lastBestPayment = state.getBestValueToMe();
-        final BigInteger refundSize = BigInteger.valueOf(msg.getClientChangeValue());
+        Coin lastBestPayment = state.getBestValueToMe();
+        final Coin refundSize = Coin.valueOf(msg.getClientChangeValue());
         boolean stillUsable = state.incrementPayment(refundSize, msg.getSignature().toByteArray());
-        BigInteger bestPaymentChange = state.getBestValueToMe().subtract(lastBestPayment);
+        Coin bestPaymentChange = state.getBestValueToMe().subtract(lastBestPayment);
 
         if (bestPaymentChange.signum() > 0)
             conn.paymentIncrease(bestPaymentChange, state.getBestValueToMe());
diff --git a/core/src/main/java/com/google/bitcoin/protocols/channels/PaymentChannelServerListener.java b/core/src/main/java/com/google/bitcoin/protocols/channels/PaymentChannelServerListener.java
index d4ed47fd..d6bb3693 100644
--- a/core/src/main/java/com/google/bitcoin/protocols/channels/PaymentChannelServerListener.java
+++ b/core/src/main/java/com/google/bitcoin/protocols/channels/PaymentChannelServerListener.java
@@ -17,17 +17,19 @@
 
 package com.google.bitcoin.protocols.channels;
 
+import com.google.bitcoin.core.Coin;
 import com.google.bitcoin.core.Sha256Hash;
 import com.google.bitcoin.core.TransactionBroadcaster;
 import com.google.bitcoin.core.Wallet;
 import com.google.bitcoin.net.NioServer;
 import com.google.bitcoin.net.ProtobufParser;
 import com.google.bitcoin.net.StreamParserFactory;
+
 import org.bitcoin.paymentchannel.Protos;
 
 import javax.annotation.Nullable;
+
 import java.io.IOException;
-import java.math.BigInteger;
 import java.net.InetAddress;
 import java.net.InetSocketAddress;
 import java.net.SocketAddress;
@@ -46,7 +48,7 @@ public class PaymentChannelServerListener {
 
     // The event handler factory which creates new ServerConnectionEventHandler per connection
     private final HandlerFactory eventHandlerFactory;
-    private final BigInteger minAcceptedChannelSize;
+    private final Coin minAcceptedChannelSize;
 
     private NioServer server;
     private final int timeoutSeconds;
@@ -80,7 +82,7 @@ public class PaymentChannelServerListener {
                     eventHandler.channelOpen(contractHash);
                 }
 
-                @Override public void paymentIncrease(BigInteger by, BigInteger to) {
+                @Override public void paymentIncrease(Coin by, Coin to) {
                     eventHandler.paymentIncrease(by, to);
                 }
             });
@@ -161,7 +163,7 @@ public class PaymentChannelServerListener {
      * @param eventHandlerFactory A factory which generates event handlers which are created for each new connection
      */
     public PaymentChannelServerListener(TransactionBroadcaster broadcaster, Wallet wallet,
-                                        final int timeoutSeconds, BigInteger minAcceptedChannelSize,
+                                        final int timeoutSeconds, Coin minAcceptedChannelSize,
                                         HandlerFactory eventHandlerFactory) throws IOException {
         this.wallet = checkNotNull(wallet);
         this.broadcaster = checkNotNull(broadcaster);
diff --git a/core/src/main/java/com/google/bitcoin/protocols/channels/PaymentChannelServerState.java b/core/src/main/java/com/google/bitcoin/protocols/channels/PaymentChannelServerState.java
index 69ec3666..c4831d52 100644
--- a/core/src/main/java/com/google/bitcoin/protocols/channels/PaymentChannelServerState.java
+++ b/core/src/main/java/com/google/bitcoin/protocols/channels/PaymentChannelServerState.java
@@ -30,7 +30,6 @@ import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
 import javax.annotation.Nullable;
-import java.math.BigInteger;
 import java.util.Arrays;
 
 import static com.google.common.base.Preconditions.*;
@@ -101,9 +100,9 @@ public class PaymentChannelServerState {
     private byte[] bestValueSignature;
 
     // The total value locked into the multi-sig output and the value to us in the last signature the client provided
-    private BigInteger totalValue;
-    private BigInteger bestValueToMe = BigInteger.ZERO;
-    private BigInteger feePaidForPayment;
+    private Coin totalValue;
+    private Coin bestValueToMe = Coin.ZERO;
+    private Coin feePaidForPayment;
 
     // The refund/change transaction output that goes back to the client
     private TransactionOutput clientOutput;
@@ -126,7 +125,7 @@ public class PaymentChannelServerState {
             this.totalValue = multisigContract.getOutput(0).getValue();
             this.bestValueToMe = checkNotNull(storedServerChannel.bestValueToMe);
             this.bestValueSignature = storedServerChannel.bestValueSignature;
-            checkArgument(bestValueToMe.equals(BigInteger.ZERO) || bestValueSignature != null);
+            checkArgument(bestValueToMe.equals(Coin.ZERO) || bestValueSignature != null);
             this.storedServerChannel = storedServerChannel;
             storedServerChannel.state = this;
             this.state = State.READY;
@@ -263,9 +262,9 @@ public class PaymentChannelServerState {
     }
 
     // Create a payment transaction with valueToMe going back to us
-    private synchronized Wallet.SendRequest makeUnsignedChannelContract(BigInteger valueToMe) {
+    private synchronized Wallet.SendRequest makeUnsignedChannelContract(Coin valueToMe) {
         Transaction tx = new Transaction(wallet.getParams());
-        if (!totalValue.subtract(valueToMe).equals(BigInteger.ZERO)) {
+        if (!totalValue.subtract(valueToMe).equals(Coin.ZERO)) {
             clientOutput.setValue(totalValue.subtract(valueToMe));
             tx.addOutput(clientOutput);
         }
@@ -283,17 +282,17 @@ public class PaymentChannelServerState {
      * @throws VerificationException If the signature does not verify or size is out of range (incl being rejected by the network as dust).
      * @return true if there is more value left on the channel, false if it is now fully used up.
      */
-    public synchronized boolean incrementPayment(BigInteger refundSize, byte[] signatureBytes) throws VerificationException, ValueOutOfRangeException, InsufficientMoneyException {
+    public synchronized boolean incrementPayment(Coin refundSize, byte[] signatureBytes) throws VerificationException, ValueOutOfRangeException, InsufficientMoneyException {
         checkState(state == State.READY);
         checkNotNull(refundSize);
         checkNotNull(signatureBytes);
         TransactionSignature signature = TransactionSignature.decodeFromBitcoin(signatureBytes, true);
         // We allow snapping to zero for the payment amount because it's treated specially later, but not less than
         // the dust level because that would prevent the transaction from being relayed/mined.
-        final boolean fullyUsedUp = refundSize.equals(BigInteger.ZERO);
+        final boolean fullyUsedUp = refundSize.equals(Coin.ZERO);
         if (refundSize.compareTo(clientOutput.getMinNonDustValue()) < 0 && !fullyUsedUp)
             throw new ValueOutOfRangeException("Attempt to refund negative value or value too small to be accepted by the network");
-        BigInteger newValueToMe = totalValue.subtract(refundSize);
+        Coin newValueToMe = totalValue.subtract(refundSize);
         if (newValueToMe.signum() < 0)
             throw new ValueOutOfRangeException("Attempt to refund more than the contract allows.");
         if (newValueToMe.compareTo(bestValueToMe) < 0)
@@ -439,14 +438,14 @@ public class PaymentChannelServerState {
     /**
      * Gets the highest payment to ourselves (which we will receive on settle(), not including fees)
      */
-    public synchronized BigInteger getBestValueToMe() {
+    public synchronized Coin getBestValueToMe() {
         return bestValueToMe;
     }
 
     /**
      * Gets the fee paid in the final payment transaction (only available if settle() did not throw an exception)
      */
-    public synchronized BigInteger getFeePaid() {
+    public synchronized Coin getFeePaid() {
         checkState(state == State.CLOSED || state == State.CLOSING);
         return feePaidForPayment;
     }
diff --git a/core/src/main/java/com/google/bitcoin/protocols/channels/ServerConnectionEventHandler.java b/core/src/main/java/com/google/bitcoin/protocols/channels/ServerConnectionEventHandler.java
index bd4c159d..b9124c61 100644
--- a/core/src/main/java/com/google/bitcoin/protocols/channels/ServerConnectionEventHandler.java
+++ b/core/src/main/java/com/google/bitcoin/protocols/channels/ServerConnectionEventHandler.java
@@ -16,10 +16,10 @@
 
 package com.google.bitcoin.protocols.channels;
 
-import java.math.BigInteger;
-
+import com.google.bitcoin.core.Coin;
 import com.google.bitcoin.core.Sha256Hash;
 import com.google.bitcoin.net.ProtobufParser;
+
 import org.bitcoin.paymentchannel.Protos;
 
 import javax.annotation.Nullable;
@@ -70,7 +70,7 @@ public abstract class ServerConnectionEventHandler {
      * @param by The increase in total payment
      * @param to The new total payment to us (not including fees which may be required to claim the payment)
      */
-    public abstract void paymentIncrease(BigInteger by, BigInteger to);
+    public abstract void paymentIncrease(Coin by, Coin to);
 
     /**
      * <p>Called when the channel was closed for some reason. May be called without a call to
diff --git a/core/src/main/java/com/google/bitcoin/protocols/channels/StoredPaymentChannelClientStates.java b/core/src/main/java/com/google/bitcoin/protocols/channels/StoredPaymentChannelClientStates.java
index e4638848..267d0a4f 100644
--- a/core/src/main/java/com/google/bitcoin/protocols/channels/StoredPaymentChannelClientStates.java
+++ b/core/src/main/java/com/google/bitcoin/protocols/channels/StoredPaymentChannelClientStates.java
@@ -26,7 +26,6 @@ import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
 import javax.annotation.Nullable;
-import java.math.BigInteger;
 import java.util.Date;
 import java.util.Set;
 import java.util.Timer;
@@ -69,8 +68,8 @@ public class StoredPaymentChannelClientStates implements WalletExtension {
     }
 
     /** Returns the outstanding amount of money sent back to us for all channels to this server added together. */
-    public BigInteger getBalanceForServer(Sha256Hash id) {
-        BigInteger balance = BigInteger.ZERO;
+    public Coin getBalanceForServer(Sha256Hash id) {
+        Coin balance = Coin.ZERO;
         lock.lock();
         try {
             Set<StoredClientChannel> setChannels = mapChannels.get(id);
@@ -120,7 +119,7 @@ public class StoredPaymentChannelClientStates implements WalletExtension {
                 synchronized (channel) {
                     // Check if the channel is usable (has money, inactive) and if so, activate it.
                     log.info("Considering channel {} contract {}", channel.hashCode(), channel.contract.getHash());
-                    if (channel.close != null || channel.valueToMe.equals(BigInteger.ZERO)) {
+                    if (channel.close != null || channel.valueToMe.equals(Coin.ZERO)) {
                         log.info("  ... but is closed or empty");
                         continue;
                     }
@@ -256,8 +255,8 @@ public class StoredPaymentChannelClientStates implements WalletExtension {
                         new Transaction(params, storedState.getContractTransaction().toByteArray()),
                         refundTransaction,
                         ECKey.fromPrivate(storedState.getMyKey().toByteArray()),
-                        BigInteger.valueOf(storedState.getValueToMe()),
-                        BigInteger.valueOf(storedState.getRefundFees()), false);
+                        Coin.valueOf(storedState.getValueToMe()),
+                        Coin.valueOf(storedState.getRefundFees()), false);
                 if (storedState.hasCloseTransactionHash())
                     channel.close = containingWallet.getTransaction(new Sha256Hash(storedState.toByteArray()));
                 putChannel(channel, false);
@@ -292,13 +291,13 @@ class StoredClientChannel {
     // The transaction that closed the channel (generated by the server)
     Transaction close;
     ECKey myKey;
-    BigInteger valueToMe, refundFees;
+    Coin valueToMe, refundFees;
 
     // In-memory flag to indicate intent to resume this channel (or that the channel is already in use)
     boolean active = false;
 
-    StoredClientChannel(Sha256Hash id, Transaction contract, Transaction refund, ECKey myKey, BigInteger valueToMe,
-                        BigInteger refundFees, boolean active) {
+    StoredClientChannel(Sha256Hash id, Transaction contract, Transaction refund, ECKey myKey, Coin valueToMe,
+                        Coin refundFees, boolean active) {
         this.id = id;
         this.contract = contract;
         this.refund = refund;
diff --git a/core/src/main/java/com/google/bitcoin/protocols/channels/StoredPaymentChannelServerStates.java b/core/src/main/java/com/google/bitcoin/protocols/channels/StoredPaymentChannelServerStates.java
index b122a40b..4b044586 100644
--- a/core/src/main/java/com/google/bitcoin/protocols/channels/StoredPaymentChannelServerStates.java
+++ b/core/src/main/java/com/google/bitcoin/protocols/channels/StoredPaymentChannelServerStates.java
@@ -24,7 +24,6 @@ import net.jcip.annotations.GuardedBy;
 import org.slf4j.LoggerFactory;
 
 import javax.annotation.Nullable;
-import java.math.BigInteger;
 import java.util.*;
 import java.util.concurrent.locks.ReentrantLock;
 
@@ -183,7 +182,7 @@ public class StoredPaymentChannelServerStates implements WalletExtension {
                         new TransactionOutput(params, null, storedState.getClientOutput().toByteArray(), 0),
                         storedState.getRefundTransactionUnlockTimeSecs(),
                         ECKey.fromPrivate(storedState.getMyKey().toByteArray()),
-                        BigInteger.valueOf(storedState.getBestValueToMe()),
+                        Coin.valueOf(storedState.getBestValueToMe()),
                         storedState.hasBestValueSignature() ? storedState.getBestValueSignature().toByteArray() : null);
                 putChannel(channel);
             }
diff --git a/core/src/main/java/com/google/bitcoin/protocols/channels/StoredServerChannel.java b/core/src/main/java/com/google/bitcoin/protocols/channels/StoredServerChannel.java
index 9dad7952..430fef59 100644
--- a/core/src/main/java/com/google/bitcoin/protocols/channels/StoredServerChannel.java
+++ b/core/src/main/java/com/google/bitcoin/protocols/channels/StoredServerChannel.java
@@ -19,7 +19,6 @@ package com.google.bitcoin.protocols.channels;
 import com.google.bitcoin.core.*;
 
 import javax.annotation.Nullable;
-import java.math.BigInteger;
 import java.util.Date;
 
 import static com.google.common.base.Preconditions.checkArgument;
@@ -30,7 +29,7 @@ import static com.google.common.base.Preconditions.checkArgument;
  * time approaches.
  */
 public class StoredServerChannel {
-    BigInteger bestValueToMe;
+    Coin bestValueToMe;
     byte[] bestValueSignature;
     long refundTransactionUnlockTimeSecs;
     Transaction contract;
@@ -43,7 +42,7 @@ public class StoredServerChannel {
     PaymentChannelServerState state = null;
 
     StoredServerChannel(@Nullable PaymentChannelServerState state, Transaction contract, TransactionOutput clientOutput,
-                        long refundTransactionUnlockTimeSecs, ECKey myKey, BigInteger bestValueToMe, @Nullable byte[] bestValueSignature) {
+                        long refundTransactionUnlockTimeSecs, ECKey myKey, Coin bestValueToMe, @Nullable byte[] bestValueSignature) {
         this.contract = contract;
         this.clientOutput = clientOutput;
         this.refundTransactionUnlockTimeSecs = refundTransactionUnlockTimeSecs;
@@ -57,7 +56,7 @@ public class StoredServerChannel {
      * <p>Updates the best value to the server to the given newValue and newSignature without any checking.</p>
      * <p>Does <i>NOT</i> notify the wallet of an update to the {@link StoredPaymentChannelServerStates}.</p>
      */
-    synchronized void updateValueToMe(BigInteger newValue, byte[] newSignature) {
+    synchronized void updateValueToMe(Coin newValue, byte[] newSignature) {
         this.bestValueToMe = newValue;
         this.bestValueSignature = newSignature;
     }
@@ -107,11 +106,11 @@ public class StoredServerChannel {
         final String newline = String.format("%n");
         return String.format("Stored server channel (%s)%n" +
                 "    Key:           %s%n" +
-                "    Value to me:   %d%n" +
+                "    Value to me:   %s%n" +
                 "    Client output: %s%n" +
                 "    Refund unlock: %s (%d unix time)%n" +
                 "    Contract:    %s%n",
-                connectedHandler != null ? "connected" : "disconnected", myKey, bestValueToMe,
+                connectedHandler != null ? "connected" : "disconnected", myKey, bestValueToMe.toString(),
                 clientOutput,  new Date(refundTransactionUnlockTimeSecs * 1000), refundTransactionUnlockTimeSecs,
                 contract.toString().replaceAll(newline, newline + "    "));
     }
diff --git a/core/src/main/java/com/google/bitcoin/protocols/payments/PaymentProtocol.java b/core/src/main/java/com/google/bitcoin/protocols/payments/PaymentProtocol.java
index 541ca706..009ce012 100644
--- a/core/src/main/java/com/google/bitcoin/protocols/payments/PaymentProtocol.java
+++ b/core/src/main/java/com/google/bitcoin/protocols/payments/PaymentProtocol.java
@@ -18,6 +18,7 @@
 package com.google.bitcoin.protocols.payments;
 
 import com.google.bitcoin.core.Address;
+import com.google.bitcoin.core.Coin;
 import com.google.bitcoin.core.NetworkParameters;
 import com.google.bitcoin.core.Transaction;
 import com.google.bitcoin.crypto.X509Utils;
@@ -30,7 +31,6 @@ import org.bitcoin.protocols.payments.Protos;
 
 import javax.annotation.Nullable;
 import java.io.Serializable;
-import java.math.BigInteger;
 import java.security.*;
 import java.security.cert.*;
 import java.security.cert.Certificate;
@@ -67,7 +67,7 @@ public class PaymentProtocol {
      * @return created payment request, in its builder form
      */
     public static Protos.PaymentRequest.Builder createPaymentRequest(NetworkParameters params,
-            @Nullable BigInteger amount, Address toAddress, @Nullable String memo, @Nullable String paymentUrl,
+            @Nullable Coin amount, Address toAddress, @Nullable String memo, @Nullable String paymentUrl,
             @Nullable byte[] merchantData) {
         return createPaymentRequest(params, ImmutableList.of(createPayToAddressOutput(amount, toAddress)), memo,
                 paymentUrl, merchantData);
@@ -282,7 +282,7 @@ public class PaymentProtocol {
      * @return created payment message
      */
     public static Protos.Payment createPaymentMessage(List<Transaction> transactions,
-            @Nullable BigInteger refundAmount, @Nullable Address refundAddress, @Nullable String memo,
+            @Nullable Coin refundAmount, @Nullable Address refundAddress, @Nullable String memo,
             @Nullable byte[] merchantData) {
         if (refundAddress != null) {
             if (refundAmount == null)
@@ -387,7 +387,7 @@ public class PaymentProtocol {
      * @param address address to pay to
      * @return output
      */
-    public static Protos.Output createPayToAddressOutput(@Nullable BigInteger amount, Address address) {
+    public static Protos.Output createPayToAddressOutput(@Nullable Coin amount, Address address) {
         Protos.Output.Builder output = Protos.Output.newBuilder();
         if (amount != null) {
             if (amount.compareTo(NetworkParameters.MAX_MONEY) > 0)
@@ -404,10 +404,10 @@ public class PaymentProtocol {
      * Value object to hold amount/script pairs.
      */
     public static class Output implements Serializable {
-        public final @Nullable BigInteger amount;
+        public final @Nullable Coin amount;
         public final byte[] scriptData;
 
-        public Output(@Nullable BigInteger amount, byte[] scriptData) {
+        public Output(@Nullable Coin amount, byte[] scriptData) {
             this.amount = amount;
             this.scriptData = scriptData;
         }
diff --git a/core/src/main/java/com/google/bitcoin/protocols/payments/PaymentSession.java b/core/src/main/java/com/google/bitcoin/protocols/payments/PaymentSession.java
index af4fc2e4..98b41a83 100644
--- a/core/src/main/java/com/google/bitcoin/protocols/payments/PaymentSession.java
+++ b/core/src/main/java/com/google/bitcoin/protocols/payments/PaymentSession.java
@@ -30,7 +30,6 @@ import org.bitcoin.protocols.payments.Protos;
 import javax.annotation.Nullable;
 
 import java.io.*;
-import java.math.BigInteger;
 import java.net.*;
 import java.security.KeyStoreException;
 import java.util.ArrayList;
@@ -71,7 +70,7 @@ public class PaymentSession {
     private final TrustStoreLoader trustStoreLoader;
     private Protos.PaymentRequest paymentRequest;
     private Protos.PaymentDetails paymentDetails;
-    private BigInteger totalValue = BigInteger.ZERO;
+    private Coin totalValue = Coin.ZERO;
 
     /**
      * Stores the calculated PKI verification data, or null if none is available.
@@ -224,7 +223,7 @@ public class PaymentSession {
     public List<PaymentProtocol.Output> getOutputs() {
         List<PaymentProtocol.Output> outputs = new ArrayList<PaymentProtocol.Output>(paymentDetails.getOutputsCount());
         for (Protos.Output output : paymentDetails.getOutputsList()) {
-            BigInteger amount = output.hasAmount() ? BigInteger.valueOf(output.getAmount()) : null;
+            Coin amount = output.hasAmount() ? Coin.valueOf(output.getAmount()) : null;
             outputs.add(new PaymentProtocol.Output(amount, output.getScript().toByteArray()));
         }
         return outputs;
@@ -243,7 +242,7 @@ public class PaymentSession {
     /**
      * Returns the total amount of bitcoins requested.
      */
-    public BigInteger getValue() {
+    public Coin getValue() {
         return totalValue;
     }
 
@@ -297,7 +296,7 @@ public class PaymentSession {
     public Wallet.SendRequest getSendRequest() {
         Transaction tx = new Transaction(params);
         for (Protos.Output output : paymentDetails.getOutputsList())
-            tx.addOutput(new TransactionOutput(params, tx, BigInteger.valueOf(output.getAmount()), output.getScript().toByteArray()));
+            tx.addOutput(new TransactionOutput(params, tx, Coin.valueOf(output.getAmount()), output.getScript().toByteArray()));
         return Wallet.SendRequest.forTx(tx);
     }
 
@@ -397,7 +396,7 @@ public class PaymentSession {
                 throw new PaymentProtocolException.InvalidOutputs("No outputs");
             for (Protos.Output output : paymentDetails.getOutputsList()) {
                 if (output.hasAmount())
-                    totalValue = totalValue.add(BigInteger.valueOf(output.getAmount()));
+                    totalValue = totalValue.add(Coin.valueOf(output.getAmount()));
             }
             // This won't ever happen in practice. It would only happen if the user provided outputs
             // that are obviously invalid. Still, we don't want to silently overflow.
diff --git a/core/src/main/java/com/google/bitcoin/store/H2FullPrunedBlockStore.java b/core/src/main/java/com/google/bitcoin/store/H2FullPrunedBlockStore.java
index 45f30697..53e438ab 100644
--- a/core/src/main/java/com/google/bitcoin/store/H2FullPrunedBlockStore.java
+++ b/core/src/main/java/com/google/bitcoin/store/H2FullPrunedBlockStore.java
@@ -650,7 +650,7 @@ public class H2FullPrunedBlockStore implements FullPrunedBlockStore {
             }
             // Parse it.
             int height = results.getInt(1);
-            BigInteger value = new BigInteger(results.getBytes(2));
+            Coin value = new Coin(results.getBytes(2));
             // Tell the StoredTransactionOutput that we are a coinbase, as that is encoded in height
             return new StoredTransactionOutput(hash, index, value, height, true, results.getBytes(3));
         } catch (SQLException ex) {
diff --git a/core/src/main/java/com/google/bitcoin/store/PostgresFullPrunedBlockStore.java b/core/src/main/java/com/google/bitcoin/store/PostgresFullPrunedBlockStore.java
index 2a872198..ab5b482a 100644
--- a/core/src/main/java/com/google/bitcoin/store/PostgresFullPrunedBlockStore.java
+++ b/core/src/main/java/com/google/bitcoin/store/PostgresFullPrunedBlockStore.java
@@ -744,7 +744,7 @@ public class PostgresFullPrunedBlockStore implements FullPrunedBlockStore {
             }
             // Parse it.
             int height = results.getInt(1);
-            BigInteger value = new BigInteger(results.getBytes(2));
+            Coin value = new Coin(results.getBytes(2));
             // Tell the StoredTransactionOutput that we are a coinbase, as that is encoded in height
             StoredTransactionOutput txout = new StoredTransactionOutput(hash, index, value, height, true, results.getBytes(3));
             return txout;
diff --git a/core/src/main/java/com/google/bitcoin/store/WalletProtobufSerializer.java b/core/src/main/java/com/google/bitcoin/store/WalletProtobufSerializer.java
index 6b2199ee..e09461ee 100644
--- a/core/src/main/java/com/google/bitcoin/store/WalletProtobufSerializer.java
+++ b/core/src/main/java/com/google/bitcoin/store/WalletProtobufSerializer.java
@@ -503,7 +503,7 @@ public class WalletProtobufSerializer {
         }
         
         for (Protos.TransactionOutput outputProto : txProto.getTransactionOutputList()) {
-            BigInteger value = BigInteger.valueOf(outputProto.getValue());
+            Coin value = Coin.valueOf(outputProto.getValue());
             byte[] scriptBytes = outputProto.getScriptBytes().toByteArray();
             TransactionOutput output = new TransactionOutput(params, tx, value, scriptBytes);
             tx.addOutput(output);
@@ -515,7 +515,7 @@ public class WalletProtobufSerializer {
                     inputProto.getTransactionOutPointIndex() & 0xFFFFFFFFL,
                     byteStringToHash(inputProto.getTransactionOutPointHash())
             );
-            BigInteger value = inputProto.hasValue() ? BigInteger.valueOf(inputProto.getValue()) : null;
+            Coin value = inputProto.hasValue() ? Coin.valueOf(inputProto.getValue()) : null;
             TransactionInput input = new TransactionInput(params, tx, scriptBytes, outpoint, value);
             if (inputProto.hasSequence()) {
                 input.setSequenceNumber(inputProto.getSequence());
diff --git a/core/src/main/java/com/google/bitcoin/testing/FakeTxBuilder.java b/core/src/main/java/com/google/bitcoin/testing/FakeTxBuilder.java
index 3e214740..e94f2ac1 100644
--- a/core/src/main/java/com/google/bitcoin/testing/FakeTxBuilder.java
+++ b/core/src/main/java/com/google/bitcoin/testing/FakeTxBuilder.java
@@ -22,7 +22,6 @@ import com.google.bitcoin.store.BlockStoreException;
 
 import java.io.ByteArrayOutputStream;
 import java.io.IOException;
-import java.math.BigInteger;
 import java.nio.ByteBuffer;
 
 /**
@@ -33,7 +32,7 @@ public class FakeTxBuilder {
      * Create a fake TX of sufficient realism to exercise the unit tests. Two outputs, one to us, one to somewhere
      * else to simulate change. There is one random input.
      */
-    public static Transaction createFakeTxWithChangeAddress(NetworkParameters params, BigInteger nanocoins, Address to, Address changeOutput) {
+    public static Transaction createFakeTxWithChangeAddress(NetworkParameters params, Coin nanocoins, Address to, Address changeOutput) {
         Transaction t = new Transaction(params);
         TransactionOutput outputToMe = new TransactionOutput(params, t, nanocoins, to);
         t.addOutput(outputToMe);
@@ -54,7 +53,7 @@ public class FakeTxBuilder {
      * Create a fake TX of sufficient realism to exercise the unit tests. Two outputs, one to us, one to somewhere
      * else to simulate change. There is one random input.
      */
-    public static Transaction createFakeTx(NetworkParameters params, BigInteger nanocoins, Address to) {
+    public static Transaction createFakeTx(NetworkParameters params, Coin nanocoins, Address to) {
         return createFakeTxWithChangeAddress(params, nanocoins, to, new ECKey().toAddress(params));
     }
 
@@ -62,7 +61,7 @@ public class FakeTxBuilder {
      * Create a fake TX of sufficient realism to exercise the unit tests. Two outputs, one to us, one to somewhere
      * else to simulate change. There is one random input.
      */
-    public static Transaction createFakeTx(NetworkParameters params, BigInteger nanocoins, ECKey to) {
+    public static Transaction createFakeTx(NetworkParameters params, Coin nanocoins, ECKey to) {
         Transaction t = new Transaction(params);
         TransactionOutput outputToMe = new TransactionOutput(params, t, nanocoins, to);
         t.addOutput(outputToMe);
@@ -82,7 +81,7 @@ public class FakeTxBuilder {
     /**
      * Transaction[0] is a feeder transaction, supplying BTC to Transaction[1]
      */
-    public static Transaction[] createFakeTx(NetworkParameters params, BigInteger nanocoins,
+    public static Transaction[] createFakeTx(NetworkParameters params, Coin nanocoins,
                                              Address to, Address from) {
         // Create fake TXes of sufficient realism to exercise the unit tests. This transaction send BTC from the
         // from address, to the to address with to one to somewhere else to simulate change.
@@ -134,7 +133,7 @@ public class FakeTxBuilder {
      */
     public static DoubleSpends createFakeDoubleSpendTxns(NetworkParameters params, Address to) {
         DoubleSpends doubleSpends = new DoubleSpends();
-        BigInteger value = Utils.toNanoCoins(1, 0);
+        Coin value = Utils.toNanoCoins(1, 0);
         Address someBadGuy = new ECKey().toAddress(params);
 
         doubleSpends.t1 = new Transaction(params);
diff --git a/core/src/main/java/com/google/bitcoin/testing/TestWithNetworkConnections.java b/core/src/main/java/com/google/bitcoin/testing/TestWithNetworkConnections.java
index b0b99f83..774b8424 100644
--- a/core/src/main/java/com/google/bitcoin/testing/TestWithNetworkConnections.java
+++ b/core/src/main/java/com/google/bitcoin/testing/TestWithNetworkConnections.java
@@ -29,7 +29,6 @@ import com.google.common.util.concurrent.SettableFuture;
 import javax.annotation.Nullable;
 import javax.net.SocketFactory;
 import java.io.IOException;
-import java.math.BigInteger;
 import java.net.InetAddress;
 import java.net.InetSocketAddress;
 import java.net.SocketAddress;
@@ -82,7 +81,7 @@ public class TestWithNetworkConnections {
         BriefLogFormatter.init();
 
         unitTestParams = UnitTestParams.get();
-        Wallet.SendRequest.DEFAULT_FEE_PER_KB = BigInteger.ZERO;
+        Wallet.SendRequest.DEFAULT_FEE_PER_KB = Coin.ZERO;
         this.blockStore = blockStore;
         wallet = new Wallet(unitTestParams);
         key = wallet.freshReceiveKey();
diff --git a/core/src/main/java/com/google/bitcoin/testing/TestWithWallet.java b/core/src/main/java/com/google/bitcoin/testing/TestWithWallet.java
index ad784ac6..ff7ca8db 100644
--- a/core/src/main/java/com/google/bitcoin/testing/TestWithWallet.java
+++ b/core/src/main/java/com/google/bitcoin/testing/TestWithWallet.java
@@ -24,7 +24,6 @@ import com.google.bitcoin.utils.BriefLogFormatter;
 
 import javax.annotation.Nullable;
 import java.io.IOException;
-import java.math.BigInteger;
 
 import static com.google.bitcoin.testing.FakeTxBuilder.createFakeBlock;
 import static com.google.bitcoin.testing.FakeTxBuilder.createFakeTx;
@@ -49,7 +48,7 @@ public class TestWithWallet {
 
     public void setUp() throws Exception {
         BriefLogFormatter.init();
-        Wallet.SendRequest.DEFAULT_FEE_PER_KB = BigInteger.ZERO;
+        Wallet.SendRequest.DEFAULT_FEE_PER_KB = Coin.ZERO;
         wallet = new Wallet(params);
         myKey = wallet.currentReceiveKey();
         myAddress = myKey.toAddress(params);
@@ -83,17 +82,17 @@ public class TestWithWallet {
     }
 
     @Nullable
-    protected Transaction sendMoneyToWallet(Wallet wallet, BigInteger value, Address toAddress, AbstractBlockChain.NewBlockType type) throws IOException, VerificationException {
+    protected Transaction sendMoneyToWallet(Wallet wallet, Coin value, Address toAddress, AbstractBlockChain.NewBlockType type) throws IOException, VerificationException {
         return sendMoneyToWallet(wallet, createFakeTx(params, value, toAddress), type);
     }
 
     @Nullable
-    protected Transaction sendMoneyToWallet(Wallet wallet, BigInteger value, ECKey toPubKey, AbstractBlockChain.NewBlockType type) throws IOException, VerificationException {
+    protected Transaction sendMoneyToWallet(Wallet wallet, Coin value, ECKey toPubKey, AbstractBlockChain.NewBlockType type) throws IOException, VerificationException {
         return sendMoneyToWallet(wallet, createFakeTx(params, value, toPubKey), type);
     }
 
     @Nullable
-    protected Transaction sendMoneyToWallet(BigInteger value, AbstractBlockChain.NewBlockType type) throws IOException,  VerificationException {
+    protected Transaction sendMoneyToWallet(Coin value, AbstractBlockChain.NewBlockType type) throws IOException,  VerificationException {
         return sendMoneyToWallet(this.wallet, createFakeTx(params, value, myAddress), type);
     }
 }
diff --git a/core/src/main/java/com/google/bitcoin/uri/BitcoinURI.java b/core/src/main/java/com/google/bitcoin/uri/BitcoinURI.java
index 899c3846..f01a552b 100644
--- a/core/src/main/java/com/google/bitcoin/uri/BitcoinURI.java
+++ b/core/src/main/java/com/google/bitcoin/uri/BitcoinURI.java
@@ -20,14 +20,16 @@ package com.google.bitcoin.uri;
 
 import com.google.bitcoin.core.Address;
 import com.google.bitcoin.core.AddressFormatException;
+import com.google.bitcoin.core.Coin;
 import com.google.bitcoin.core.NetworkParameters;
 import com.google.bitcoin.core.Utils;
+
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
 import javax.annotation.Nullable;
+
 import java.io.UnsupportedEncodingException;
-import java.math.BigInteger;
 import java.net.URI;
 import java.net.URISyntaxException;
 import java.net.URLDecoder;
@@ -207,7 +209,7 @@ public class BitcoinURI {
             if (FIELD_AMOUNT.equals(nameToken)) {
                 // Decode the amount (contains an optional decimal component to 8dp).
                 try {
-                    BigInteger amount = Utils.toNanoCoins(valueToken);
+                    Coin amount = Utils.toNanoCoins(valueToken);
                     putWithValidation(FIELD_AMOUNT, amount);
                 } catch (NumberFormatException e) {
                     throw new OptionalFieldValidationException(String.format("'%s' is not a valid amount", valueToken), e);
@@ -263,8 +265,8 @@ public class BitcoinURI {
      * @return The amount name encoded using a pure integer value based at
      *         10,000,000 units is 1 BTC. May be null if no amount is specified
      */
-    public BigInteger getAmount() {
-        return (BigInteger) parameterMap.get(FIELD_AMOUNT);
+    public Coin getAmount() {
+        return (Coin) parameterMap.get(FIELD_AMOUNT);
     }
 
     /**
@@ -313,7 +315,7 @@ public class BitcoinURI {
         return builder.toString();
     }
 
-    public static String convertToBitcoinURI(Address address, BigInteger amount, String label, String message) {
+    public static String convertToBitcoinURI(Address address, Coin amount, String label, String message) {
         return convertToBitcoinURI(address.toString(), amount, label, message);
     }
 
@@ -326,11 +328,11 @@ public class BitcoinURI {
      * @param message A message
      * @return A String containing the Bitcoin URI
      */
-    public static String convertToBitcoinURI(String address, @Nullable BigInteger amount, @Nullable String label,
+    public static String convertToBitcoinURI(String address, @Nullable Coin amount, @Nullable String label,
                                              @Nullable String message) {
         checkNotNull(address);
         if (amount != null && amount.signum() < 0) {
-            throw new IllegalArgumentException("Amount must be positive");
+            throw new IllegalArgumentException("Coin must be positive");
         }
         
         StringBuilder builder = new StringBuilder();
diff --git a/core/src/main/java/com/google/bitcoin/wallet/CoinSelection.java b/core/src/main/java/com/google/bitcoin/wallet/CoinSelection.java
index 90104e8c..67cf40e1 100644
--- a/core/src/main/java/com/google/bitcoin/wallet/CoinSelection.java
+++ b/core/src/main/java/com/google/bitcoin/wallet/CoinSelection.java
@@ -1,22 +1,22 @@
 package com.google.bitcoin.wallet;
 
+import com.google.bitcoin.core.Coin;
 import com.google.bitcoin.core.TransactionOutput;
 
-import java.math.BigInteger;
 import java.util.Collection;
 
 /**
  * Represents the results of a
- * {@link com.google.bitcoin.wallet.CoinSelector#select(java.math.BigInteger, java.util.LinkedList)} operation. A
+ * {@link com.google.bitcoin.wallet.CoinSelector#select(java.math.Coin, java.util.LinkedList)} operation. A
  * coin selection represents a list of spendable transaction outputs that sum together to give valueGathered.
  * Different coin selections could be produced by different coin selectors from the same input set, according
  * to their varying policies.
  */
 public class CoinSelection {
-    public BigInteger valueGathered;
+    public Coin valueGathered;
     public Collection<TransactionOutput> gathered;
 
-    public CoinSelection(BigInteger valueGathered, Collection<TransactionOutput> gathered) {
+    public CoinSelection(Coin valueGathered, Collection<TransactionOutput> gathered) {
         this.valueGathered = valueGathered;
         this.gathered = gathered;
     }
diff --git a/core/src/main/java/com/google/bitcoin/wallet/CoinSelector.java b/core/src/main/java/com/google/bitcoin/wallet/CoinSelector.java
index d2b8f86d..10102d02 100644
--- a/core/src/main/java/com/google/bitcoin/wallet/CoinSelector.java
+++ b/core/src/main/java/com/google/bitcoin/wallet/CoinSelector.java
@@ -1,8 +1,8 @@
 package com.google.bitcoin.wallet;
 
+import com.google.bitcoin.core.Coin;
 import com.google.bitcoin.core.TransactionOutput;
 
-import java.math.BigInteger;
 import java.util.LinkedList;
 
 /**
@@ -17,5 +17,5 @@ public interface CoinSelector {
      * this call and can be edited freely. See the docs for CoinSelection to learn more, or look a the implementation
      * of {@link com.google.bitcoin.wallet.DefaultCoinSelector}.
      */
-    public CoinSelection select(BigInteger target, LinkedList<TransactionOutput> candidates);
+    public CoinSelection select(Coin target, LinkedList<TransactionOutput> candidates);
 }
diff --git a/core/src/main/java/com/google/bitcoin/wallet/DefaultCoinSelector.java b/core/src/main/java/com/google/bitcoin/wallet/DefaultCoinSelector.java
index a72171ff..f5efde00 100644
--- a/core/src/main/java/com/google/bitcoin/wallet/DefaultCoinSelector.java
+++ b/core/src/main/java/com/google/bitcoin/wallet/DefaultCoinSelector.java
@@ -1,5 +1,6 @@
 package com.google.bitcoin.wallet;
 
+import com.google.bitcoin.core.Coin;
 import com.google.bitcoin.core.NetworkParameters;
 import com.google.bitcoin.core.Transaction;
 import com.google.bitcoin.core.TransactionConfidence;
@@ -16,7 +17,7 @@ import java.util.*;
  * "spending" more priority than would be required to get the transaction we are creating confirmed.
  */
 public class DefaultCoinSelector implements CoinSelector {
-    public CoinSelection select(BigInteger biTarget, LinkedList<TransactionOutput> candidates) {
+    public CoinSelection select(Coin biTarget, LinkedList<TransactionOutput> candidates) {
         long target = biTarget.longValue();
         HashSet<TransactionOutput> selected = new HashSet<TransactionOutput>();
         // Sort the inputs by age*value so we get the highest "coindays" spent.
@@ -39,7 +40,7 @@ public class DefaultCoinSelector implements CoinSelector {
         }
         // Total may be lower than target here, if the given candidates were insufficient to create to requested
         // transaction.
-        return new CoinSelection(BigInteger.valueOf(total), selected);
+        return new CoinSelection(Coin.valueOf(total), selected);
     }
 
     @VisibleForTesting static void sortOutputs(ArrayList<TransactionOutput> outputs) {
@@ -53,10 +54,10 @@ public class DefaultCoinSelector implements CoinSelector {
                     depth1 = conf1.getDepthInBlocks();
                 if (conf2.getConfidenceType() == TransactionConfidence.ConfidenceType.BUILDING)
                     depth2 = conf2.getDepthInBlocks();
-                BigInteger aValue = a.getValue();
-                BigInteger bValue = b.getValue();
-                BigInteger aCoinDepth = aValue.multiply(BigInteger.valueOf(depth1));
-                BigInteger bCoinDepth = bValue.multiply(BigInteger.valueOf(depth2));
+                Coin aValue = a.getValue();
+                Coin bValue = b.getValue();
+                BigInteger aCoinDepth = aValue.toBigInteger().multiply(BigInteger.valueOf(depth1));
+                BigInteger bCoinDepth = bValue.toBigInteger().multiply(BigInteger.valueOf(depth2));
                 int c1 = bCoinDepth.compareTo(aCoinDepth);
                 if (c1 != 0) return c1;
                 // The "coin*days" destroyed are equal, sort by value alone to get the lowest transaction size.
diff --git a/core/src/main/java/com/google/bitcoin/wallet/DefaultRiskAnalysis.java b/core/src/main/java/com/google/bitcoin/wallet/DefaultRiskAnalysis.java
index 28c71c55..bea9d47f 100644
--- a/core/src/main/java/com/google/bitcoin/wallet/DefaultRiskAnalysis.java
+++ b/core/src/main/java/com/google/bitcoin/wallet/DefaultRiskAnalysis.java
@@ -17,6 +17,7 @@
 
 package com.google.bitcoin.wallet;
 
+import com.google.bitcoin.core.Coin;
 import com.google.bitcoin.core.NetworkParameters;
 import com.google.bitcoin.core.Transaction;
 import com.google.bitcoin.core.TransactionConfidence;
@@ -24,13 +25,11 @@ import com.google.bitcoin.core.TransactionInput;
 import com.google.bitcoin.core.TransactionOutput;
 import com.google.bitcoin.core.Wallet;
 import com.google.bitcoin.script.ScriptChunk;
-
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
 import javax.annotation.Nullable;
 
-import java.math.BigInteger;
 import java.util.List;
 
 import static com.google.common.base.Preconditions.checkState;
@@ -48,7 +47,7 @@ public class DefaultRiskAnalysis implements RiskAnalysis {
      * rejected by the network. Currently it's 546 satoshis. This is different from {@link Transaction#MIN_NONDUST_OUTPUT}
      * because of an upcoming fee change in Bitcoin Core 0.9.
      */
-    public static final BigInteger MIN_ANALYSIS_NONDUST_OUTPUT = BigInteger.valueOf(546);
+    public static final Coin MIN_ANALYSIS_NONDUST_OUTPUT = Coin.valueOf(546);
 
     protected final Transaction tx;
     protected final List<Transaction> dependencies;
diff --git a/core/src/main/java/com/google/bitcoin/wallet/KeyTimeCoinSelector.java b/core/src/main/java/com/google/bitcoin/wallet/KeyTimeCoinSelector.java
index e98f25b9..4f6fde91 100644
--- a/core/src/main/java/com/google/bitcoin/wallet/KeyTimeCoinSelector.java
+++ b/core/src/main/java/com/google/bitcoin/wallet/KeyTimeCoinSelector.java
@@ -22,7 +22,6 @@ import com.google.common.collect.Lists;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
-import java.math.BigInteger;
 import java.util.LinkedList;
 
 import static com.google.common.base.Preconditions.checkNotNull;
@@ -48,10 +47,10 @@ public class KeyTimeCoinSelector implements CoinSelector {
     }
 
     @Override
-    public CoinSelection select(BigInteger target, LinkedList<TransactionOutput> candidates) {
+    public CoinSelection select(Coin target, LinkedList<TransactionOutput> candidates) {
         try {
             LinkedList<TransactionOutput> gathered = Lists.newLinkedList();
-            BigInteger valueGathered = BigInteger.ZERO;
+            Coin valueGathered = Coin.ZERO;
             for (TransactionOutput output : candidates) {
                 if (ignorePending && !isConfirmed(output))
                     continue;
diff --git a/core/src/main/java/org/bitcoin/protocols/payments/Protos.java b/core/src/main/java/org/bitcoin/protocols/payments/Protos.java
index c36ec139..a0faa2fe 100644
--- a/core/src/main/java/org/bitcoin/protocols/payments/Protos.java
+++ b/core/src/main/java/org/bitcoin/protocols/payments/Protos.java
@@ -5978,7 +5978,7 @@ public final class Protos {
           internal_static_payments_Output_fieldAccessorTable = new
             com.google.protobuf.GeneratedMessage.FieldAccessorTable(
               internal_static_payments_Output_descriptor,
-              new java.lang.String[] { "Amount", "Script", });
+              new java.lang.String[] { "Coin", "Script", });
           internal_static_payments_PaymentDetails_descriptor =
             getDescriptor().getMessageTypes().get(1);
           internal_static_payments_PaymentDetails_fieldAccessorTable = new
diff --git a/core/src/test/java/com/google/bitcoin/core/BlockChainTest.java b/core/src/test/java/com/google/bitcoin/core/BlockChainTest.java
index dc3be653..48f3d134 100644
--- a/core/src/test/java/com/google/bitcoin/core/BlockChainTest.java
+++ b/core/src/test/java/com/google/bitcoin/core/BlockChainTest.java
@@ -65,7 +65,7 @@ public class BlockChainTest {
     public void setUp() throws Exception {
         BriefLogFormatter.initVerbose();
         testNetChain = new BlockChain(testNet, new Wallet(testNet), new MemoryBlockStore(testNet));
-        Wallet.SendRequest.DEFAULT_FEE_PER_KB = BigInteger.ZERO;
+        Wallet.SendRequest.DEFAULT_FEE_PER_KB = Coin.ZERO;
 
         unitTestParams = UnitTestParams.get();
         wallet = new Wallet(unitTestParams) {
@@ -278,7 +278,7 @@ public class BlockChainTest {
         b1.addTransaction(t2);
         b1.solve();
         chain.add(b1);
-        assertEquals(BigInteger.ZERO, wallet.getBalance());
+        assertEquals(Coin.ZERO, wallet.getBalance());
     }
 
     @Test
@@ -300,7 +300,7 @@ public class BlockChainTest {
         assertNotNull(coinbaseTransaction);
 
         // The coinbase tx is not yet available to spend.
-        assertEquals(BigInteger.ZERO, wallet.getBalance());
+        assertEquals(Coin.ZERO, wallet.getBalance());
         assertEquals(wallet.getBalance(BalanceType.ESTIMATED), Utils.toNanoCoins(50, 0));
         assertTrue(!coinbaseTransaction.isMature());
 
@@ -321,7 +321,7 @@ public class BlockChainTest {
             chain.add(b2);
 
             // Wallet still does not have the coinbase transaction available for spend.
-            assertEquals(BigInteger.ZERO, wallet.getBalance());
+            assertEquals(Coin.ZERO, wallet.getBalance());
             assertEquals(wallet.getBalance(BalanceType.ESTIMATED), Utils.toNanoCoins(50, 0));
 
             // The coinbase transaction is still not mature.
diff --git a/core/src/test/java/com/google/bitcoin/core/BlockTest.java b/core/src/test/java/com/google/bitcoin/core/BlockTest.java
index 73164fe8..87f7f07a 100644
--- a/core/src/test/java/com/google/bitcoin/core/BlockTest.java
+++ b/core/src/test/java/com/google/bitcoin/core/BlockTest.java
@@ -164,7 +164,7 @@ public class BlockTest {
         //assertTrue(tx.length == tx.bitcoinSerialize().length && tx.length == 8);
         byte[] outputScript = new byte[10];
         Arrays.fill(outputScript, (byte) ScriptOpCodes.OP_FALSE);
-        tx.addOutput(new TransactionOutput(params, null, BigInteger.valueOf(1), outputScript));
+        tx.addOutput(new TransactionOutput(params, null, Coin.valueOf(1), outputScript));
         tx.addInput(new TransactionInput(params, null, new byte[] {(byte) ScriptOpCodes.OP_FALSE},
                 new TransactionOutPoint(params, 0, Sha256Hash.create(new byte[] {1}))));
         int origTxLength = 8 + 2 + 8 + 1 + 10 + 40 + 1 + 1;
diff --git a/core/src/test/java/com/google/bitcoin/core/ChainSplitTest.java b/core/src/test/java/com/google/bitcoin/core/ChainSplitTest.java
index 28a0d2a1..cc167538 100644
--- a/core/src/test/java/com/google/bitcoin/core/ChainSplitTest.java
+++ b/core/src/test/java/com/google/bitcoin/core/ChainSplitTest.java
@@ -22,6 +22,7 @@ import com.google.bitcoin.store.MemoryBlockStore;
 import com.google.bitcoin.testing.FakeTxBuilder;
 import com.google.bitcoin.utils.BriefLogFormatter;
 import com.google.bitcoin.utils.Threading;
+
 import org.junit.Before;
 import org.junit.Test;
 import org.slf4j.Logger;
@@ -53,7 +54,7 @@ public class ChainSplitTest {
     public void setUp() throws Exception {
         BriefLogFormatter.init();
         Utils.setMockClock(); // Use mock clock
-        Wallet.SendRequest.DEFAULT_FEE_PER_KB = BigInteger.ZERO;
+        Wallet.SendRequest.DEFAULT_FEE_PER_KB = Coin.ZERO;
         unitTestParams = UnitTestParams.get();
         wallet = new Wallet(unitTestParams);
         ECKey key1 = wallet.freshReceiveKey();
@@ -164,11 +165,11 @@ public class ChainSplitTest {
         assertTrue(chain.add(b2));
         //     genesis -> b1 -> b2
         //                  \-> b3 -> b4
-        assertEquals(BigInteger.ZERO, wallet.getBalance());
+        assertEquals(Coin.ZERO, wallet.getBalance());
         Block b3 = b1.createNextBlock(coinsTo);
         Block b4 = b3.createNextBlock(someOtherGuy);
         assertTrue(chain.add(b3));
-        assertEquals(BigInteger.ZERO, wallet.getBalance());
+        assertEquals(Coin.ZERO, wallet.getBalance());
         assertTrue(chain.add(b4));
         assertEquals("50.00", Utils.bitcoinValueToFriendlyString(wallet.getBalance()));
     }
@@ -183,7 +184,7 @@ public class ChainSplitTest {
         Transaction spend = wallet.createSend(dest, Utils.toNanoCoins(10, 0));
         wallet.commitTx(spend);
         // Waiting for confirmation ... make it eligible for selection.
-        assertEquals(BigInteger.ZERO, wallet.getBalance());
+        assertEquals(Coin.ZERO, wallet.getBalance());
         spend.getConfidence().markBroadcastBy(new PeerAddress(InetAddress.getByAddress(new byte[]{1, 2, 3, 4})));
         spend.getConfidence().markBroadcastBy(new PeerAddress(InetAddress.getByAddress(new byte[]{5,6,7,8})));
         assertEquals(ConfidenceType.PENDING, spend.getConfidence().getConfidenceType());
@@ -276,7 +277,7 @@ public class ChainSplitTest {
         //         -> b2
         Block b2 = unitTestParams.getGenesisBlock().createNextBlock(coinsTo);
         chain.add(b2);
-        assertEquals(BigInteger.ZERO, wallet.getBalance());
+        assertEquals(Coin.ZERO, wallet.getBalance());
         // genesis -> b1 -> b3
         //         -> b2
         Block b3 = b1.createNextBlock(someOtherGuy);
@@ -399,7 +400,7 @@ public class ChainSplitTest {
         final ArrayList<Transaction> txns = new ArrayList<Transaction>(3);
         wallet.addEventListener(new AbstractWalletEventListener() {
             @Override
-            public void onCoinsReceived(Wallet wallet, Transaction tx, BigInteger prevBalance, BigInteger newBalance) {
+            public void onCoinsReceived(Wallet wallet, Transaction tx, Coin prevBalance, Coin newBalance) {
                 txns.add(tx);
             }
         });
@@ -552,7 +553,7 @@ public class ChainSplitTest {
         wallet.commitTx(t3);
         chain.add(FakeTxBuilder.makeSolvedTestBlock(b1, t2, t3));
 
-        final BigInteger coins0point98 = Utils.COIN.subtract(Utils.CENT).subtract(Utils.CENT);
+        final Coin coins0point98 = Utils.COIN.subtract(Utils.CENT).subtract(Utils.CENT);
         assertEquals(coins0point98, wallet.getBalance());
 
         // Now round trip the wallet and force a re-org.
@@ -577,7 +578,7 @@ public class ChainSplitTest {
         final ArrayList<Transaction> txns = new ArrayList<Transaction>(3);
         wallet.addEventListener(new AbstractWalletEventListener() {
             @Override
-            public void onCoinsReceived(Wallet wallet, Transaction tx, BigInteger prevBalance, BigInteger newBalance) {
+            public void onCoinsReceived(Wallet wallet, Transaction tx, Coin prevBalance, Coin newBalance) {
                 txns.add(tx);
             }
         }, Threading.SAME_THREAD);
diff --git a/core/src/test/java/com/google/bitcoin/core/CoinbaseBlockTest.java b/core/src/test/java/com/google/bitcoin/core/CoinbaseBlockTest.java
index c71c3c64..8616d634 100644
--- a/core/src/test/java/com/google/bitcoin/core/CoinbaseBlockTest.java
+++ b/core/src/test/java/com/google/bitcoin/core/CoinbaseBlockTest.java
@@ -42,7 +42,7 @@ public class CoinbaseBlockTest {
     private static final int BLOCK_OF_INTEREST = 169482;
     private static final int BLOCK_LENGTH_AS_HEX = 37357;
     private static final long BLOCK_NONCE = 3973947400L;
-    private static final BigInteger BALANCE_AFTER_BLOCK = BigInteger.valueOf(22223642);
+    private static final Coin BALANCE_AFTER_BLOCK = Coin.valueOf(22223642);
 
     @Test
     public void testReceiveCoinbaseTransaction() throws Exception {
@@ -70,7 +70,7 @@ public class CoinbaseBlockTest {
         wallet.importKey(miningKey);
 
         // Initial balance should be zero by construction.
-        assertEquals(BigInteger.ZERO, wallet.getBalance());
+        assertEquals(Coin.ZERO, wallet.getBalance());
 
         // Give the wallet the first transaction in the block - this is the coinbase tx.
         List<Transaction> transactions = block.getTransactions();
@@ -79,7 +79,7 @@ public class CoinbaseBlockTest {
 
         // Coinbase transaction should have been received successfully but be unavailable to spend (too young).
         assertEquals(BALANCE_AFTER_BLOCK, wallet.getBalance(BalanceType.ESTIMATED));
-        assertEquals(BigInteger.ZERO, wallet.getBalance(BalanceType.AVAILABLE));
+        assertEquals(Coin.ZERO, wallet.getBalance(BalanceType.AVAILABLE));
     }
 
     /**
diff --git a/core/src/test/java/com/google/bitcoin/core/FullBlockTestGenerator.java b/core/src/test/java/com/google/bitcoin/core/FullBlockTestGenerator.java
index f0389f68..6d0cd356 100644
--- a/core/src/test/java/com/google/bitcoin/core/FullBlockTestGenerator.java
+++ b/core/src/test/java/com/google/bitcoin/core/FullBlockTestGenerator.java
@@ -65,9 +65,9 @@ class Rule {
 
 class TransactionOutPointWithValue {
     public TransactionOutPoint outpoint;
-    public BigInteger value;
+    public Coin value;
     Script scriptPubKey;
-    public TransactionOutPointWithValue(TransactionOutPoint outpoint, BigInteger value, Script scriptPubKey) {
+    public TransactionOutPointWithValue(TransactionOutPoint outpoint, Coin value, Script scriptPubKey) {
         this.outpoint = outpoint;
         this.value = value;
         this.scriptPubKey = scriptPubKey;
@@ -217,7 +217,7 @@ public class FullBlockTestGenerator {
         //                                                    \-> b9 (4)
         //                      \-> b3 (1) -> b4 (2)
         //
-        Block b9 = createNextBlock(b6, chainHeadHeight + 5, out4, BigInteger.valueOf(1));
+        Block b9 = createNextBlock(b6, chainHeadHeight + 5, out4, Coin.valueOf(1));
         blocks.add(new BlockAndValidity(blockToHeightMap, b9, false, true, b6.getHash(), chainHeadHeight + 4, "b9"));
         
         // Create a fork that ends in a block with too much fee (the one that causes the reorg)
@@ -228,7 +228,7 @@ public class FullBlockTestGenerator {
         Block b10 = createNextBlock(b5, chainHeadHeight + 4, out3, null);
         blocks.add(new BlockAndValidity(blockToHeightMap, b10, true, false, b6.getHash(), chainHeadHeight + 4, "b10"));
         
-        Block b11 = createNextBlock(b10, chainHeadHeight + 5, out4, BigInteger.valueOf(1));
+        Block b11 = createNextBlock(b10, chainHeadHeight + 5, out4, Coin.valueOf(1));
         blocks.add(new BlockAndValidity(blockToHeightMap, b11, false, true, b6.getHash(), chainHeadHeight + 4, "b11"));
         
         // Try again, but with a valid fork first
@@ -254,7 +254,7 @@ public class FullBlockTestGenerator {
 
         TransactionOutPointWithValue out5 = spendableOutputs.poll();
 
-        Block b14 = createNextBlock(b13, chainHeadHeight + 6, out5, BigInteger.valueOf(1));
+        Block b14 = createNextBlock(b13, chainHeadHeight + 6, out5, Coin.valueOf(1));
         // This will be "validly" added, though its actually invalid, it will just be marked orphan
         // and will be discarded when an attempt is made to reorg to it.
         // TODO: Use a WeakReference to check that it is freed properly after the reorg
@@ -278,10 +278,10 @@ public class FullBlockTestGenerator {
             Transaction tx = new Transaction(params);
             byte[] outputScript = new byte[Block.MAX_BLOCK_SIGOPS - sigOps];
             Arrays.fill(outputScript, (byte) OP_CHECKSIG);
-            tx.addOutput(new TransactionOutput(params, tx, BigInteger.valueOf(1), outputScript));
+            tx.addOutput(new TransactionOutput(params, tx, Coin.valueOf(1), outputScript));
             addOnlyInputToTransaction(tx, new TransactionOutPointWithValue(
                     new TransactionOutPoint(params, 1, b15.getTransactions().get(1).getHash()),
-                    BigInteger.valueOf(1), b15.getTransactions().get(1).getOutputs().get(1).getScriptPubKey()));
+                    Coin.valueOf(1), b15.getTransactions().get(1).getOutputs().get(1).getScriptPubKey()));
             b15.addTransaction(tx);
         }
         b15.solve();
@@ -303,10 +303,10 @@ public class FullBlockTestGenerator {
             Transaction tx = new Transaction(params);
             byte[] outputScript = new byte[Block.MAX_BLOCK_SIGOPS - sigOps + 1];
             Arrays.fill(outputScript, (byte) OP_CHECKSIG);
-            tx.addOutput(new TransactionOutput(params, tx, BigInteger.valueOf(1), outputScript));
+            tx.addOutput(new TransactionOutput(params, tx, Coin.valueOf(1), outputScript));
             addOnlyInputToTransaction(tx, new TransactionOutPointWithValue(
                     new TransactionOutPoint(params, 1, b16.getTransactions().get(1).getHash()),
-                    BigInteger.valueOf(1), b16.getTransactions().get(1).getOutputs().get(1).getScriptPubKey()));
+                    Coin.valueOf(1), b16.getTransactions().get(1).getOutputs().get(1).getScriptPubKey()));
             b16.addTransaction(tx);
         }
         b16.solve();
@@ -321,10 +321,10 @@ public class FullBlockTestGenerator {
         Block b17 = createNextBlock(b15, chainHeadHeight + 7, out6, null);
         {
             Transaction tx = new Transaction(params);
-            tx.addOutput(new TransactionOutput(params, tx, BigInteger.valueOf(1), new byte[] {}));
+            tx.addOutput(new TransactionOutput(params, tx, Coin.valueOf(1), new byte[] {}));
             addOnlyInputToTransaction(tx, new TransactionOutPointWithValue(
                     new TransactionOutPoint(params, 1, b3.getTransactions().get(1).getHash()),
-                    BigInteger.valueOf(1), b3.getTransactions().get(1).getOutputs().get(1).getScriptPubKey()));
+                    Coin.valueOf(1), b3.getTransactions().get(1).getOutputs().get(1).getScriptPubKey()));
             b17.addTransaction(tx);
         }
         b17.solve();
@@ -339,10 +339,10 @@ public class FullBlockTestGenerator {
         Block b18 = createNextBlock(b13, chainHeadHeight + 6, out5, null);
         {
             Transaction tx = new Transaction(params);
-            tx.addOutput(new TransactionOutput(params, tx, BigInteger.valueOf(1), new byte[] {}));
+            tx.addOutput(new TransactionOutput(params, tx, Coin.valueOf(1), new byte[] {}));
             addOnlyInputToTransaction(tx, new TransactionOutPointWithValue(
                     new TransactionOutPoint(params, 1, b3.getTransactions().get(1).getHash()),
-                    BigInteger.valueOf(1), b3.getTransactions().get(1).getOutputs().get(1).getScriptPubKey()));
+                    Coin.valueOf(1), b3.getTransactions().get(1).getOutputs().get(1).getScriptPubKey()));
             b18.addTransaction(tx);
         }
         b18.solve();
@@ -384,10 +384,10 @@ public class FullBlockTestGenerator {
             // Signature size is non-deterministic, so it may take several runs before finding any off-by-one errors
             byte[] outputScript = new byte[Block.MAX_BLOCK_SIZE - b23.getMessageSize() - 138];
             Arrays.fill(outputScript, (byte) OP_FALSE);
-            tx.addOutput(new TransactionOutput(params, tx, BigInteger.valueOf(1), outputScript));
+            tx.addOutput(new TransactionOutput(params, tx, Coin.valueOf(1), outputScript));
             addOnlyInputToTransaction(tx, new TransactionOutPointWithValue(
                     new TransactionOutPoint(params, 1, b23.getTransactions().get(1).getHash()),
-                    BigInteger.valueOf(1), b23.getTransactions().get(1).getOutputs().get(1).getScriptPubKey()));
+                    Coin.valueOf(1), b23.getTransactions().get(1).getOutputs().get(1).getScriptPubKey()));
             b23.addTransaction(tx);
         }
         b23.solve();
@@ -403,10 +403,10 @@ public class FullBlockTestGenerator {
             // Signature size is non-deterministic, so it may take several runs before finding any off-by-one errors
             byte[] outputScript = new byte[Block.MAX_BLOCK_SIZE - b24.getMessageSize() - 135];
             Arrays.fill(outputScript, (byte) OP_FALSE);
-            tx.addOutput(new TransactionOutput(params, tx, BigInteger.valueOf(1), outputScript));
+            tx.addOutput(new TransactionOutput(params, tx, Coin.valueOf(1), outputScript));
             addOnlyInputToTransaction(tx, new TransactionOutPointWithValue(
                     new TransactionOutPoint(params, 1, b24.getTransactions().get(1).getHash()),
-                    BigInteger.valueOf(1), b24.getTransactions().get(1).getOutputs().get(1).getScriptPubKey()));
+                    Coin.valueOf(1), b24.getTransactions().get(1).getOutputs().get(1).getScriptPubKey()));
             b24.addTransaction(tx);
         }
         b24.solve();
@@ -479,10 +479,10 @@ public class FullBlockTestGenerator {
             Transaction tx = new Transaction(params);
             byte[] outputScript = new byte[(Block.MAX_BLOCK_SIGOPS - sigOps)/20];
             Arrays.fill(outputScript, (byte) OP_CHECKMULTISIG);
-            tx.addOutput(new TransactionOutput(params, tx, BigInteger.valueOf(1), outputScript));
+            tx.addOutput(new TransactionOutput(params, tx, Coin.valueOf(1), outputScript));
             addOnlyInputToTransaction(tx, new TransactionOutPointWithValue(
                     new TransactionOutPoint(params, 1, b31.getTransactions().get(1).getHash()),
-                    BigInteger.valueOf(1), b31.getTransactions().get(1).getOutputs().get(1).getScriptPubKey()));
+                    Coin.valueOf(1), b31.getTransactions().get(1).getOutputs().get(1).getScriptPubKey()));
             b31.addTransaction(tx);
         }
         b31.solve();
@@ -506,10 +506,10 @@ public class FullBlockTestGenerator {
             Arrays.fill(outputScript, (byte) OP_CHECKMULTISIG);
             for (int i = 0; i < (Block.MAX_BLOCK_SIGOPS - sigOps)%20; i++)
                 outputScript[i] = (byte) OP_CHECKSIG;
-            tx.addOutput(new TransactionOutput(params, tx, BigInteger.valueOf(1), outputScript));
+            tx.addOutput(new TransactionOutput(params, tx, Coin.valueOf(1), outputScript));
             addOnlyInputToTransaction(tx, new TransactionOutPointWithValue(
                     new TransactionOutPoint(params, 1, b32.getTransactions().get(1).getHash()),
-                    BigInteger.valueOf(1), b32.getTransactions().get(1).getOutputs().get(1).getScriptPubKey()));
+                    Coin.valueOf(1), b32.getTransactions().get(1).getOutputs().get(1).getScriptPubKey()));
             b32.addTransaction(tx);
         }
         b32.solve();
@@ -526,10 +526,10 @@ public class FullBlockTestGenerator {
             Transaction tx = new Transaction(params);
             byte[] outputScript = new byte[(Block.MAX_BLOCK_SIGOPS - sigOps)/20];
             Arrays.fill(outputScript, (byte) OP_CHECKMULTISIGVERIFY);
-            tx.addOutput(new TransactionOutput(params, tx, BigInteger.valueOf(1), outputScript));
+            tx.addOutput(new TransactionOutput(params, tx, Coin.valueOf(1), outputScript));
             addOnlyInputToTransaction(tx, new TransactionOutPointWithValue(
                     new TransactionOutPoint(params, 1, b33.getTransactions().get(1).getHash()),
-                    BigInteger.valueOf(1), b33.getTransactions().get(1).getOutputs().get(1).getScriptPubKey()));
+                    Coin.valueOf(1), b33.getTransactions().get(1).getOutputs().get(1).getScriptPubKey()));
             b33.addTransaction(tx);
         }
         b33.solve();
@@ -553,10 +553,10 @@ public class FullBlockTestGenerator {
             Arrays.fill(outputScript, (byte) OP_CHECKMULTISIGVERIFY);
             for (int i = 0; i < (Block.MAX_BLOCK_SIGOPS - sigOps)%20; i++)
                 outputScript[i] = (byte) OP_CHECKSIG;
-            tx.addOutput(new TransactionOutput(params, tx, BigInteger.valueOf(1), outputScript));
+            tx.addOutput(new TransactionOutput(params, tx, Coin.valueOf(1), outputScript));
             addOnlyInputToTransaction(tx, new TransactionOutPointWithValue(
                     new TransactionOutPoint(params, 1, b34.getTransactions().get(1).getHash()),
-                    BigInteger.valueOf(1), b34.getTransactions().get(1).getOutputs().get(1).getScriptPubKey()));
+                    Coin.valueOf(1), b34.getTransactions().get(1).getOutputs().get(1).getScriptPubKey()));
             b34.addTransaction(tx);
         }
         b34.solve();
@@ -573,10 +573,10 @@ public class FullBlockTestGenerator {
             Transaction tx = new Transaction(params);
             byte[] outputScript = new byte[Block.MAX_BLOCK_SIGOPS - sigOps];
             Arrays.fill(outputScript, (byte) OP_CHECKSIGVERIFY);
-            tx.addOutput(new TransactionOutput(params, tx, BigInteger.valueOf(1), outputScript));
+            tx.addOutput(new TransactionOutput(params, tx, Coin.valueOf(1), outputScript));
             addOnlyInputToTransaction(tx, new TransactionOutPointWithValue(
                     new TransactionOutPoint(params, 1, b35.getTransactions().get(1).getHash()),
-                    BigInteger.valueOf(1), b35.getTransactions().get(1).getOutputs().get(1).getScriptPubKey()));
+                    Coin.valueOf(1), b35.getTransactions().get(1).getOutputs().get(1).getScriptPubKey()));
             b35.addTransaction(tx);
         }
         b35.solve();
@@ -598,10 +598,10 @@ public class FullBlockTestGenerator {
             Transaction tx = new Transaction(params);
             byte[] outputScript = new byte[Block.MAX_BLOCK_SIGOPS - sigOps + 1];
             Arrays.fill(outputScript, (byte) OP_CHECKSIGVERIFY);
-            tx.addOutput(new TransactionOutput(params, tx, BigInteger.valueOf(1), outputScript));
+            tx.addOutput(new TransactionOutput(params, tx, Coin.valueOf(1), outputScript));
             addOnlyInputToTransaction(tx, new TransactionOutPointWithValue(
                     new TransactionOutPoint(params, 1, b36.getTransactions().get(1).getHash()),
-                    BigInteger.valueOf(1), b36.getTransactions().get(1).getOutputs().get(1).getScriptPubKey()));
+                    Coin.valueOf(1), b36.getTransactions().get(1).getOutputs().get(1).getScriptPubKey()));
             b36.addTransaction(tx);
         }
         b36.solve();
@@ -618,7 +618,7 @@ public class FullBlockTestGenerator {
         Block b37 = createNextBlock(b35, chainHeadHeight + 12, out11, null);
         {
             Transaction tx = new Transaction(params);
-            tx.addOutput(new TransactionOutput(params, tx, BigInteger.valueOf(1), new byte[] {}));
+            tx.addOutput(new TransactionOutput(params, tx, Coin.valueOf(1), new byte[] {}));
             addOnlyInputToTransaction(tx, out11); // double spend out11
             b37.addTransaction(tx);
         }
@@ -628,11 +628,11 @@ public class FullBlockTestGenerator {
         Block b38 = createNextBlock(b35, chainHeadHeight + 12, out11, null);
         {
             Transaction tx = new Transaction(params);
-            tx.addOutput(new TransactionOutput(params, tx, BigInteger.valueOf(1), new byte[] {}));
+            tx.addOutput(new TransactionOutput(params, tx, Coin.valueOf(1), new byte[] {}));
             // Attempt to spend b37's first non-coinbase tx, at which point b37 was still considered valid
             addOnlyInputToTransaction(tx, new TransactionOutPointWithValue(
                     new TransactionOutPoint(params, 1, b37.getTransactions().get(1).getHash()),
-                    BigInteger.valueOf(1), b37.getTransactions().get(1).getOutputs().get(1).getScriptPubKey()));
+                    Coin.valueOf(1), b37.getTransactions().get(1).getOutputs().get(1).getScriptPubKey()));
             b38.addTransaction(tx);
         }
         b38.solve();
@@ -676,11 +676,11 @@ public class FullBlockTestGenerator {
             }
             scriptPubKey.write(OP_EQUAL);
             
-            BigInteger lastOutputValue = out11.value.subtract(BigInteger.valueOf(1));
+            Coin lastOutputValue = out11.value.subtract(Coin.valueOf(1));
             TransactionOutPoint lastOutPoint;
             {
                 Transaction tx = new Transaction(params);
-                tx.addOutput(new TransactionOutput(params, tx, BigInteger.valueOf(1), scriptPubKey.toByteArray()));
+                tx.addOutput(new TransactionOutput(params, tx, Coin.valueOf(1), scriptPubKey.toByteArray()));
                 tx.addOutput(new TransactionOutput(params, tx, lastOutputValue, new byte[]{OP_1}));
                 addOnlyInputToTransaction(tx, out11);
                 lastOutPoint = new TransactionOutPoint(params, 1, tx.getHash());
@@ -692,8 +692,8 @@ public class FullBlockTestGenerator {
             {
                 Transaction tx = new Transaction(params);
 
-                lastOutputValue = lastOutputValue.subtract(BigInteger.valueOf(1));
-                tx.addOutput(new TransactionOutput(params, tx, BigInteger.valueOf(1), scriptPubKey.toByteArray()));
+                lastOutputValue = lastOutputValue.subtract(Coin.valueOf(1));
+                tx.addOutput(new TransactionOutput(params, tx, Coin.valueOf(1), scriptPubKey.toByteArray()));
                 tx.addOutput(new TransactionOutput(params, tx, lastOutputValue, new byte[]{OP_1}));
                 tx.addInput(new TransactionInput(params, tx, new byte[]{OP_1}, lastOutPoint));
                 lastOutPoint = new TransactionOutPoint(params, 1, tx.getHash());
@@ -729,7 +729,7 @@ public class FullBlockTestGenerator {
             byte[] scriptSig = null;
             for (int i = 1; i <= numTxes; i++) {
                 Transaction tx = new Transaction(params);
-                tx.addOutput(new TransactionOutput(params, tx, BigInteger.valueOf(1), new byte[] {OP_1}));
+                tx.addOutput(new TransactionOutput(params, tx, Coin.valueOf(1), new byte[] {OP_1}));
                 tx.addInput(new TransactionInput(params, tx, new byte[]{OP_1}, lastOutPoint));
                 
                 TransactionInput input = new TransactionInput(params, tx, new byte[]{},
@@ -770,7 +770,7 @@ public class FullBlockTestGenerator {
             tx.addInput(new TransactionInput(params, tx, new byte[]{OP_1}, lastOutPoint));
             byte[] scriptPubKey = new byte[Block.MAX_BLOCK_SIGOPS - sigOps + 1];
             Arrays.fill(scriptPubKey, (byte) OP_CHECKSIG);
-            tx.addOutput(new TransactionOutput(params, tx, BigInteger.ZERO, scriptPubKey));
+            tx.addOutput(new TransactionOutput(params, tx, Coin.ZERO, scriptPubKey));
             b40.addTransaction(tx);
         }
         b40.solve();
@@ -795,7 +795,7 @@ public class FullBlockTestGenerator {
                 byte[] scriptSig = null;
                 for (int i = 1; i <= numTxes; i++) {
                     Transaction tx = new Transaction(params);
-                    tx.addOutput(new TransactionOutput(params, tx, BigInteger
+                    tx.addOutput(new TransactionOutput(params, tx, Coin
                             .valueOf(1), new byte[] {OP_1}));
                     tx.addInput(new TransactionInput(params, tx,
                             new byte[] {OP_1}, lastOutPoint));
@@ -847,7 +847,7 @@ public class FullBlockTestGenerator {
                         new byte[] {OP_1}, lastOutPoint));
                 byte[] scriptPubKey = new byte[Block.MAX_BLOCK_SIGOPS - sigOps];
                 Arrays.fill(scriptPubKey, (byte) OP_CHECKSIG);
-                tx.addOutput(new TransactionOutput(params, tx, BigInteger.ZERO, scriptPubKey));
+                tx.addOutput(new TransactionOutput(params, tx, Coin.ZERO, scriptPubKey));
                 b41.addTransaction(tx);
             }
             b41.solve();
@@ -885,14 +885,14 @@ public class FullBlockTestGenerator {
         byte[] outScriptBytes = ScriptBuilder.createOutputScript(ECKey.fromPublicOnly(coinbaseOutKeyPubKey)).getProgram();
         {
             b44.setDifficultyTarget(b43.getDifficultyTarget());
-            b44.addCoinbaseTransaction(coinbaseOutKeyPubKey, BigInteger.ZERO);
+            b44.addCoinbaseTransaction(coinbaseOutKeyPubKey, Coin.ZERO);
             
             Transaction t = new Transaction(params);
             // Entirely invalid scriptPubKey to ensure we aren't pre-verifying too much
-            t.addOutput(new TransactionOutput(params, t, BigInteger.valueOf(0), new byte[] {OP_PUSHDATA1 - 1 }));
-            t.addOutput(new TransactionOutput(params, t, BigInteger.valueOf(1), outScriptBytes));
+            t.addOutput(new TransactionOutput(params, t, Coin.valueOf(0), new byte[] {OP_PUSHDATA1 - 1 }));
+            t.addOutput(new TransactionOutput(params, t, Coin.valueOf(1), outScriptBytes));
             // Spendable output
-            t.addOutput(new TransactionOutput(params, t, BigInteger.ZERO, new byte[] {OP_1}));
+            t.addOutput(new TransactionOutput(params, t, Coin.ZERO, new byte[] {OP_1}));
             addOnlyInputToTransaction(t, out14);
             b44.addTransaction(t);
 
@@ -912,10 +912,10 @@ public class FullBlockTestGenerator {
             
             Transaction t = new Transaction(params);
             // Entirely invalid scriptPubKey to ensure we aren't pre-verifying too much
-            t.addOutput(new TransactionOutput(params, t, BigInteger.valueOf(0), new byte[] {OP_PUSHDATA1 - 1 }));
-            t.addOutput(new TransactionOutput(params, t, BigInteger.valueOf(1), outScriptBytes));
+            t.addOutput(new TransactionOutput(params, t, Coin.valueOf(0), new byte[] {OP_PUSHDATA1 - 1 }));
+            t.addOutput(new TransactionOutput(params, t, Coin.valueOf(1), outScriptBytes));
             // Spendable output
-            t.addOutput(new TransactionOutput(params, t, BigInteger.ZERO, new byte[] {OP_1}));
+            t.addOutput(new TransactionOutput(params, t, Coin.ZERO, new byte[] {OP_1}));
             addOnlyInputToTransaction(t, out15);
             try {
                 b45.addTransaction(t);
@@ -989,7 +989,7 @@ public class FullBlockTestGenerator {
         {
             Transaction coinbase = new Transaction(params);
             coinbase.addInput(new TransactionInput(params, coinbase, new byte[]{(byte) 0xff, 110, 1}));
-            coinbase.addOutput(new TransactionOutput(params, coinbase, BigInteger.ONE, outScriptBytes));
+            coinbase.addOutput(new TransactionOutput(params, coinbase, Coin.ONE, outScriptBytes));
             b51.addTransaction(coinbase, false);
         }
         b51.solve();
@@ -999,10 +999,10 @@ public class FullBlockTestGenerator {
         Block b52 = createNextBlock(b44, chainHeadHeight + 16, out15, null);
         {
             Transaction tx = new Transaction(params);
-            tx.addOutput(new TransactionOutput(params, tx, BigInteger.valueOf(1), new byte[] {}));
+            tx.addOutput(new TransactionOutput(params, tx, Coin.valueOf(1), new byte[] {}));
             addOnlyInputToTransaction(tx, new TransactionOutPointWithValue(
                     new TransactionOutPoint(params, 1, b52.getTransactions().get(1).getHash()),
-                    BigInteger.valueOf(1), b52.getTransactions().get(1).getOutputs().get(1).getScriptPubKey()));
+                    Coin.valueOf(1), b52.getTransactions().get(1).getOutputs().get(1).getScriptPubKey()));
             b52.addTransaction(tx);
             b52.addTransaction(tx);
         }
@@ -1047,10 +1047,10 @@ public class FullBlockTestGenerator {
         Transaction b56txToDuplicate;
         {
             b56txToDuplicate = new Transaction(params);
-            b56txToDuplicate.addOutput(new TransactionOutput(params, b56txToDuplicate, BigInteger.valueOf(1), new byte[] {}));
+            b56txToDuplicate.addOutput(new TransactionOutput(params, b56txToDuplicate, Coin.valueOf(1), new byte[] {}));
             addOnlyInputToTransaction(b56txToDuplicate, new TransactionOutPointWithValue(
                     new TransactionOutPoint(params, 1, b57.getTransactions().get(1).getHash()),
-                    BigInteger.valueOf(1), b57.getTransactions().get(1).getOutputs().get(1).getScriptPubKey()));
+                    Coin.valueOf(1), b57.getTransactions().get(1).getOutputs().get(1).getScriptPubKey()));
             b57.addTransaction(b56txToDuplicate);
         }
         b57.solve();
@@ -1081,7 +1081,7 @@ public class FullBlockTestGenerator {
         Block b58 = createNextBlock(b57, chainHeadHeight + 18, out17, null);
         {
             Transaction tx = new Transaction(params);
-            tx.addOutput(new TransactionOutput(params, tx, BigInteger.ZERO, new byte[] {}));
+            tx.addOutput(new TransactionOutput(params, tx, Coin.ZERO, new byte[] {}));
             tx.addInput(new TransactionInput(params, tx, new byte[] {OP_1},
                     new TransactionOutPoint(params, 3, b58.getTransactions().get(1).getHash())));
             b58.addTransaction(tx);
@@ -1094,7 +1094,7 @@ public class FullBlockTestGenerator {
         {
             Transaction tx = new Transaction(params);
             tx.addOutput(new TransactionOutput(params, tx,
-                    b59.getTransactions().get(1).getOutputs().get(2).getValue().add(BigInteger.ONE), new byte[] {}));
+                    b59.getTransactions().get(1).getOutputs().get(2).getValue().add(Coin.ONE), new byte[] {}));
             tx.addInput(new TransactionInput(params, tx, new byte[] {OP_1},
                     new TransactionOutPoint(params, 2, b59.getTransactions().get(1).getHash())));
             b59.addTransaction(tx);
@@ -1132,7 +1132,7 @@ public class FullBlockTestGenerator {
         {
             Transaction tx = new Transaction(params);
             tx.setLockTime(0xffffffffL);
-            tx.addOutput(new TransactionOutput(params, tx, BigInteger.ZERO, new byte[] {OP_TRUE}));
+            tx.addOutput(new TransactionOutput(params, tx, Coin.ZERO, new byte[] {OP_TRUE}));
             addOnlyInputToTransaction(tx, out18, 0);
             b62.addTransaction(tx);
             Preconditions.checkState(!tx.isFinal(chainHeadHeight + 17, b62.getTimeSeconds()));
@@ -1164,10 +1164,10 @@ public class FullBlockTestGenerator {
             // Signature size is non-deterministic, so it may take several runs before finding any off-by-one errors
             byte[] outputScript = new byte[Block.MAX_BLOCK_SIZE - b64Created.getMessageSize() - 138];
             Arrays.fill(outputScript, (byte) OP_FALSE);
-            tx.addOutput(new TransactionOutput(params, tx, BigInteger.valueOf(1), outputScript));
+            tx.addOutput(new TransactionOutput(params, tx, Coin.valueOf(1), outputScript));
             addOnlyInputToTransaction(tx, new TransactionOutPointWithValue(
                     new TransactionOutPoint(params, 1, b64Created.getTransactions().get(1).getHash()),
-                    BigInteger.valueOf(1), b64Created.getTransactions().get(1).getOutputs().get(1).getScriptPubKey()));
+                    Coin.valueOf(1), b64Created.getTransactions().get(1).getOutputs().get(1).getScriptPubKey()));
             b64Created.addTransaction(tx);
             b64Created.solve();
             
@@ -1210,7 +1210,7 @@ public class FullBlockTestGenerator {
             addOnlyInputToTransaction(tx1, out19, 0);
             b65.addTransaction(tx1);
             Transaction tx2 = new Transaction(params);
-            tx2.addOutput(new TransactionOutput(params, tx2, BigInteger.ZERO, new byte[]{OP_TRUE}));
+            tx2.addOutput(new TransactionOutput(params, tx2, Coin.ZERO, new byte[]{OP_TRUE}));
             tx2.addInput(new TransactionInput(params, tx2, new byte[]{OP_TRUE},
                     new TransactionOutPoint(params, 0, tx1.getHash())));
             b65.addTransaction(tx2);
@@ -1234,7 +1234,7 @@ public class FullBlockTestGenerator {
             tx1.addOutput(new TransactionOutput(params, tx1, out20.value, new byte[]{OP_TRUE}));
             addOnlyInputToTransaction(tx1, out20, 0);
             Transaction tx2 = new Transaction(params);
-            tx2.addOutput(new TransactionOutput(params, tx2, BigInteger.ZERO, new byte[]{OP_TRUE}));
+            tx2.addOutput(new TransactionOutput(params, tx2, Coin.ZERO, new byte[]{OP_TRUE}));
             tx2.addInput(new TransactionInput(params, tx2, new byte[]{OP_TRUE},
                     new TransactionOutPoint(params, 0, tx1.getHash())));
             b66.addTransaction(tx2);
@@ -1254,7 +1254,7 @@ public class FullBlockTestGenerator {
             addOnlyInputToTransaction(tx1, out20, 0);
             b67.addTransaction(tx1);
             Transaction tx2 = new Transaction(params);
-            tx2.addOutput(new TransactionOutput(params, tx2, BigInteger.ZERO, new byte[]{OP_TRUE}));
+            tx2.addOutput(new TransactionOutput(params, tx2, Coin.ZERO, new byte[]{OP_TRUE}));
             tx2.addInput(new TransactionInput(params, tx2, new byte[]{OP_TRUE},
                     new TransactionOutPoint(params, 0, tx1.getHash())));
             b67.addTransaction(tx2);
@@ -1271,20 +1271,20 @@ public class FullBlockTestGenerator {
         // -> b43 (13) -> b53 (14) -> b55 (15) -> b57 (16) -> b60 (17) -> b64 (18) -> b65 (19) -> b69 (20)
         //                                                                                    \-> b68 (20)
         //
-        Block b68 = createNextBlock(b65, chainHeadHeight + 21, null, BigInteger.TEN);
+        Block b68 = createNextBlock(b65, chainHeadHeight + 21, null, Coin.TEN);
         {
             Transaction tx = new Transaction(params);
-            tx.addOutput(new TransactionOutput(params, tx, out20.value.subtract(BigInteger.valueOf(9)), new byte[]{OP_TRUE}));
+            tx.addOutput(new TransactionOutput(params, tx, out20.value.subtract(Coin.valueOf(9)), new byte[]{OP_TRUE}));
             addOnlyInputToTransaction(tx, out20, 0);
             b68.addTransaction(tx);
         }
         b68.solve();
         blocks.add(new BlockAndValidity(blockToHeightMap, b68, false, true, b65.getHash(), chainHeadHeight + 20, "b68"));
         
-        Block b69 = createNextBlock(b65, chainHeadHeight + 21, null, BigInteger.TEN);
+        Block b69 = createNextBlock(b65, chainHeadHeight + 21, null, Coin.TEN);
         {
             Transaction tx = new Transaction(params);
-            tx.addOutput(new TransactionOutput(params, tx, out20.value.subtract(BigInteger.TEN), new byte[]{OP_TRUE}));
+            tx.addOutput(new TransactionOutput(params, tx, out20.value.subtract(Coin.TEN), new byte[]{OP_TRUE}));
             addOnlyInputToTransaction(tx, out20, 0);
             b69.addTransaction(tx);
         }
@@ -1304,7 +1304,7 @@ public class FullBlockTestGenerator {
         Block b70 = createNextBlock(b69, chainHeadHeight + 22, out21, null);
         {
             Transaction tx = new Transaction(params);
-            tx.addOutput(new TransactionOutput(params, tx, BigInteger.ZERO, new byte[]{OP_TRUE}));
+            tx.addOutput(new TransactionOutput(params, tx, Coin.ZERO, new byte[]{OP_TRUE}));
             tx.addInput(new TransactionInput(params, tx, new byte[]{OP_TRUE},
                     new TransactionOutPoint(params, 0, new Sha256Hash("23c70ed7c0506e9178fc1a987f40a33946d4ad4c962b5ae3a52546da53af0c5c"))));
             b70.addTransaction(tx);
@@ -1319,10 +1319,10 @@ public class FullBlockTestGenerator {
         Block b72 = createNextBlock(b69, chainHeadHeight + 22, out21, null);
         {
             Transaction tx = new Transaction(params);
-            tx.addOutput(new TransactionOutput(params, tx, BigInteger.ZERO, new byte[]{OP_TRUE}));
+            tx.addOutput(new TransactionOutput(params, tx, Coin.ZERO, new byte[]{OP_TRUE}));
             addOnlyInputToTransaction(tx, new TransactionOutPointWithValue(
                     new TransactionOutPoint(params, 1, b72.getTransactions().get(1).getHash()),
-                    BigInteger.valueOf(1), b72.getTransactions().get(1).getOutputs().get(1).getScriptPubKey()));
+                    Coin.valueOf(1), b72.getTransactions().get(1).getOutputs().get(1).getScriptPubKey()));
             b72.addTransaction(tx);
         }
         b72.solve();
@@ -1356,10 +1356,10 @@ public class FullBlockTestGenerator {
             // If we push an element that is too large, the CHECKSIGs after that push are still counted
             outputScript[Block.MAX_BLOCK_SIGOPS - sigOps] = OP_PUSHDATA4;
             Utils.uint32ToByteArrayLE(Script.MAX_SCRIPT_ELEMENT_SIZE + 1, outputScript, Block.MAX_BLOCK_SIGOPS - sigOps + 1);
-            tx.addOutput(new TransactionOutput(params, tx, BigInteger.valueOf(1), outputScript));
+            tx.addOutput(new TransactionOutput(params, tx, Coin.valueOf(1), outputScript));
             addOnlyInputToTransaction(tx, new TransactionOutPointWithValue(
                     new TransactionOutPoint(params, 1, b73.getTransactions().get(1).getHash()),
-                    BigInteger.valueOf(1), b73.getTransactions().get(1).getOutputs().get(1).getScriptPubKey()));
+                    Coin.valueOf(1), b73.getTransactions().get(1).getOutputs().get(1).getScriptPubKey()));
             b73.addTransaction(tx);
         }
         b73.solve();
@@ -1380,10 +1380,10 @@ public class FullBlockTestGenerator {
             outputScript[Block.MAX_BLOCK_SIGOPS - sigOps + 3] = (byte)0xff;
             outputScript[Block.MAX_BLOCK_SIGOPS - sigOps + 4] = (byte)0xff;
             outputScript[Block.MAX_BLOCK_SIGOPS - sigOps + 5] = (byte)0xff;
-            tx.addOutput(new TransactionOutput(params, tx, BigInteger.valueOf(1), outputScript));
+            tx.addOutput(new TransactionOutput(params, tx, Coin.valueOf(1), outputScript));
             addOnlyInputToTransaction(tx, new TransactionOutPointWithValue(
                     new TransactionOutPoint(params, 1, b74.getTransactions().get(1).getHash()),
-                    BigInteger.valueOf(1), b74.getTransactions().get(1).getOutputs().get(1).getScriptPubKey()));
+                    Coin.valueOf(1), b74.getTransactions().get(1).getOutputs().get(1).getScriptPubKey()));
             b74.addTransaction(tx);
         }
         b74.solve();
@@ -1404,10 +1404,10 @@ public class FullBlockTestGenerator {
             outputScript[Block.MAX_BLOCK_SIGOPS - sigOps + 2] = (byte)0xff;
             outputScript[Block.MAX_BLOCK_SIGOPS - sigOps + 3] = (byte)0xff;
             outputScript[Block.MAX_BLOCK_SIGOPS - sigOps + 4] = (byte)0xff;
-            tx.addOutput(new TransactionOutput(params, tx, BigInteger.valueOf(1), outputScript));
+            tx.addOutput(new TransactionOutput(params, tx, Coin.valueOf(1), outputScript));
             addOnlyInputToTransaction(tx, new TransactionOutPointWithValue(
                     new TransactionOutPoint(params, 1, b75.getTransactions().get(1).getHash()),
-                    BigInteger.valueOf(1), b75.getTransactions().get(1).getOutputs().get(1).getScriptPubKey()));
+                    Coin.valueOf(1), b75.getTransactions().get(1).getOutputs().get(1).getScriptPubKey()));
             b75.addTransaction(tx);
         }
         b75.solve();
@@ -1431,10 +1431,10 @@ public class FullBlockTestGenerator {
             // If we push an element that is filled with CHECKSIGs, they (obviously) arent counted
             outputScript[Block.MAX_BLOCK_SIGOPS - sigOps] = OP_PUSHDATA4;
             Utils.uint32ToByteArrayLE(Block.MAX_BLOCK_SIGOPS, outputScript, Block.MAX_BLOCK_SIGOPS - sigOps + 1);
-            tx.addOutput(new TransactionOutput(params, tx, BigInteger.valueOf(1), outputScript));
+            tx.addOutput(new TransactionOutput(params, tx, Coin.valueOf(1), outputScript));
             addOnlyInputToTransaction(tx, new TransactionOutPointWithValue(
                     new TransactionOutPoint(params, 1, b76.getTransactions().get(1).getHash()),
-                    BigInteger.valueOf(1), b76.getTransactions().get(1).getOutputs().get(1).getScriptPubKey()));
+                    Coin.valueOf(1), b76.getTransactions().get(1).getOutputs().get(1).getScriptPubKey()));
             b76.addTransaction(tx);
         }
         b76.solve();
@@ -1460,10 +1460,10 @@ public class FullBlockTestGenerator {
         Block b78 = createNextBlock(b77, chainHeadHeight + 26, out25, null);
         Transaction b78tx = new Transaction(params);
         {
-            b78tx.addOutput(new TransactionOutput(params, b78tx, BigInteger.ZERO, new byte[]{OP_TRUE}));
+            b78tx.addOutput(new TransactionOutput(params, b78tx, Coin.ZERO, new byte[]{OP_TRUE}));
             addOnlyInputToTransaction(b78tx, new TransactionOutPointWithValue(
                     new TransactionOutPoint(params, 1, b77.getTransactions().get(1).getHash()),
-                    BigInteger.valueOf(1), b77.getTransactions().get(1).getOutputs().get(1).getScriptPubKey()));
+                    Coin.valueOf(1), b77.getTransactions().get(1).getOutputs().get(1).getScriptPubKey()));
             b78.addTransaction(b78tx);
         }
         b78.solve();
@@ -1472,7 +1472,7 @@ public class FullBlockTestGenerator {
         Block b79 = createNextBlock(b78, chainHeadHeight + 27, out26, null);
         Transaction b79tx = new Transaction(params);
         {
-            b79tx.addOutput(new TransactionOutput(params, b79tx, BigInteger.ZERO, new byte[]{OP_TRUE}));
+            b79tx.addOutput(new TransactionOutput(params, b79tx, Coin.ZERO, new byte[]{OP_TRUE}));
             b79tx.addInput(new TransactionInput(params, b79tx, new byte[]{OP_TRUE}, new TransactionOutPoint(params, 0, b78tx.getHash())));
             b79.addTransaction(b79tx);
         }
@@ -1541,8 +1541,8 @@ public class FullBlockTestGenerator {
                 while (block.getMessageSize() < Block.MAX_BLOCK_SIZE - 500) {
                     Transaction tx = new Transaction(params);
                     tx.addInput(new TransactionInput(params, tx, new byte[] { OP_TRUE }, lastOutput));
-                    tx.addOutput(new TransactionOutput(params, tx, BigInteger.ZERO, new byte[] { OP_TRUE }));
-                    tx.addOutput(new TransactionOutput(params, tx, BigInteger.ZERO, new byte[] { OP_TRUE }));
+                    tx.addOutput(new TransactionOutput(params, tx, Coin.ZERO, new byte[] { OP_TRUE }));
+                    tx.addOutput(new TransactionOutput(params, tx, Coin.ZERO, new byte[] { OP_TRUE }));
                     lastOutput = new TransactionOutPoint(params, 1, tx.getHash());
                     hashesToSpend.add(tx.getHash());
                     block.addTransaction(tx);
@@ -1560,7 +1560,7 @@ public class FullBlockTestGenerator {
                     Transaction tx = new Transaction(params);
                     tx.addInput(new TransactionInput(params, tx, new byte[] { OP_TRUE },
                                     new TransactionOutPoint(params, 0, hashes.next())));
-                    tx.addOutput(new TransactionOutput(params, tx, BigInteger.ZERO, new byte[] { OP_TRUE }));
+                    tx.addOutput(new TransactionOutput(params, tx, Coin.ZERO, new byte[] { OP_TRUE }));
                     block.addTransaction(tx);
                 }
                 block.solve();
@@ -1586,7 +1586,7 @@ public class FullBlockTestGenerator {
                 Transaction tx = new Transaction(params);
                 tx.addInput(new TransactionInput(params, tx, new byte[] {OP_TRUE},
                             new TransactionOutPoint(params, 0, hashesToSpend.get(0))));
-                tx.addOutput(new TransactionOutput(params, tx, BigInteger.ZERO, new byte[] { OP_TRUE }));
+                tx.addOutput(new TransactionOutput(params, tx, Coin.ZERO, new byte[] { OP_TRUE }));
                 b1002.addTransaction(tx);
             }
             b1002.solve();
@@ -1602,7 +1602,7 @@ public class FullBlockTestGenerator {
                 Transaction tx = new Transaction(params);
                 tx.addInput(new TransactionInput(params, tx, new byte[] {OP_TRUE},
                             new TransactionOutPoint(params, 0, hashesToSpend.get(0))));
-                tx.addOutput(new TransactionOutput(params, tx, BigInteger.ZERO, new byte[] { OP_TRUE }));
+                tx.addOutput(new TransactionOutput(params, tx, Coin.ZERO, new byte[] { OP_TRUE }));
                 b1004.addTransaction(tx);
             }
             b1004.solve();
@@ -1620,22 +1620,22 @@ public class FullBlockTestGenerator {
 
     private byte uniquenessCounter = 0;
     private Block createNextBlock(Block baseBlock, int nextBlockHeight, TransactionOutPointWithValue prevOut,
-            BigInteger additionalCoinbaseValue) throws ScriptException {
+            Coin additionalCoinbaseValue) throws ScriptException {
         Integer height = blockToHeightMap.get(baseBlock.getHash());
         if (height != null)
             Preconditions.checkState(height == nextBlockHeight - 1);
-        BigInteger coinbaseValue = Utils.toNanoCoins(50, 0).shiftRight(nextBlockHeight / params.getSubsidyDecreaseBlockCount())
-                .add((prevOut != null ? prevOut.value.subtract(BigInteger.ONE) : BigInteger.ZERO))
-                .add(additionalCoinbaseValue == null ? BigInteger.ZERO : additionalCoinbaseValue);
+        Coin coinbaseValue = Utils.toNanoCoins(50, 0).shiftRight(nextBlockHeight / params.getSubsidyDecreaseBlockCount())
+                .add((prevOut != null ? prevOut.value.subtract(Coin.ONE) : Coin.ZERO))
+                .add(additionalCoinbaseValue == null ? Coin.ZERO : additionalCoinbaseValue);
         Block block = baseBlock.createNextBlockWithCoinbase(coinbaseOutKeyPubKey, coinbaseValue);
         if (prevOut != null) {
             Transaction t = new Transaction(params);
             // Entirely invalid scriptPubKey to ensure we aren't pre-verifying too much
-            t.addOutput(new TransactionOutput(params, t, BigInteger.valueOf(0), new byte[] {OP_PUSHDATA1 - 1 }));
-            t.addOutput(new TransactionOutput(params, t, BigInteger.valueOf(1),
+            t.addOutput(new TransactionOutput(params, t, Coin.valueOf(0), new byte[] {OP_PUSHDATA1 - 1 }));
+            t.addOutput(new TransactionOutput(params, t, Coin.valueOf(1),
                     ScriptBuilder.createOutputScript(ECKey.fromPublicOnly(coinbaseOutKeyPubKey)).getProgram()));
             // Spendable output
-            t.addOutput(new TransactionOutput(params, t, BigInteger.ZERO, new byte[] {OP_1, uniquenessCounter++}));
+            t.addOutput(new TransactionOutput(params, t, Coin.ZERO, new byte[] {OP_1, uniquenessCounter++}));
             addOnlyInputToTransaction(t, prevOut);
             block.addTransaction(t);
             block.solve();
diff --git a/core/src/test/java/com/google/bitcoin/core/PeerGroupTest.java b/core/src/test/java/com/google/bitcoin/core/PeerGroupTest.java
index 0524c8a0..49f0a1de 100644
--- a/core/src/test/java/com/google/bitcoin/core/PeerGroupTest.java
+++ b/core/src/test/java/com/google/bitcoin/core/PeerGroupTest.java
@@ -34,7 +34,6 @@ import org.junit.Test;
 import org.junit.runner.RunWith;
 import org.junit.runners.Parameterized;
 
-import java.math.BigInteger;
 import java.net.InetSocketAddress;
 import java.util.*;
 import java.util.concurrent.BlockingQueue;
@@ -179,7 +178,7 @@ public class PeerGroupTest extends TestWithPeerGroup {
         expectedPeers.add(peerOf(p2));
         assertEquals(tmp, expectedPeers);
 
-        BigInteger value = Utils.toNanoCoins(1, 0);
+        Coin value = Utils.toNanoCoins(1, 0);
         Transaction t1 = FakeTxBuilder.createFakeTx(unitTestParams, value, address);
         InventoryMessage inv = new InventoryMessage(unitTestParams);
         inv.addTransaction(t1);
diff --git a/core/src/test/java/com/google/bitcoin/core/PeerTest.java b/core/src/test/java/com/google/bitcoin/core/PeerTest.java
index fd67ce50..7d1be1b1 100644
--- a/core/src/test/java/com/google/bitcoin/core/PeerTest.java
+++ b/core/src/test/java/com/google/bitcoin/core/PeerTest.java
@@ -34,7 +34,6 @@ import org.junit.runners.Parameterized;
 import java.io.ByteArrayOutputStream;
 import java.io.IOException;
 import java.io.OutputStream;
-import java.math.BigInteger;
 import java.net.InetSocketAddress;
 import java.net.SocketException;
 import java.nio.channels.CancelledKeyException;
@@ -245,7 +244,7 @@ public class PeerTest extends TestWithNetworkConnections {
 
         peer.setDownloadData(true);
         // Make a transaction and tell the peer we have it.
-        BigInteger value = Utils.toNanoCoins(1, 0);
+        Coin value = Utils.toNanoCoins(1, 0);
         Transaction tx = createFakeTx(unitTestParams, value, address);
         InventoryMessage inv = new InventoryMessage(unitTestParams);
         InventoryItem item = new InventoryItem(InventoryItem.Type.Transaction, tx.getHash());
@@ -278,7 +277,7 @@ public class PeerTest extends TestWithNetworkConnections {
         InboundMessageQueuer writeTarget2 = connect(peer2, peerVersion);
 
         // Make a tx and advertise it to one of the peers.
-        BigInteger value = Utils.toNanoCoins(1, 0);
+        Coin value = Utils.toNanoCoins(1, 0);
         Transaction tx = createFakeTx(unitTestParams, value, this.address);
         InventoryMessage inv = new InventoryMessage(unitTestParams);
         InventoryItem item = new InventoryItem(InventoryItem.Type.Transaction, tx.getHash());
@@ -418,7 +417,7 @@ public class PeerTest extends TestWithNetworkConnections {
         Block b2 = makeSolvedTestBlock(b1);
         Transaction t = new Transaction(unitTestParams);
         t.addInput(b1.getTransactions().get(0).getOutput(0));
-        t.addOutput(new TransactionOutput(unitTestParams, t, BigInteger.ZERO, new byte[Block.MAX_BLOCK_SIZE - 1000]));
+        t.addOutput(new TransactionOutput(unitTestParams, t, Coin.ZERO, new byte[Block.MAX_BLOCK_SIZE - 1000]));
         b2.addTransaction(t);
 
         // Request the block.
@@ -659,7 +658,7 @@ public class PeerTest extends TestWithNetworkConnections {
         final Transaction[] vtx = new Transaction[1];
         wallet.addEventListener(new AbstractWalletEventListener() {
             @Override
-            public void onCoinsReceived(Wallet wallet, Transaction tx, BigInteger prevBalance, BigInteger newBalance) {
+            public void onCoinsReceived(Wallet wallet, Transaction tx, Coin prevBalance, Coin newBalance) {
                 vtx[0] = tx;
             }
         });
@@ -732,7 +731,7 @@ public class PeerTest extends TestWithNetworkConnections {
         final Transaction[] vtx = new Transaction[1];
         wallet.addEventListener(new AbstractWalletEventListener() {
             @Override
-            public void onCoinsReceived(Wallet wallet, Transaction tx, BigInteger prevBalance, BigInteger newBalance) {
+            public void onCoinsReceived(Wallet wallet, Transaction tx, Coin prevBalance, Coin newBalance) {
                 vtx[0] = tx;
             }
         });
@@ -817,7 +816,7 @@ public class PeerTest extends TestWithNetworkConnections {
     public void exceptionListener() throws Exception {
         wallet.addEventListener(new AbstractWalletEventListener() {
             @Override
-            public void onCoinsReceived(Wallet wallet, Transaction tx, BigInteger prevBalance, BigInteger newBalance) {
+            public void onCoinsReceived(Wallet wallet, Transaction tx, Coin prevBalance, Coin newBalance) {
                 throw new NullPointerException("boo!");
             }
         });
diff --git a/core/src/test/java/com/google/bitcoin/core/UtilsTest.java b/core/src/test/java/com/google/bitcoin/core/UtilsTest.java
index ed8903a5..6e5b5f56 100644
--- a/core/src/test/java/com/google/bitcoin/core/UtilsTest.java
+++ b/core/src/test/java/com/google/bitcoin/core/UtilsTest.java
@@ -16,11 +16,10 @@
 
 package com.google.bitcoin.core;
 
+import java.math.BigInteger;
 import org.junit.Assert;
 import org.junit.Test;
 
-import java.math.BigInteger;
-
 import static com.google.bitcoin.core.Utils.*;
 import static org.junit.Assert.*;
 
@@ -59,7 +58,7 @@ public class UtilsTest {
     public void testFormatting() {
         assertEquals("1.00", bitcoinValueToFriendlyString(toNanoCoins(1, 0)));
         assertEquals("1.23", bitcoinValueToFriendlyString(toNanoCoins(1, 23)));
-        assertEquals("0.001", bitcoinValueToFriendlyString(BigInteger.valueOf(COIN.longValue() / 1000)));
+        assertEquals("0.001", bitcoinValueToFriendlyString(Coin.valueOf(COIN.longValue() / 1000)));
         assertEquals("-1.23", bitcoinValueToFriendlyString(toNanoCoins(1, 23).negate()));
     }
     
@@ -76,7 +75,7 @@ public class UtilsTest {
             assertTrue(e.getMessage().contains("Value cannot be null"));
         }
 
-        assertEquals("0.0015", bitcoinValueToPlainString(BigInteger.valueOf(150000)));
+        assertEquals("0.0015", bitcoinValueToPlainString(Coin.valueOf(150000)));
         assertEquals("1.23", bitcoinValueToPlainString(toNanoCoins("1.23")));
 
         assertEquals("0.1", bitcoinValueToPlainString(toNanoCoins("0.1")));
diff --git a/core/src/test/java/com/google/bitcoin/core/WalletTest.java b/core/src/test/java/com/google/bitcoin/core/WalletTest.java
index 2bb87b83..8f4732f7 100644
--- a/core/src/test/java/com/google/bitcoin/core/WalletTest.java
+++ b/core/src/test/java/com/google/bitcoin/core/WalletTest.java
@@ -152,7 +152,7 @@ public class WalletTest extends TestWithWallet {
     private Transaction cleanupCommon(Address destination) throws Exception {
         receiveATransaction(wallet, myAddress);
 
-        BigInteger v2 = toNanoCoins(0, 50);
+        Coin v2 = toNanoCoins(0, 50);
         SendRequest req = SendRequest.to(destination, v2);
         req.fee = toNanoCoins(0, 1);
         wallet.completeTx(req);
@@ -164,7 +164,7 @@ public class WalletTest extends TestWithWallet {
 
         // At this point we have one pending and one spent
 
-        BigInteger v1 = toNanoCoins(0, 10);
+        Coin v1 = toNanoCoins(0, 10);
         Transaction t = sendMoneyToWallet(wallet, v1, myAddress, null);
         Threading.waitForUserCode();
         sendMoneyToWallet(wallet, t, null);
@@ -199,7 +199,7 @@ public class WalletTest extends TestWithWallet {
         Transaction t = cleanupCommon(destination);
 
         // Now we have another incoming pending.  Spend everything.
-        BigInteger v3 = toNanoCoins(0, 58);
+        Coin v3 = toNanoCoins(0, 58);
         SendRequest req = SendRequest.to(destination, v3);
 
         // Force selection of the incoming coin so that we can spend it
@@ -235,7 +235,7 @@ public class WalletTest extends TestWithWallet {
         receiveATransaction(wallet, toAddress);
 
         // Try to send too much and fail.
-        BigInteger vHuge = toNanoCoins(10, 0);
+        Coin vHuge = toNanoCoins(10, 0);
         Wallet.SendRequest req = Wallet.SendRequest.to(destination, vHuge);
         try {
             wallet.completeTx(req);
@@ -245,7 +245,7 @@ public class WalletTest extends TestWithWallet {
         }
 
         // Prepare to send.
-        BigInteger v2 = toNanoCoins(0, 50);
+        Coin v2 = toNanoCoins(0, 50);
         req = Wallet.SendRequest.to(destination, v2);
         req.fee = toNanoCoins(0, 1);
 
@@ -306,9 +306,9 @@ public class WalletTest extends TestWithWallet {
     }
 
     private void receiveATransaction(Wallet wallet, Address toAddress) throws Exception {
-        BigInteger v1 = Utils.toNanoCoins(1, 0);
-        final ListenableFuture<BigInteger> availFuture = wallet.getBalanceFuture(v1, Wallet.BalanceType.AVAILABLE);
-        final ListenableFuture<BigInteger> estimatedFuture = wallet.getBalanceFuture(v1, Wallet.BalanceType.ESTIMATED);
+        Coin v1 = Utils.toNanoCoins(1, 0);
+        final ListenableFuture<Coin> availFuture = wallet.getBalanceFuture(v1, Wallet.BalanceType.AVAILABLE);
+        final ListenableFuture<Coin> estimatedFuture = wallet.getBalanceFuture(v1, Wallet.BalanceType.ESTIMATED);
         assertFalse(availFuture.isDone());
         assertFalse(estimatedFuture.isDone());
         // Send some pending coins to the wallet.
@@ -316,7 +316,7 @@ public class WalletTest extends TestWithWallet {
         Threading.waitForUserCode();
         final ListenableFuture<Transaction> depthFuture = t1.getConfidence().getDepthFuture(1);
         assertFalse(depthFuture.isDone());
-        assertEquals(BigInteger.ZERO, wallet.getBalance());
+        assertEquals(Coin.ZERO, wallet.getBalance());
         assertEquals(v1, wallet.getBalance(Wallet.BalanceType.ESTIMATED));
         assertFalse(availFuture.isDone());
         // Our estimated balance has reached the requested level.
@@ -352,7 +352,7 @@ public class WalletTest extends TestWithWallet {
         final LinkedList<Transaction> txns = Lists.newLinkedList();
         wallet.addEventListener(new AbstractWalletEventListener() {
             @Override
-            public void onCoinsSent(Wallet wallet, Transaction tx, BigInteger prevBalance, BigInteger newBalance) {
+            public void onCoinsSent(Wallet wallet, Transaction tx, Coin prevBalance, Coin newBalance) {
                 txns.add(tx);
             }
         });
@@ -369,7 +369,7 @@ public class WalletTest extends TestWithWallet {
     }
 
     private void spendUnconfirmedChange(Wallet wallet, Transaction t2, KeyParameter aesKey) throws Exception {
-        BigInteger v3 = toNanoCoins(0, 49);
+        Coin v3 = toNanoCoins(0, 49);
         assertEquals(v3, wallet.getBalance());
         Wallet.SendRequest req = Wallet.SendRequest.to(new ECKey().toAddress(params), toNanoCoins(0, 48));
         req.aesKey = aesKey;
@@ -395,7 +395,7 @@ public class WalletTest extends TestWithWallet {
     // Having a test for deprecated method getFromAddress() is no evil so we suppress the warning here.
     public void customTransactionSpending() throws Exception {
         // We'll set up a wallet that receives a coin, then sends a coin of lesser value and keeps the change.
-        BigInteger v1 = Utils.toNanoCoins(3, 0);
+        Coin v1 = Utils.toNanoCoins(3, 0);
         sendMoneyToWallet(v1, AbstractBlockChain.NewBlockType.BEST_CHAIN);
         assertEquals(v1, wallet.getBalance());
         assertEquals(1, wallet.getPoolSize(WalletTransaction.Pool.UNSPENT));
@@ -403,9 +403,9 @@ public class WalletTest extends TestWithWallet {
 
         ECKey k2 = new ECKey();
         Address a2 = k2.toAddress(params);
-        BigInteger v2 = toNanoCoins(0, 50);
-        BigInteger v3 = toNanoCoins(0, 75);
-        BigInteger v4 = toNanoCoins(1, 25);
+        Coin v2 = toNanoCoins(0, 50);
+        Coin v3 = toNanoCoins(0, 75);
+        Coin v4 = toNanoCoins(1, 25);
 
         Transaction t2 = new Transaction(params);
         t2.addOutput(v2, a2);
@@ -431,13 +431,13 @@ public class WalletTest extends TestWithWallet {
     public void sideChain() throws Exception {
         // The wallet receives a coin on the main chain, then on a side chain. Balance is equal to both added together
         // as we assume the side chain tx is pending and will be included shortly.
-        BigInteger v1 = Utils.toNanoCoins(1, 0);
+        Coin v1 = Utils.toNanoCoins(1, 0);
         sendMoneyToWallet(v1, AbstractBlockChain.NewBlockType.BEST_CHAIN);
         assertEquals(v1, wallet.getBalance());
         assertEquals(1, wallet.getPoolSize(WalletTransaction.Pool.UNSPENT));
         assertEquals(1, wallet.getTransactions(true).size());
 
-        BigInteger v2 = toNanoCoins(0, 50);
+        Coin v2 = toNanoCoins(0, 50);
         sendMoneyToWallet(v2, AbstractBlockChain.NewBlockType.SIDE_CHAIN);
         assertEquals(2, wallet.getTransactions(true).size());
         assertEquals(v1, wallet.getBalance());
@@ -447,9 +447,9 @@ public class WalletTest extends TestWithWallet {
     @Test
     public void balance() throws Exception {
         // Receive 5 coins then half a coin.
-        BigInteger v1 = toNanoCoins(5, 0);
-        BigInteger v2 = toNanoCoins(0, 50);
-        BigInteger expected = toNanoCoins(5, 50);
+        Coin v1 = toNanoCoins(5, 0);
+        Coin v2 = toNanoCoins(0, 50);
+        Coin expected = toNanoCoins(5, 50);
         assertEquals(0, wallet.getTransactions(true).size());
         sendMoneyToWallet(v1, AbstractBlockChain.NewBlockType.BEST_CHAIN);
         assertEquals(1, wallet.getPoolSize(WalletTransaction.Pool.UNSPENT));
@@ -458,7 +458,7 @@ public class WalletTest extends TestWithWallet {
         assertEquals(expected, wallet.getBalance());
 
         // Now spend one coin.
-        BigInteger v3 = toNanoCoins(1, 0);
+        Coin v3 = toNanoCoins(1, 0);
         Transaction spend = wallet.createSend(new ECKey().toAddress(params), v3);
         wallet.commitTx(spend);
         assertEquals(1, wallet.getPoolSize(WalletTransaction.Pool.PENDING));
@@ -474,7 +474,7 @@ public class WalletTest extends TestWithWallet {
         wallet.receiveFromBlock(spend, b3, BlockChain.NewBlockType.BEST_CHAIN, 0);
 
         // Change is confirmed. We started with 5.50 so we should have 4.50 left.
-        BigInteger v4 = toNanoCoins(4, 50);
+        Coin v4 = toNanoCoins(4, 50);
         assertEquals(v4, wallet.getBalance(Wallet.BalanceType.AVAILABLE));
     }
 
@@ -486,12 +486,12 @@ public class WalletTest extends TestWithWallet {
     @Test
     public void blockChainCatchup() throws Exception {
         // Test that we correctly process transactions arriving from the chain, with callbacks for inbound and outbound.
-        final BigInteger bigints[] = new BigInteger[4];
+        final Coin bigints[] = new Coin[4];
         final Transaction txn[] = new Transaction[2];
         final LinkedList<Transaction> confTxns = new LinkedList<Transaction>();
         wallet.addEventListener(new AbstractWalletEventListener() {
             @Override
-            public void onCoinsReceived(Wallet wallet, Transaction tx, BigInteger prevBalance, BigInteger newBalance) {
+            public void onCoinsReceived(Wallet wallet, Transaction tx, Coin prevBalance, Coin newBalance) {
                 super.onCoinsReceived(wallet, tx, prevBalance, newBalance);
                 bigints[0] = prevBalance;
                 bigints[1] = newBalance;
@@ -499,7 +499,7 @@ public class WalletTest extends TestWithWallet {
             }
 
             @Override
-            public void onCoinsSent(Wallet wallet, Transaction tx, BigInteger prevBalance, BigInteger newBalance) {
+            public void onCoinsSent(Wallet wallet, Transaction tx, Coin prevBalance, Coin newBalance) {
                 super.onCoinsSent(wallet, tx, prevBalance, newBalance);
                 bigints[2] = prevBalance;
                 bigints[3] = newBalance;
@@ -514,13 +514,13 @@ public class WalletTest extends TestWithWallet {
         });
 
         // Receive some money.
-        BigInteger oneCoin = Utils.toNanoCoins(1, 0);
+        Coin oneCoin = Utils.toNanoCoins(1, 0);
         Transaction tx1 = sendMoneyToWallet(oneCoin, AbstractBlockChain.NewBlockType.BEST_CHAIN);
         Threading.waitForUserCode();
         assertEquals(null, txn[1]);  // onCoinsSent not called.
         assertEquals(tx1, confTxns.getFirst());   // onTransactionConfidenceChanged called
         assertEquals(txn[0].getHash(), tx1.getHash());
-        assertEquals(BigInteger.ZERO, bigints[0]);
+        assertEquals(Coin.ZERO, bigints[0]);
         assertEquals(oneCoin, bigints[1]);
         assertEquals(TransactionConfidence.ConfidenceType.BUILDING, tx1.getConfidence().getConfidenceType());
         assertEquals(1, tx1.getConfidence().getAppearedAtChainHeight());
@@ -555,7 +555,7 @@ public class WalletTest extends TestWithWallet {
 
     @Test
     public void balances() throws Exception {
-        BigInteger nanos = Utils.toNanoCoins(1, 0);
+        Coin nanos = Utils.toNanoCoins(1, 0);
         Transaction tx1 = sendMoneyToWallet(nanos, AbstractBlockChain.NewBlockType.BEST_CHAIN);
         assertEquals(nanos, tx1.getValueSentToMe(wallet, true));
         // Send 0.10 to somebody else.
@@ -563,7 +563,7 @@ public class WalletTest extends TestWithWallet {
         // Reserialize.
         Transaction send2 = new Transaction(params, send1.bitcoinSerialize());
         assertEquals(nanos, send2.getValueSentFromMe(wallet));
-        assertEquals(BigInteger.ZERO.subtract(toNanoCoins(0, 10)), send2.getValue(wallet));
+        assertEquals(Coin.ZERO.subtract(toNanoCoins(0, 10)), send2.getValue(wallet));
     }
 
     @Test
@@ -640,11 +640,11 @@ public class WalletTest extends TestWithWallet {
     public void bounce() throws Exception {
         // This test covers bug 64 (False double spends). Check that if we create a spend and it's immediately sent
         // back to us, this isn't considered as a double spend.
-        BigInteger coin1 = Utils.toNanoCoins(1, 0);
+        Coin coin1 = Utils.toNanoCoins(1, 0);
         sendMoneyToWallet(coin1, AbstractBlockChain.NewBlockType.BEST_CHAIN);
         // Send half to some other guy. Sending only half then waiting for a confirm is important to ensure the tx is
         // in the unspent pool, not pending or spent.
-        BigInteger coinHalf = Utils.toNanoCoins(0, 50);
+        Coin coinHalf = Utils.toNanoCoins(0, 50);
         assertEquals(1, wallet.getPoolSize(WalletTransaction.Pool.UNSPENT));
         assertEquals(1, wallet.getTransactions(true).size());
         Address someOtherGuy = new ECKey().toAddress(params);
@@ -675,7 +675,7 @@ public class WalletTest extends TestWithWallet {
         send2 = new Transaction(params, send2.bitcoinSerialize());
         // Broadcast send1, it's now pending.
         wallet.commitTx(send1);
-        assertEquals(BigInteger.ZERO, wallet.getBalance());
+        assertEquals(Coin.ZERO, wallet.getBalance());
         // Receive a block that overrides the send1 using send2.
         sendMoneyToWallet(send2, AbstractBlockChain.NewBlockType.BEST_CHAIN);
         // send1 got rolled back and replaced with a smaller send that only used one of our received coins, thus ...
@@ -691,8 +691,8 @@ public class WalletTest extends TestWithWallet {
         // This can (and has!) happened when a wallet is cloned between devices, and both devices decide to make the
         // same spend simultaneously - for example due a re-keying operation. It can also happen if there are malicious
         // nodes in the P2P network that are mutating transactions on the fly as occurred during Feb 2014.
-        final BigInteger value = Utils.toNanoCoins(1, 0);
-        final BigInteger value2 = Utils.toNanoCoins(2, 0);
+        final Coin value = Utils.toNanoCoins(1, 0);
+        final Coin value2 = Utils.toNanoCoins(2, 0);
         // Give us three coins and make sure we have some change.
         sendMoneyToWallet(value.add(value2), AbstractBlockChain.NewBlockType.BEST_CHAIN);
         final Address address = new ECKey().toAddress(params);
@@ -707,7 +707,7 @@ public class WalletTest extends TestWithWallet {
         // Now spend the change. This transaction should die permanently when the mutant appears in the chain.
         Transaction send3 = checkNotNull(wallet.createSend(address, value));
         wallet.commitTx(send3);
-        assertEquals(BigInteger.ZERO, wallet.getBalance());
+        assertEquals(Coin.ZERO, wallet.getBalance());
         final LinkedList<Transaction> dead = new LinkedList<Transaction>();
         final TransactionConfidence.Listener listener = new TransactionConfidence.Listener() {
             @Override
@@ -758,7 +758,7 @@ public class WalletTest extends TestWithWallet {
         });
 
         // Receive 1 BTC.
-        BigInteger nanos = Utils.toNanoCoins(1, 0);
+        Coin nanos = Utils.toNanoCoins(1, 0);
         sendMoneyToWallet(nanos, AbstractBlockChain.NewBlockType.BEST_CHAIN);
         Transaction received = wallet.getTransactions(false).iterator().next();
         // Create a send to a merchant.
@@ -794,7 +794,7 @@ public class WalletTest extends TestWithWallet {
     @Test
     public void pending1() throws Exception {
         // Check that if we receive a pending transaction that is then confirmed, we are notified as appropriate.
-        final BigInteger nanos = Utils.toNanoCoins(1, 0);
+        final Coin nanos = Utils.toNanoCoins(1, 0);
         final Transaction t1 = createFakeTx(params, nanos, myAddress);
 
         // First one is "called" second is "pending".
@@ -803,11 +803,11 @@ public class WalletTest extends TestWithWallet {
         final int[] walletChanged = new int[1];
         wallet.addEventListener(new AbstractWalletEventListener() {
             @Override
-            public void onCoinsReceived(Wallet wallet, Transaction tx, BigInteger prevBalance, BigInteger newBalance) {
+            public void onCoinsReceived(Wallet wallet, Transaction tx, Coin prevBalance, Coin newBalance) {
                 // Check we got the expected transaction.
                 assertEquals(tx, t1);
                 // Check that it's considered to be pending inclusion in the block chain.
-                assertEquals(prevBalance, BigInteger.ZERO);
+                assertEquals(prevBalance, Coin.ZERO);
                 assertEquals(newBalance, nanos);
                 flags[0] = true;
                 flags[1] = tx.isPending();
@@ -867,21 +867,21 @@ public class WalletTest extends TestWithWallet {
     public void pending2() throws Exception {
         // Check that if we receive a pending tx we did not send, it updates our spent flags correctly.
         final Transaction txn[] = new Transaction[1];
-        final BigInteger bigints[] = new BigInteger[2];
+        final Coin bigints[] = new Coin[2];
         wallet.addEventListener(new AbstractWalletEventListener() {
             @Override
-            public void onCoinsSent(Wallet wallet, Transaction tx, BigInteger prevBalance, BigInteger newBalance) {
+            public void onCoinsSent(Wallet wallet, Transaction tx, Coin prevBalance, Coin newBalance) {
                 txn[0] = tx;
                 bigints[0] = prevBalance;
                 bigints[1] = newBalance;
             }
         });
         // Receive some coins.
-        BigInteger nanos = Utils.toNanoCoins(1, 0);
+        Coin nanos = Utils.toNanoCoins(1, 0);
         sendMoneyToWallet(nanos, AbstractBlockChain.NewBlockType.BEST_CHAIN);
         // Create a spend with them, but don't commit it (ie it's from somewhere else but using our keys). This TX
         // will have change as we don't spend our entire balance.
-        BigInteger halfNanos = Utils.toNanoCoins(0, 50);
+        Coin halfNanos = Utils.toNanoCoins(0, 50);
         Transaction t2 = wallet.createSend(new ECKey().toAddress(params), halfNanos);
         // Now receive it as pending.
         if (wallet.isPendingTransactionRelevant(t2))
@@ -900,7 +900,7 @@ public class WalletTest extends TestWithWallet {
         // Check that if we receive a pending tx, and it's overridden by a double spend from the main chain, we
         // are notified that it's dead. This should work even if the pending tx inputs are NOT ours, ie, they don't
         // connect to anything.
-        BigInteger nanos = Utils.toNanoCoins(1, 0);
+        Coin nanos = Utils.toNanoCoins(1, 0);
 
         // Create two transactions that share the same input tx.
         Address badGuy = new ECKey().toAddress(params);
@@ -918,7 +918,7 @@ public class WalletTest extends TestWithWallet {
 
         final Transaction[] called = new Transaction[2];
         wallet.addEventListener(new AbstractWalletEventListener() {
-            public void onCoinsReceived(Wallet wallet, Transaction tx, BigInteger prevBalance, BigInteger newBalance) {
+            public void onCoinsReceived(Wallet wallet, Transaction tx, Coin prevBalance, Coin newBalance) {
                 called[0] = tx;
             }
 
@@ -933,7 +933,7 @@ public class WalletTest extends TestWithWallet {
             }
         });
 
-        assertEquals(BigInteger.ZERO, wallet.getBalance());
+        assertEquals(Coin.ZERO, wallet.getBalance());
         if (wallet.isPendingTransactionRelevant(t1))
             wallet.receivePending(t1, null);
         Threading.waitForUserCode();
@@ -943,7 +943,7 @@ public class WalletTest extends TestWithWallet {
         called[0] = called[1] = null;
         sendMoneyToWallet(t2, AbstractBlockChain.NewBlockType.BEST_CHAIN);
         Threading.waitForUserCode();
-        assertEquals(BigInteger.ZERO, wallet.getBalance());
+        assertEquals(Coin.ZERO, wallet.getBalance());
         assertEquals(t1, called[0]); // dead
         assertEquals(t2, called[1]); // replacement
     }
@@ -1021,8 +1021,8 @@ public class WalletTest extends TestWithWallet {
         // Test that a spend to the same wallet is dealt with correctly.
         // It should appear in the wallet and confirm.
         // This is a bit of a silly thing to do in the real world as all it does is burn a fee but it is perfectly valid.
-        BigInteger coin1 = Utils.toNanoCoins(1, 0);
-        BigInteger coinHalf = Utils.toNanoCoins(0, 50);
+        Coin coin1 = Utils.toNanoCoins(1, 0);
+        Coin coinHalf = Utils.toNanoCoins(0, 50);
         // Start by giving us 1 coin.
         sendMoneyToWallet(coin1, AbstractBlockChain.NewBlockType.BEST_CHAIN);
         // Send half to ourselves. We should then have a balance available to spend of zero.
@@ -1031,7 +1031,7 @@ public class WalletTest extends TestWithWallet {
         Transaction outbound1 = wallet.createSend(myAddress, coinHalf);
         wallet.commitTx(outbound1);
         // We should have a zero available balance before the next block.
-        assertEquals(BigInteger.ZERO, wallet.getBalance());
+        assertEquals(Coin.ZERO, wallet.getBalance());
         sendMoneyToWallet(outbound1, AbstractBlockChain.NewBlockType.BEST_CHAIN);
         // We should have a balance of 1 BTC after the block is received.
         assertEquals(coin1, wallet.getBalance());
@@ -1039,9 +1039,9 @@ public class WalletTest extends TestWithWallet {
 
     @Test
     public void lastBlockSeen() throws Exception {
-        BigInteger v1 = toNanoCoins(5, 0);
-        BigInteger v2 = toNanoCoins(0, 50);
-        BigInteger v3 = toNanoCoins(0, 25);
+        Coin v1 = toNanoCoins(5, 0);
+        Coin v2 = toNanoCoins(0, 50);
+        Coin v3 = toNanoCoins(0, 25);
         Transaction t1 = createFakeTx(params, v1, myAddress);
         Transaction t2 = createFakeTx(params, v2, myAddress);
         Transaction t3 = createFakeTx(params, v3, myAddress);
@@ -1072,13 +1072,13 @@ public class WalletTest extends TestWithWallet {
     public void pubkeyOnlyScripts() throws Exception {
         // Verify that we support outputs like OP_PUBKEY and the corresponding inputs.
         ECKey key1 = wallet.freshReceiveKey();
-        BigInteger value = toNanoCoins(5, 0);
+        Coin value = toNanoCoins(5, 0);
         Transaction t1 = createFakeTx(params, value, key1);
         if (wallet.isPendingTransactionRelevant(t1))
             wallet.receivePending(t1, null);
         // TX should have been seen as relevant.
         assertEquals(value, wallet.getBalance(Wallet.BalanceType.ESTIMATED));
-        assertEquals(BigInteger.ZERO, wallet.getBalance(Wallet.BalanceType.AVAILABLE));
+        assertEquals(Coin.ZERO, wallet.getBalance(Wallet.BalanceType.AVAILABLE));
         Block b1 = createFakeBlock(blockStore, t1).block;
         chain.add(b1);
         // TX should have been seen as relevant, extracted and processed.
@@ -1114,7 +1114,7 @@ public class WalletTest extends TestWithWallet {
         ECKey key = new ECKey();
         Address watchedAddress = key.toAddress(params);
         wallet.addWatchedAddress(watchedAddress);
-        BigInteger value = toNanoCoins(5, 0);
+        Coin value = toNanoCoins(5, 0);
         Transaction t1 = createFakeTx(params, value, watchedAddress);
         assertTrue(wallet.isPendingTransactionRelevant(t1));
     }
@@ -1127,7 +1127,7 @@ public class WalletTest extends TestWithWallet {
         Transaction t1 = createFakeTx(params, CENT, watchedAddress);
         StoredBlock b3 = createFakeBlock(blockStore, t1).storedBlock;
         wallet.receiveFromBlock(t1, b3, BlockChain.NewBlockType.BEST_CHAIN, 0);
-        assertEquals(BigInteger.ZERO, wallet.getBalance());
+        assertEquals(Coin.ZERO, wallet.getBalance());
         assertEquals(CENT, wallet.getWatchedBalance());
 
         // We can't spend watched balances
@@ -1273,11 +1273,11 @@ public class WalletTest extends TestWithWallet {
     @Test
     public void spendOutputFromPendingTransaction() throws Exception {
         // We'll set up a wallet that receives a coin, then sends a coin of lesser value and keeps the change.
-        BigInteger v1 = Utils.toNanoCoins(1, 0);
+        Coin v1 = Utils.toNanoCoins(1, 0);
         sendMoneyToWallet(v1, AbstractBlockChain.NewBlockType.BEST_CHAIN);
         // First create our current transaction
         ECKey k2 = wallet.freshReceiveKey();
-        BigInteger v2 = toNanoCoins(0, 50);
+        Coin v2 = toNanoCoins(0, 50);
         Transaction t2 = new Transaction(params);
         TransactionOutput o2 = new TransactionOutput(params, t2, v2, k2.toAddress(params));
         t2.addOutput(o2);
@@ -1293,7 +1293,7 @@ public class WalletTest extends TestWithWallet {
 
         // Now try to the spend the output.
         ECKey k3 = new ECKey();
-        BigInteger v3 = toNanoCoins(0, 25);
+        Coin v3 = toNanoCoins(0, 25);
         Transaction t3 = new Transaction(params);
         t3.addOutput(v3, k3.toAddress(params));
         t3.addInput(o2);
@@ -1314,7 +1314,7 @@ public class WalletTest extends TestWithWallet {
         // Check that if a pending transaction spends outputs of chain-included transactions, we mark them as spent.
         // See bug 345. This can happen if there is a pending transaction floating around and then you replay the
         // chain without emptying the memory pool (or refilling it from a peer).
-        BigInteger value = Utils.toNanoCoins(1, 0);
+        Coin value = Utils.toNanoCoins(1, 0);
         Transaction tx1 = createFakeTx(params, value, myAddress);
         Transaction tx2 = new Transaction(params);
         tx2.addInput(tx1.getOutput(0));
@@ -1325,7 +1325,7 @@ public class WalletTest extends TestWithWallet {
         BlockPair bp = createFakeBlock(blockStore, tx1);
         wallet.receiveFromBlock(tx1, bp.storedBlock, AbstractBlockChain.NewBlockType.BEST_CHAIN, 0);
         wallet.notifyNewBestBlock(bp.storedBlock);
-        assertEquals(BigInteger.ZERO, wallet.getBalance());
+        assertEquals(Coin.ZERO, wallet.getBalance());
         assertEquals(1, wallet.getPoolSize(Pool.SPENT));
         assertEquals(1, wallet.getPoolSize(Pool.PENDING));
         assertEquals(0, wallet.getPoolSize(Pool.UNSPENT));
@@ -1461,7 +1461,7 @@ public class WalletTest extends TestWithWallet {
         Transaction tx = new Transaction(params);
         byte[] bits = new byte[20];
         new Random().nextBytes(bits);
-        BigInteger v = Utils.toNanoCoins(0, 1);
+        Coin v = Utils.toNanoCoins(0, 1);
         // 3100 outputs to a random address.
         for (int i = 0; i < 3100; i++) {
             tx.addOutput(v, new Address(params, bits));
@@ -1481,26 +1481,26 @@ public class WalletTest extends TestWithWallet {
 
         // Generate a few outputs to us that are far too small to spend reasonably
         StoredBlock block = new StoredBlock(makeSolvedTestBlock(blockStore, notMyAddr), BigInteger.ONE, 1);
-        Transaction tx1 = createFakeTx(params, BigInteger.ONE, myAddress);
+        Transaction tx1 = createFakeTx(params, Coin.ONE, myAddress);
         wallet.receiveFromBlock(tx1, block, AbstractBlockChain.NewBlockType.BEST_CHAIN, 0);
-        Transaction tx2 = createFakeTx(params, BigInteger.ONE, myAddress);
+        Transaction tx2 = createFakeTx(params, Coin.ONE, myAddress);
         assertTrue(!tx1.getHash().equals(tx2.getHash()));
         wallet.receiveFromBlock(tx2, block, AbstractBlockChain.NewBlockType.BEST_CHAIN, 1);
-        Transaction tx3 = createFakeTx(params, BigInteger.TEN, myAddress);
+        Transaction tx3 = createFakeTx(params, Coin.TEN, myAddress);
         wallet.receiveFromBlock(tx3, block, AbstractBlockChain.NewBlockType.BEST_CHAIN, 2);
 
         // Not allowed to send dust.
         try {
-            wallet.createSend(notMyAddr, BigInteger.ONE);
+            wallet.createSend(notMyAddr, Coin.ONE);
             fail();
         } catch (Wallet.DustySendRequested e) {
             // Expected.
         }
         // Spend it all without fee enforcement
-        SendRequest req = SendRequest.to(notMyAddr, BigInteger.TEN.add(BigInteger.ONE.add(BigInteger.ONE)));
+        SendRequest req = SendRequest.to(notMyAddr, Coin.TEN.add(Coin.ONE.add(Coin.ONE)));
         req.ensureMinRequiredFee = false;
         assertNotNull(wallet.sendCoinsOffline(req));
-        assertEquals(BigInteger.ZERO, wallet.getBalance());
+        assertEquals(Coin.ZERO, wallet.getBalance());
 
         // Add some reasonable-sized outputs
         block = new StoredBlock(makeSolvedTestBlock(blockStore, notMyAddr), BigInteger.ONE, 1);
@@ -1508,7 +1508,7 @@ public class WalletTest extends TestWithWallet {
         wallet.receiveFromBlock(tx4, block, AbstractBlockChain.NewBlockType.BEST_CHAIN, 0);
 
         // Simple test to make sure if we have an ouput < 0.01 we get a fee
-        Transaction spend1 = wallet.createSend(notMyAddr, CENT.subtract(BigInteger.ONE));
+        Transaction spend1 = wallet.createSend(notMyAddr, CENT.subtract(Coin.ONE));
         assertEquals(2, spend1.getOutputs().size());
         // We optimize for priority, so the output selected should be the largest one.
         // We should have paid the default minfee.
@@ -1522,19 +1522,19 @@ public class WalletTest extends TestWithWallet {
         assertEquals(Utils.COIN, spend2.getOutput(0).getValue().add(spend2.getOutput(1).getValue()));
 
         // ...but not more fee than what we request
-        SendRequest request3 = SendRequest.to(notMyAddr, CENT.subtract(BigInteger.ONE));
-        request3.fee = Transaction.REFERENCE_DEFAULT_MIN_TX_FEE.add(BigInteger.ONE);
+        SendRequest request3 = SendRequest.to(notMyAddr, CENT.subtract(Coin.ONE));
+        request3.fee = Transaction.REFERENCE_DEFAULT_MIN_TX_FEE.add(Coin.ONE);
         wallet.completeTx(request3);
-        assertEquals(Transaction.REFERENCE_DEFAULT_MIN_TX_FEE.add(BigInteger.ONE), request3.fee);
+        assertEquals(Transaction.REFERENCE_DEFAULT_MIN_TX_FEE.add(Coin.ONE), request3.fee);
         Transaction spend3 = request3.tx;
         assertEquals(2, spend3.getOutputs().size());
         // We optimize for priority, so the output selected should be the largest one.
         assertEquals(spend3.getOutput(0).getValue().add(spend3.getOutput(1).getValue()),
-                Utils.COIN.subtract(Transaction.REFERENCE_DEFAULT_MIN_TX_FEE.add(BigInteger.ONE)));
+                Utils.COIN.subtract(Transaction.REFERENCE_DEFAULT_MIN_TX_FEE.add(Coin.ONE)));
 
         // ...unless we need it
-        SendRequest request4 = SendRequest.to(notMyAddr, CENT.subtract(BigInteger.ONE));
-        request4.fee = Transaction.REFERENCE_DEFAULT_MIN_TX_FEE.subtract(BigInteger.ONE);
+        SendRequest request4 = SendRequest.to(notMyAddr, CENT.subtract(Coin.ONE));
+        request4.fee = Transaction.REFERENCE_DEFAULT_MIN_TX_FEE.subtract(Coin.ONE);
         wallet.completeTx(request4);
         assertEquals(Transaction.REFERENCE_DEFAULT_MIN_TX_FEE, request4.fee);
         Transaction spend4 = request4.tx;
@@ -1543,7 +1543,7 @@ public class WalletTest extends TestWithWallet {
         assertEquals(spend4.getOutput(0).getValue().add(spend4.getOutput(1).getValue()),
                 Utils.COIN.subtract(Transaction.REFERENCE_DEFAULT_MIN_TX_FEE));
 
-        SendRequest request5 = SendRequest.to(notMyAddr, Utils.COIN.subtract(CENT.subtract(BigInteger.ONE)));
+        SendRequest request5 = SendRequest.to(notMyAddr, Utils.COIN.subtract(CENT.subtract(Coin.ONE)));
         wallet.completeTx(request5);
         assertEquals(Transaction.REFERENCE_DEFAULT_MIN_TX_FEE, request5.fee);
         Transaction spend5 = request5.tx;
@@ -1555,15 +1555,15 @@ public class WalletTest extends TestWithWallet {
 
         SendRequest request6 = SendRequest.to(notMyAddr, Utils.COIN.subtract(CENT));
         wallet.completeTx(request6);
-        assertEquals(BigInteger.ZERO, request6.fee);
+        assertEquals(Coin.ZERO, request6.fee);
         Transaction spend6 = request6.tx;
         // ...but not if change output == 0.01
         assertEquals(2, spend6.getOutputs().size());
         // We optimize for priority, so the output selected should be the largest one
         assertEquals(Utils.COIN, spend6.getOutput(0).getValue().add(spend6.getOutput(1).getValue()));
 
-        SendRequest request7 = SendRequest.to(notMyAddr, Utils.COIN.subtract(CENT.subtract(BigInteger.valueOf(2)).multiply(BigInteger.valueOf(2))));
-        request7.tx.addOutput(CENT.subtract(BigInteger.ONE), notMyAddr);
+        SendRequest request7 = SendRequest.to(notMyAddr, Utils.COIN.subtract(CENT.subtract(Coin.valueOf(2)).multiply(Coin.valueOf(2))));
+        request7.tx.addOutput(CENT.subtract(Coin.ONE), notMyAddr);
         wallet.completeTx(request7);
         assertEquals(Transaction.REFERENCE_DEFAULT_MIN_TX_FEE, request7.fee);
         Transaction spend7 = request7.tx;
@@ -1594,7 +1594,7 @@ public class WalletTest extends TestWithWallet {
                 Utils.COIN.subtract(Transaction.REFERENCE_DEFAULT_MIN_TX_FEE.add(Transaction.MIN_NONDUST_OUTPUT)));
 
         SendRequest request10 = SendRequest.to(notMyAddr, Utils.COIN.subtract(
-                Transaction.REFERENCE_DEFAULT_MIN_TX_FEE.add(Transaction.MIN_NONDUST_OUTPUT).add(BigInteger.ONE)));
+                Transaction.REFERENCE_DEFAULT_MIN_TX_FEE.add(Transaction.MIN_NONDUST_OUTPUT).add(Coin.ONE)));
         wallet.completeTx(request10);
         assertEquals(Transaction.REFERENCE_DEFAULT_MIN_TX_FEE, request10.fee);
         Transaction spend10 = request10.tx;
@@ -1605,16 +1605,16 @@ public class WalletTest extends TestWithWallet {
                 Utils.COIN.subtract(Transaction.REFERENCE_DEFAULT_MIN_TX_FEE));
 
         SendRequest request11 = SendRequest.to(notMyAddr, Utils.COIN.subtract(
-                Transaction.REFERENCE_DEFAULT_MIN_TX_FEE.add(Transaction.MIN_NONDUST_OUTPUT).add(BigInteger.valueOf(2))));
-        request11.fee = Transaction.REFERENCE_DEFAULT_MIN_TX_FEE.add(BigInteger.ONE);
+                Transaction.REFERENCE_DEFAULT_MIN_TX_FEE.add(Transaction.MIN_NONDUST_OUTPUT).add(Coin.valueOf(2))));
+        request11.fee = Transaction.REFERENCE_DEFAULT_MIN_TX_FEE.add(Coin.ONE);
         wallet.completeTx(request11);
-        assertEquals(Transaction.REFERENCE_DEFAULT_MIN_TX_FEE.add(BigInteger.ONE), request11.fee);
+        assertEquals(Transaction.REFERENCE_DEFAULT_MIN_TX_FEE.add(Coin.ONE), request11.fee);
         Transaction spend11 = request11.tx;
         // ...of course fee should be min(request.fee, MIN_TX_FEE) so we should get MIN_TX_FEE.add(ONE) here
         assertEquals(2, spend11.getOutputs().size());
         // We optimize for priority, so the output selected should be the largest one.
         assertEquals(spend11.getOutput(0).getValue().add(spend11.getOutput(1).getValue()),
-                Utils.COIN.subtract(Transaction.REFERENCE_DEFAULT_MIN_TX_FEE.add(BigInteger.ONE)));
+                Utils.COIN.subtract(Transaction.REFERENCE_DEFAULT_MIN_TX_FEE.add(Coin.ONE)));
 
         // Remove the coin from our wallet
         wallet.commitTx(spend11);
@@ -1658,30 +1658,30 @@ public class WalletTest extends TestWithWallet {
         for (int i = 0; i < 29; i++)
             request15.tx.addOutput(CENT, notMyAddr);
         assertTrue(request15.tx.bitcoinSerialize().length > 1000);
-        request15.feePerKb = BigInteger.ONE;
+        request15.feePerKb = Coin.ONE;
         wallet.completeTx(request15);
-        assertEquals(BigInteger.valueOf(2), request15.fee);
+        assertEquals(Coin.valueOf(2), request15.fee);
         Transaction spend15 = request15.tx;
         // If a transaction is over 1kb, 2 satoshis should be added.
         assertEquals(31, spend15.getOutputs().size());
         // We optimize for priority, so the output selected should be the largest one
-        BigInteger outValue15 = BigInteger.ZERO;
+        Coin outValue15 = Coin.ZERO;
         for (TransactionOutput out : spend15.getOutputs())
             outValue15 = outValue15.add(out.getValue());
-        assertEquals(Utils.COIN.subtract(BigInteger.valueOf(2)), outValue15);
+        assertEquals(Utils.COIN.subtract(Coin.valueOf(2)), outValue15);
 
         SendRequest request16 = SendRequest.to(notMyAddr, CENT);
-        request16.feePerKb = BigInteger.ZERO;
+        request16.feePerKb = Coin.ZERO;
         for (int i = 0; i < 29; i++)
             request16.tx.addOutput(CENT, notMyAddr);
         assertTrue(request16.tx.bitcoinSerialize().length > 1000);
         wallet.completeTx(request16);
         // Of course the fee shouldn't be added if feePerKb == 0
-        assertEquals(BigInteger.ZERO, request16.fee);
+        assertEquals(Coin.ZERO, request16.fee);
         Transaction spend16 = request16.tx;
         assertEquals(31, spend16.getOutputs().size());
         // We optimize for priority, so the output selected should be the largest one
-        BigInteger outValue16 = BigInteger.ZERO;
+        Coin outValue16 = Coin.ZERO;
         for (TransactionOutput out : spend16.getOutputs())
             outValue16 = outValue16.add(out.getValue());
         assertEquals(Utils.COIN, outValue16);
@@ -1691,9 +1691,9 @@ public class WalletTest extends TestWithWallet {
         for (int i = 0; i < 22; i++)
             request17.tx.addOutput(CENT, notMyAddr);
         request17.tx.addOutput(new TransactionOutput(params, request17.tx, CENT, new byte[15]));
-        request17.feePerKb = BigInteger.ONE;
+        request17.feePerKb = Coin.ONE;
         wallet.completeTx(request17);
-        assertEquals(BigInteger.ONE, request17.fee);
+        assertEquals(Coin.ONE, request17.fee);
         assertEquals(1, request17.tx.getInputs().size());
         // Calculate its max length to make sure it is indeed 999
         int theoreticalMaxLength17 = request17.tx.bitcoinSerialize().length + myKey.getPubKey().length + 75;
@@ -1709,19 +1709,19 @@ public class WalletTest extends TestWithWallet {
         // Now check that it got a fee of 1 since its max size is 999 (1kb).
         assertEquals(25, spend17.getOutputs().size());
         // We optimize for priority, so the output selected should be the largest one
-        BigInteger outValue17 = BigInteger.ZERO;
+        Coin outValue17 = Coin.ZERO;
         for (TransactionOutput out : spend17.getOutputs())
             outValue17 = outValue17.add(out.getValue());
-        assertEquals(Utils.COIN.subtract(BigInteger.ONE), outValue17);
+        assertEquals(Utils.COIN.subtract(Coin.ONE), outValue17);
 
         // Create a transaction who's max size could be up to 1001 (if signatures were maximum size)
         SendRequest request18 = SendRequest.to(notMyAddr, CENT);
         for (int i = 0; i < 22; i++)
             request18.tx.addOutput(CENT, notMyAddr);
         request18.tx.addOutput(new TransactionOutput(params, request18.tx, CENT, new byte[17]));
-        request18.feePerKb = BigInteger.ONE;
+        request18.feePerKb = Coin.ONE;
         wallet.completeTx(request18);
-        assertEquals(BigInteger.valueOf(2), request18.fee);
+        assertEquals(Coin.valueOf(2), request18.fee);
         assertEquals(1, request18.tx.getInputs().size());
         // Calculate its max length to make sure it is indeed 1001
         Transaction spend18 = request18.tx;
@@ -1735,31 +1735,31 @@ public class WalletTest extends TestWithWallet {
         // Now check that it did get a fee since its max size is 1000
         assertEquals(25, spend18.getOutputs().size());
         // We optimize for priority, so the output selected should be the largest one
-        BigInteger outValue18 = BigInteger.ZERO;
+        Coin outValue18 = Coin.ZERO;
         for (TransactionOutput out : spend18.getOutputs())
             outValue18 = outValue18.add(out.getValue());
-        assertEquals(outValue18, Utils.COIN.subtract(BigInteger.valueOf(2)));
+        assertEquals(outValue18, Utils.COIN.subtract(Coin.valueOf(2)));
 
         // Now create a transaction that will spend COIN + fee, which makes it require both inputs
         assertEquals(wallet.getBalance(), CENT.add(Utils.COIN));
         SendRequest request19 = SendRequest.to(notMyAddr, CENT);
-        request19.feePerKb = BigInteger.ZERO;
+        request19.feePerKb = Coin.ZERO;
         for (int i = 0; i < 99; i++)
             request19.tx.addOutput(CENT, notMyAddr);
         // If we send now, we shouldn't need a fee and should only have to spend our COIN
         wallet.completeTx(request19);
-        assertEquals(BigInteger.ZERO, request19.fee);
+        assertEquals(Coin.ZERO, request19.fee);
         assertEquals(1, request19.tx.getInputs().size());
         assertEquals(100, request19.tx.getOutputs().size());
         // Now reset request19 and give it a fee per kb
         request19.tx.clearInputs();
         request19 = SendRequest.forTx(request19.tx);
-        request19.feePerKb = BigInteger.ONE;
+        request19.feePerKb = Coin.ONE;
         request19.shuffleOutputs = false;
         wallet.completeTx(request19);
         assertEquals(Transaction.REFERENCE_DEFAULT_MIN_TX_FEE, request19.fee);
         assertEquals(2, request19.tx.getInputs().size());
-        BigInteger outValue19 = BigInteger.ZERO;
+        Coin outValue19 = Coin.ZERO;
         for (TransactionOutput out : request19.tx.getOutputs())
             outValue19 = outValue19.add(out.getValue());
         // But now our change output is CENT-minfee, so we have to pay min fee
@@ -1768,12 +1768,12 @@ public class WalletTest extends TestWithWallet {
 
         // Create another transaction that will spend COIN + fee, which makes it require both inputs
         SendRequest request20 = SendRequest.to(notMyAddr, CENT);
-        request20.feePerKb = BigInteger.ZERO;
+        request20.feePerKb = Coin.ZERO;
         for (int i = 0; i < 99; i++)
             request20.tx.addOutput(CENT, notMyAddr);
         // If we send now, we shouldn't have a fee and should only have to spend our COIN
         wallet.completeTx(request20);
-        assertEquals(BigInteger.ZERO, request20.fee);
+        assertEquals(Coin.ZERO, request20.fee);
         assertEquals(1, request20.tx.getInputs().size());
         assertEquals(100, request20.tx.getOutputs().size());
         // Now reset request19 and give it a fee per kb
@@ -1782,18 +1782,18 @@ public class WalletTest extends TestWithWallet {
         request20.feePerKb = Transaction.REFERENCE_DEFAULT_MIN_TX_FEE;
         wallet.completeTx(request20);
         // 4kb tx.
-        assertEquals(Transaction.REFERENCE_DEFAULT_MIN_TX_FEE.multiply(BigInteger.valueOf(4)), request20.fee);
+        assertEquals(Transaction.REFERENCE_DEFAULT_MIN_TX_FEE.multiply(Coin.valueOf(4)), request20.fee);
         assertEquals(2, request20.tx.getInputs().size());
-        BigInteger outValue20 = BigInteger.ZERO;
+        Coin outValue20 = Coin.ZERO;
         for (TransactionOutput out : request20.tx.getOutputs())
             outValue20 = outValue20.add(out.getValue());
         // This time the fee we wanted to pay was more, so that should be what we paid
-        assertEquals(outValue20, Utils.COIN.add(CENT).subtract(Transaction.REFERENCE_DEFAULT_MIN_TX_FEE.multiply(BigInteger.valueOf(4))));
+        assertEquals(outValue20, Utils.COIN.add(CENT).subtract(Transaction.REFERENCE_DEFAULT_MIN_TX_FEE.multiply(Coin.valueOf(4))));
 
         // Same as request 19, but make the change 0 (so it doesnt force fee) and make us require min fee as a
         // result of an output < CENT.
         SendRequest request21 = SendRequest.to(notMyAddr, CENT);
-        request21.feePerKb = BigInteger.ZERO;
+        request21.feePerKb = Coin.ZERO;
         for (int i = 0; i < 99; i++)
             request21.tx.addOutput(CENT, notMyAddr);
         request21.tx.addOutput(CENT.subtract(Transaction.REFERENCE_DEFAULT_MIN_TX_FEE), notMyAddr);
@@ -1801,7 +1801,7 @@ public class WalletTest extends TestWithWallet {
         wallet.completeTx(request21);
         assertEquals(Transaction.REFERENCE_DEFAULT_MIN_TX_FEE, request21.fee);
         assertEquals(2, request21.tx.getInputs().size());
-        BigInteger outValue21 = BigInteger.ZERO;
+        Coin outValue21 = Coin.ZERO;
         for (TransactionOutput out : request21.tx.getOutputs())
             outValue21 = outValue21.add(out.getValue());
         assertEquals(outValue21, Utils.COIN.add(CENT).subtract(Transaction.REFERENCE_DEFAULT_MIN_TX_FEE));
@@ -1809,30 +1809,30 @@ public class WalletTest extends TestWithWallet {
         // Test feePerKb when we aren't using ensureMinRequiredFee
         // Same as request 19
         SendRequest request25 = SendRequest.to(notMyAddr, CENT);
-        request25.feePerKb = BigInteger.ZERO;
+        request25.feePerKb = Coin.ZERO;
         for (int i = 0; i < 70; i++)
             request25.tx.addOutput(CENT, notMyAddr);
         // If we send now, we shouldn't need a fee and should only have to spend our COIN
         wallet.completeTx(request25);
-        assertEquals(BigInteger.ZERO, request25.fee);
+        assertEquals(Coin.ZERO, request25.fee);
         assertEquals(1, request25.tx.getInputs().size());
         assertEquals(72, request25.tx.getOutputs().size());
         // Now reset request19 and give it a fee per kb
         request25.tx.clearInputs();
         request25 = SendRequest.forTx(request25.tx);
-        request25.feePerKb = CENT.divide(BigInteger.valueOf(3));
+        request25.feePerKb = CENT.divide(Coin.valueOf(3));
         request25.ensureMinRequiredFee = false;
         request25.shuffleOutputs = false;
         wallet.completeTx(request25);
-        assertEquals(CENT.subtract(BigInteger.ONE), request25.fee);
+        assertEquals(CENT.subtract(Coin.ONE), request25.fee);
         assertEquals(2, request25.tx.getInputs().size());
-        BigInteger outValue25 = BigInteger.ZERO;
+        Coin outValue25 = Coin.ZERO;
         for (TransactionOutput out : request25.tx.getOutputs())
             outValue25 = outValue25.add(out.getValue());
         // Our change output should be one satoshi
-        assertEquals(BigInteger.ONE, request25.tx.getOutput(request25.tx.getOutputs().size() - 1).getValue());
+        assertEquals(Coin.ONE, request25.tx.getOutput(request25.tx.getOutputs().size() - 1).getValue());
         // and our fee should be CENT-1 satoshi
-        assertEquals(outValue25, Utils.COIN.add(BigInteger.ONE));
+        assertEquals(outValue25, Utils.COIN.add(Coin.ONE));
 
         // Spend our CENT output.
         Transaction spendTx5 = new Transaction(params);
@@ -1849,14 +1849,14 @@ public class WalletTest extends TestWithWallet {
         request26.tx.addOutput(CENT.subtract(
                 Transaction.REFERENCE_DEFAULT_MIN_TX_FEE.add(Transaction.MIN_NONDUST_OUTPUT)), notMyAddr);
         assertTrue(request26.tx.bitcoinSerialize().length > 1000);
-        request26.feePerKb = BigInteger.ONE;
+        request26.feePerKb = Coin.ONE;
         wallet.completeTx(request26);
         assertEquals(Transaction.REFERENCE_DEFAULT_MIN_TX_FEE.add(Transaction.MIN_NONDUST_OUTPUT), request26.fee);
         Transaction spend26 = request26.tx;
         // If a transaction is over 1kb, the set fee should be added
         assertEquals(100, spend26.getOutputs().size());
         // We optimize for priority, so the output selected should be the largest one
-        BigInteger outValue26 = BigInteger.ZERO;
+        Coin outValue26 = Coin.ZERO;
         for (TransactionOutput out : spend26.getOutputs())
             outValue26 = outValue26.add(out.getValue());
         assertEquals(outValue26, Utils.COIN.subtract(
@@ -1866,7 +1866,7 @@ public class WalletTest extends TestWithWallet {
     @Test
     public void basicCategoryStepTest() throws Exception {
         // Creates spends that step through the possible fee solver categories
-        SendRequest.DEFAULT_FEE_PER_KB = BigInteger.ZERO;
+        SendRequest.DEFAULT_FEE_PER_KB = Coin.ZERO;
         // Make sure TestWithWallet isnt doing anything crazy.
         assertEquals(0, wallet.getTransactions(true).size());
 
@@ -1882,9 +1882,9 @@ public class WalletTest extends TestWithWallet {
         }
 
         // Create a spend that will throw away change (category 3 type 2 in which the change causes fee which is worth more than change)
-        SendRequest request1 = SendRequest.to(notMyAddr, CENT.add(Transaction.REFERENCE_DEFAULT_MIN_TX_FEE).subtract(BigInteger.ONE));
+        SendRequest request1 = SendRequest.to(notMyAddr, CENT.add(Transaction.REFERENCE_DEFAULT_MIN_TX_FEE).subtract(Coin.ONE));
         wallet.completeTx(request1);
-        assertEquals(BigInteger.ONE, request1.fee);
+        assertEquals(Coin.ONE, request1.fee);
         assertEquals(request1.tx.getInputs().size(), i); // We should have spent all inputs
 
         // Give us one more input...
@@ -1893,9 +1893,9 @@ public class WalletTest extends TestWithWallet {
         wallet.receiveFromBlock(tx1, block, AbstractBlockChain.NewBlockType.BEST_CHAIN, i);
 
         // ... and create a spend that will throw away change (category 3 type 1 in which the change causes dust output)
-        SendRequest request2 = SendRequest.to(notMyAddr, CENT.add(Transaction.REFERENCE_DEFAULT_MIN_TX_FEE).subtract(BigInteger.ONE));
+        SendRequest request2 = SendRequest.to(notMyAddr, CENT.add(Transaction.REFERENCE_DEFAULT_MIN_TX_FEE).subtract(Coin.ONE));
         wallet.completeTx(request2);
-        assertEquals(BigInteger.ONE, request2.fee);
+        assertEquals(Coin.ONE, request2.fee);
         assertEquals(request2.tx.getInputs().size(), i - 1); // We should have spent all inputs - 1
 
         // Give us one more input...
@@ -1905,16 +1905,16 @@ public class WalletTest extends TestWithWallet {
 
         // ... and create a spend that will throw away change (category 3 type 1 in which the change causes dust output)
         // but that also could have been category 2 if it wanted
-        SendRequest request3 = SendRequest.to(notMyAddr, CENT.add(Transaction.REFERENCE_DEFAULT_MIN_TX_FEE).subtract(BigInteger.ONE));
+        SendRequest request3 = SendRequest.to(notMyAddr, CENT.add(Transaction.REFERENCE_DEFAULT_MIN_TX_FEE).subtract(Coin.ONE));
         wallet.completeTx(request3);
-        assertEquals(BigInteger.ONE, request3.fee);
+        assertEquals(Coin.ONE, request3.fee);
         assertEquals(request3.tx.getInputs().size(), i - 2); // We should have spent all inputs - 2
 
         //
-        SendRequest request4 = SendRequest.to(notMyAddr, CENT.add(Transaction.REFERENCE_DEFAULT_MIN_TX_FEE).subtract(BigInteger.ONE));
-        request4.feePerKb = Transaction.REFERENCE_DEFAULT_MIN_TX_FEE.divide(BigInteger.valueOf(request3.tx.bitcoinSerialize().length));
+        SendRequest request4 = SendRequest.to(notMyAddr, CENT.add(Transaction.REFERENCE_DEFAULT_MIN_TX_FEE).subtract(Coin.ONE));
+        request4.feePerKb = Transaction.REFERENCE_DEFAULT_MIN_TX_FEE.divide(Coin.valueOf(request3.tx.bitcoinSerialize().length));
         wallet.completeTx(request4);
-        assertEquals(BigInteger.ONE, request4.fee);
+        assertEquals(Coin.ONE, request4.fee);
         assertEquals(request4.tx.getInputs().size(), i - 2); // We should have spent all inputs - 2
 
         // Give us a few more inputs...
@@ -1925,9 +1925,9 @@ public class WalletTest extends TestWithWallet {
         }
 
         // ...that is just slightly less than is needed for category 1
-        SendRequest request5 = SendRequest.to(notMyAddr, CENT.add(Transaction.REFERENCE_DEFAULT_MIN_TX_FEE).subtract(BigInteger.ONE));
+        SendRequest request5 = SendRequest.to(notMyAddr, CENT.add(Transaction.REFERENCE_DEFAULT_MIN_TX_FEE).subtract(Coin.ONE));
         wallet.completeTx(request5);
-        assertEquals(BigInteger.ONE, request5.fee);
+        assertEquals(Coin.ONE, request5.fee);
         assertEquals(1, request5.tx.getOutputs().size()); // We should have no change output
 
         // Give us one more input...
@@ -1936,9 +1936,9 @@ public class WalletTest extends TestWithWallet {
         wallet.receiveFromBlock(tx4, block, AbstractBlockChain.NewBlockType.BEST_CHAIN, i);
 
         // ... that puts us in category 1 (no fee!)
-        SendRequest request6 = SendRequest.to(notMyAddr, CENT.add(Transaction.REFERENCE_DEFAULT_MIN_TX_FEE).subtract(BigInteger.ONE));
+        SendRequest request6 = SendRequest.to(notMyAddr, CENT.add(Transaction.REFERENCE_DEFAULT_MIN_TX_FEE).subtract(Coin.ONE));
         wallet.completeTx(request6);
-        assertEquals(BigInteger.ZERO, request6.fee);
+        assertEquals(Coin.ZERO, request6.fee);
         assertEquals(2, request6.tx.getOutputs().size()); // We should have a change output
 
         SendRequest.DEFAULT_FEE_PER_KB = Transaction.REFERENCE_DEFAULT_MIN_TX_FEE;
@@ -1956,14 +1956,14 @@ public class WalletTest extends TestWithWallet {
         // Generate a ton of small outputs
         StoredBlock block = new StoredBlock(makeSolvedTestBlock(blockStore, notMyAddr), BigInteger.ONE, 1);
         int i = 0;
-        while (i <= CENT.divide(Transaction.REFERENCE_DEFAULT_MIN_TX_FEE.multiply(BigInteger.TEN)).longValue()) {
-            Transaction tx = createFakeTxWithChangeAddress(params, Transaction.REFERENCE_DEFAULT_MIN_TX_FEE.multiply(BigInteger.TEN), myAddress, notMyAddr);
+        while (i <= CENT.divide(Transaction.REFERENCE_DEFAULT_MIN_TX_FEE.multiply(Coin.TEN)).longValue()) {
+            Transaction tx = createFakeTxWithChangeAddress(params, Transaction.REFERENCE_DEFAULT_MIN_TX_FEE.multiply(Coin.TEN), myAddress, notMyAddr);
             tx.getInput(0).setSequenceNumber(i++); // Keep every transaction unique
             wallet.receiveFromBlock(tx, block, AbstractBlockChain.NewBlockType.BEST_CHAIN, i);
         }
 
         // The selector will choose 2 with MIN_TX_FEE fee
-        SendRequest request1 = SendRequest.to(notMyAddr, CENT.add(BigInteger.ONE));
+        SendRequest request1 = SendRequest.to(notMyAddr, CENT.add(Coin.ONE));
         wallet.completeTx(request1);
         assertEquals(Transaction.REFERENCE_DEFAULT_MIN_TX_FEE, request1.fee);
         assertEquals(request1.tx.getInputs().size(), i); // We should have spent all inputs
@@ -2002,16 +2002,16 @@ public class WalletTest extends TestWithWallet {
         wallet.receiveFromBlock(tx, block, AbstractBlockChain.NewBlockType.BEST_CHAIN, 0);
         Transaction tx2 = createFakeTx(params, CENT, myAddress);
         wallet.receiveFromBlock(tx2, block, AbstractBlockChain.NewBlockType.BEST_CHAIN, 1);
-        Transaction tx3 = createFakeTx(params, BigInteger.ONE, myAddress);
+        Transaction tx3 = createFakeTx(params, Coin.ONE, myAddress);
         wallet.receiveFromBlock(tx3, block, AbstractBlockChain.NewBlockType.BEST_CHAIN, 2);
 
         // Create a transaction who's max size could be up to 1000 (if signatures were maximum size)
-        SendRequest request1 = SendRequest.to(notMyAddr, Utils.COIN.subtract(CENT.multiply(BigInteger.valueOf(17))));
+        SendRequest request1 = SendRequest.to(notMyAddr, Utils.COIN.subtract(CENT.multiply(Coin.valueOf(17))));
         for (int i = 0; i < 16; i++)
             request1.tx.addOutput(CENT, notMyAddr);
         request1.tx.addOutput(new TransactionOutput(params, request1.tx, CENT, new byte[16]));
-        request1.fee = BigInteger.ONE;
-        request1.feePerKb = BigInteger.ONE;
+        request1.fee = Coin.ONE;
+        request1.feePerKb = Coin.ONE;
         // We get a category 2 using COIN+CENT
         // It spends COIN + 1(fee) and because its output is thus < CENT, we have to pay MIN_TX_FEE
         // When it tries category 1, its too large and requires COIN + 2 (fee)
@@ -2021,18 +2021,18 @@ public class WalletTest extends TestWithWallet {
         assertEquals(2, request1.tx.getInputs().size());
 
         // We then add one more satoshi output to the wallet
-        Transaction tx4 = createFakeTx(params, BigInteger.ONE, myAddress);
+        Transaction tx4 = createFakeTx(params, Coin.ONE, myAddress);
         wallet.receiveFromBlock(tx4, block, AbstractBlockChain.NewBlockType.BEST_CHAIN, 3);
 
         // Create a transaction who's max size could be up to 1000 (if signatures were maximum size)
-        SendRequest request2 = SendRequest.to(notMyAddr, Utils.COIN.subtract(CENT.multiply(BigInteger.valueOf(17))));
+        SendRequest request2 = SendRequest.to(notMyAddr, Utils.COIN.subtract(CENT.multiply(Coin.valueOf(17))));
         for (int i = 0; i < 16; i++)
             request2.tx.addOutput(CENT, notMyAddr);
         request2.tx.addOutput(new TransactionOutput(params, request2.tx, CENT, new byte[16]));
-        request2.feePerKb = BigInteger.ONE;
+        request2.feePerKb = Coin.ONE;
         // The process is the same as above, but now we can complete category 1 with one more input, and pay a fee of 2
         wallet.completeTx(request2);
-        assertEquals(BigInteger.valueOf(2), request2.fee);
+        assertEquals(Coin.valueOf(2), request2.fee);
         assertEquals(4, request2.tx.getInputs().size());
     }
 
@@ -2107,7 +2107,7 @@ public class WalletTest extends TestWithWallet {
         // Check that if a wallet listener throws an exception, the others still run.
         wallet.addEventListener(new AbstractWalletEventListener() {
             @Override
-            public void onCoinsReceived(Wallet wallet, Transaction tx, BigInteger prevBalance, BigInteger newBalance) {
+            public void onCoinsReceived(Wallet wallet, Transaction tx, Coin prevBalance, Coin newBalance) {
                 log.info("onCoinsReceived 1");
                 throw new RuntimeException("barf");
             }
@@ -2115,7 +2115,7 @@ public class WalletTest extends TestWithWallet {
         final AtomicInteger flag = new AtomicInteger();
         wallet.addEventListener(new AbstractWalletEventListener() {
             @Override
-            public void onCoinsReceived(Wallet wallet, Transaction tx, BigInteger prevBalance, BigInteger newBalance) {
+            public void onCoinsReceived(Wallet wallet, Transaction tx, Coin prevBalance, Coin newBalance) {
                 log.info("onCoinsReceived 2");
                 flag.incrementAndGet();
             }
@@ -2134,13 +2134,13 @@ public class WalletTest extends TestWithWallet {
         StoredBlock block = new StoredBlock(makeSolvedTestBlock(blockStore, new ECKey().toAddress(params)), BigInteger.ONE, 1);
         Random rng = new Random();
         for (int i = 0; i < rng.nextInt(100) + 1; i++) {
-            Transaction tx = createFakeTx(params, BigInteger.valueOf(rng.nextInt((int) Utils.COIN.longValue())), myAddress);
+            Transaction tx = createFakeTx(params, Coin.valueOf(rng.nextInt((int) Utils.COIN.longValue())), myAddress);
             wallet.receiveFromBlock(tx, block, AbstractBlockChain.NewBlockType.BEST_CHAIN, i);
         }
         SendRequest request = SendRequest.emptyWallet(new ECKey().toAddress(params));
         wallet.completeTx(request);
         wallet.commitTx(request.tx);
-        assertEquals(BigInteger.ZERO, wallet.getBalance());
+        assertEquals(Coin.ZERO, wallet.getBalance());
     }
 
     @Test
@@ -2153,7 +2153,7 @@ public class WalletTest extends TestWithWallet {
         SendRequest request = SendRequest.emptyWallet(outputKey);
         wallet.completeTx(request);
         wallet.commitTx(request.tx);
-        assertEquals(BigInteger.ZERO, wallet.getBalance());
+        assertEquals(Coin.ZERO, wallet.getBalance());
         assertEquals(CENT, request.tx.getOutput(0).getValue());
 
         // Add 1 confirmed cent and 1 unconfirmed cent. Verify only one cent is emptied because of the coin selection
@@ -2166,22 +2166,22 @@ public class WalletTest extends TestWithWallet {
         request = SendRequest.emptyWallet(outputKey);
         wallet.completeTx(request);
         wallet.commitTx(request.tx);
-        assertEquals(BigInteger.ZERO, wallet.getBalance());
+        assertEquals(Coin.ZERO, wallet.getBalance());
         assertEquals(CENT, request.tx.getOutput(0).getValue());
 
         // Add just under 0.01
         StoredBlock block2 = new StoredBlock(block.getHeader().createNextBlock(outputKey), BigInteger.ONE, 2);
-        tx = createFakeTx(params, CENT.subtract(BigInteger.ONE), myAddress);
+        tx = createFakeTx(params, CENT.subtract(Coin.ONE), myAddress);
         wallet.receiveFromBlock(tx, block2, AbstractBlockChain.NewBlockType.BEST_CHAIN, 0);
         request = SendRequest.emptyWallet(outputKey);
         wallet.completeTx(request);
         wallet.commitTx(request.tx);
-        assertEquals(BigInteger.ZERO, wallet.getBalance());
-        assertEquals(CENT.subtract(BigInteger.ONE).subtract(Transaction.REFERENCE_DEFAULT_MIN_TX_FEE), request.tx.getOutput(0).getValue());
+        assertEquals(Coin.ZERO, wallet.getBalance());
+        assertEquals(CENT.subtract(Coin.ONE).subtract(Transaction.REFERENCE_DEFAULT_MIN_TX_FEE), request.tx.getOutput(0).getValue());
 
         // Add an unsendable value
         StoredBlock block3 = new StoredBlock(block2.getHeader().createNextBlock(outputKey), BigInteger.ONE, 3);
-        BigInteger outputValue = Transaction.MIN_NONDUST_OUTPUT.add(Transaction.REFERENCE_DEFAULT_MIN_TX_FEE).subtract(BigInteger.ONE);
+        Coin outputValue = Transaction.MIN_NONDUST_OUTPUT.add(Transaction.REFERENCE_DEFAULT_MIN_TX_FEE).subtract(Coin.ONE);
         tx = createFakeTx(params, outputValue, myAddress);
         wallet.receiveFromBlock(tx, block3, AbstractBlockChain.NewBlockType.BEST_CHAIN, 0);
         request = SendRequest.emptyWallet(outputKey);
@@ -2192,7 +2192,7 @@ public class WalletTest extends TestWithWallet {
         request.ensureMinRequiredFee = false;
         wallet.completeTx(request);
         wallet.commitTx(request.tx);
-        assertEquals(BigInteger.ZERO, wallet.getBalance());
+        assertEquals(Coin.ZERO, wallet.getBalance());
         assertEquals(outputValue, request.tx.getOutput(0).getValue());
     }
 
@@ -2220,7 +2220,7 @@ public class WalletTest extends TestWithWallet {
         wallet.setKeyRotationTime(compromiseTime);
         assertTrue(wallet.isKeyRotating(key1));
         Transaction tx = broadcaster.waitForTransaction();
-        final BigInteger THREE_CENTS = CENT.add(CENT).add(CENT);
+        final Coin THREE_CENTS = CENT.add(CENT).add(CENT);
         assertEquals(THREE_CENTS, tx.getValueSentFromMe(wallet));
         assertEquals(THREE_CENTS.subtract(Transaction.REFERENCE_DEFAULT_MIN_TX_FEE), tx.getValueSentToMe(wallet));
         // TX is a raw pay to pubkey.
@@ -2281,11 +2281,11 @@ public class WalletTest extends TestWithWallet {
         wallet.setKeyRotationTime(compromise);
 
         Transaction tx = broadcaster.waitForTransaction();
-        final BigInteger valueSentToMe = tx.getValueSentToMe(wallet);
-        BigInteger fee = tx.getValueSentFromMe(wallet).subtract(valueSentToMe);
-        assertEquals(BigInteger.valueOf(900000), fee);
+        final Coin valueSentToMe = tx.getValueSentToMe(wallet);
+        Coin fee = tx.getValueSentFromMe(wallet).subtract(valueSentToMe);
+        assertEquals(Coin.valueOf(900000), fee);
         assertEquals(KeyTimeCoinSelector.MAX_SIMULTANEOUS_INPUTS, tx.getInputs().size());
-        assertEquals(BigInteger.valueOf(599100000), valueSentToMe);
+        assertEquals(Coin.valueOf(599100000), valueSentToMe);
 
         tx = broadcaster.waitForTransaction();
         assertNotNull(tx);
@@ -2347,11 +2347,11 @@ public class WalletTest extends TestWithWallet {
             }
         });
         assertTrue(wallet.isPendingTransactionRelevant(tx));
-        assertEquals(BigInteger.ZERO, wallet.getBalance());
-        assertEquals(BigInteger.ZERO, wallet.getBalance(Wallet.BalanceType.ESTIMATED));
+        assertEquals(Coin.ZERO, wallet.getBalance());
+        assertEquals(Coin.ZERO, wallet.getBalance(Wallet.BalanceType.ESTIMATED));
         wallet.receivePending(tx, null);
-        assertEquals(BigInteger.ZERO, wallet.getBalance());
-        assertEquals(BigInteger.ZERO, wallet.getBalance(Wallet.BalanceType.ESTIMATED));
+        assertEquals(Coin.ZERO, wallet.getBalance());
+        assertEquals(Coin.ZERO, wallet.getBalance(Wallet.BalanceType.ESTIMATED));
         assertTrue(bool.get());
         // Confirm it in the same manner as how Bloom filtered blocks do. Verify it shows up.
         StoredBlock block = createFakeBlock(blockStore, tx).storedBlock;
diff --git a/core/src/test/java/com/google/bitcoin/protocols/channels/ChannelConnectionTest.java b/core/src/test/java/com/google/bitcoin/protocols/channels/ChannelConnectionTest.java
index 29f0a51a..84b38891 100644
--- a/core/src/test/java/com/google/bitcoin/protocols/channels/ChannelConnectionTest.java
+++ b/core/src/test/java/com/google/bitcoin/protocols/channels/ChannelConnectionTest.java
@@ -33,7 +33,6 @@ import javax.annotation.Nullable;
 import java.io.ByteArrayInputStream;
 import java.io.ByteArrayOutputStream;
 import java.io.File;
-import java.math.BigInteger;
 import java.net.InetSocketAddress;
 import java.net.SocketAddress;
 import java.util.Arrays;
@@ -116,7 +115,7 @@ public class ChannelConnectionTest extends TestWithWallet {
         // Test with network code and without any issues. We'll broadcast two txns: multisig contract and settle transaction.
         final SettableFuture<ListenableFuture<PaymentChannelServerState>> serverCloseFuture = SettableFuture.create();
         final SettableFuture<Sha256Hash> channelOpenFuture = SettableFuture.create();
-        final BlockingQueue<BigInteger> q = new LinkedBlockingQueue<BigInteger>();
+        final BlockingQueue<Coin> q = new LinkedBlockingQueue<Coin>();
         final PaymentChannelServerListener server = new PaymentChannelServerListener(mockBroadcaster, serverWallet, 30, Utils.COIN,
                 new PaymentChannelServerListener.HandlerFactory() {
                     @Nullable
@@ -129,7 +128,7 @@ public class ChannelConnectionTest extends TestWithWallet {
                             }
 
                             @Override
-                            public void paymentIncrease(BigInteger by, BigInteger to) {
+                            public void paymentIncrease(Coin by, Coin to) {
                                 q.add(to);
                             }
 
@@ -169,7 +168,7 @@ public class ChannelConnectionTest extends TestWithWallet {
         });
 
         Thread.sleep(1250); // No timeouts once the channel is open
-        BigInteger amount = client.state().getValueSpent();
+        Coin amount = client.state().getValueSpent();
         assertEquals(amount, q.take());
         client.incrementPayment(Utils.CENT).get();
         amount = amount.add(Utils.CENT);
@@ -193,7 +192,7 @@ public class ChannelConnectionTest extends TestWithWallet {
         broadcastTxPause.release();
         Transaction settleTx = broadcasts.take();
         assertEquals(PaymentChannelServerState.State.CLOSED, serverState.getState());
-        if (!serverState.getBestValueToMe().equals(amount) || !serverState.getFeePaid().equals(BigInteger.ZERO))
+        if (!serverState.getBestValueToMe().equals(amount) || !serverState.getFeePaid().equals(Coin.ZERO))
             fail();
         assertTrue(channels.mapChannels.isEmpty());
 
@@ -282,7 +281,7 @@ public class ChannelConnectionTest extends TestWithWallet {
         server.receiveMessage(pair.clientRecorder.checkNextMsg(MessageType.CLIENT_VERSION));
         client.receiveMessage(pair.serverRecorder.checkNextMsg(MessageType.SERVER_VERSION));
         final Protos.TwoWayChannelMessage initiateMsg = pair.serverRecorder.checkNextMsg(MessageType.INITIATE);
-        BigInteger minPayment = BigInteger.valueOf(initiateMsg.getInitiate().getMinPayment());
+        Coin minPayment = Coin.valueOf(initiateMsg.getInitiate().getMinPayment());
         client.receiveMessage(initiateMsg);
         server.receiveMessage(pair.clientRecorder.checkNextMsg(MessageType.PROVIDE_REFUND));
         client.receiveMessage(pair.serverRecorder.checkNextMsg(MessageType.RETURN_REFUND));
@@ -297,7 +296,7 @@ public class ChannelConnectionTest extends TestWithWallet {
         assertNull(pair.clientRecorder.q.poll());
         assertEquals(minPayment, client.state().getValueSpent());
         // Send a bitcent.
-        BigInteger amount = minPayment.add(Utils.CENT);
+        Coin amount = minPayment.add(Utils.CENT);
         client.incrementPayment(Utils.CENT);
         server.receiveMessage(pair.clientRecorder.checkNextMsg(MessageType.UPDATE_PAYMENT));
         assertEquals(amount, pair.serverRecorder.q.take());
@@ -463,7 +462,7 @@ public class ChannelConnectionTest extends TestWithWallet {
         assertEquals(CloseReason.NO_ACCEPTABLE_VERSION, pair.clientRecorder.q.take());
         // Double-check that we cant do anything that requires an open channel
         try {
-            client.incrementPayment(BigInteger.ONE);
+            client.incrementPayment(Coin.ONE);
             fail();
         } catch (IllegalStateException e) { }
     }
@@ -489,7 +488,7 @@ public class ChannelConnectionTest extends TestWithWallet {
         assertEquals(CloseReason.TIME_WINDOW_TOO_LARGE, pair.clientRecorder.q.take());
         // Double-check that we cant do anything that requires an open channel
         try {
-            client.incrementPayment(BigInteger.ONE);
+            client.incrementPayment(Coin.ONE);
             fail();
         } catch (IllegalStateException e) { }
     }
@@ -505,7 +504,7 @@ public class ChannelConnectionTest extends TestWithWallet {
         client.receiveMessage(pair.serverRecorder.checkNextMsg(MessageType.SERVER_VERSION));
         client.receiveMessage(Protos.TwoWayChannelMessage.newBuilder()
                 .setInitiate(Protos.Initiate.newBuilder().setExpireTimeSecs(Utils.currentTimeSeconds())
-                        .setMinAcceptedChannelSize(Utils.COIN.add(BigInteger.ONE).longValue())
+                        .setMinAcceptedChannelSize(Utils.COIN.add(Coin.ONE).longValue())
                         .setMultisigKey(ByteString.copyFrom(new ECKey().getPubKey()))
                         .setMinPayment(Transaction.MIN_NONDUST_OUTPUT.longValue()))
                 .setType(MessageType.INITIATE).build());
@@ -513,17 +512,17 @@ public class ChannelConnectionTest extends TestWithWallet {
         assertEquals(CloseReason.SERVER_REQUESTED_TOO_MUCH_VALUE, pair.clientRecorder.q.take());
         // Double-check that we cant do anything that requires an open channel
         try {
-            client.incrementPayment(BigInteger.ONE);
+            client.incrementPayment(Coin.ONE);
             fail();
         } catch (IllegalStateException e) { }
 
         // Now check that if the server has a lower min size than what we are willing to spend, we do actually open
         // a channel of that size.
-        sendMoneyToWallet(Utils.COIN.multiply(BigInteger.TEN), AbstractBlockChain.NewBlockType.BEST_CHAIN);
+        sendMoneyToWallet(Utils.COIN.multiply(Coin.TEN), AbstractBlockChain.NewBlockType.BEST_CHAIN);
 
         pair = ChannelTestUtils.makeRecorders(serverWallet, mockBroadcaster);
         server = pair.server;
-        final BigInteger myValue = Utils.COIN.multiply(BigInteger.TEN);
+        final Coin myValue = Utils.COIN.multiply(Coin.TEN);
         client = new PaymentChannelClient(wallet, myKey, myValue, Sha256Hash.ZERO_HASH, pair.clientRecorder);
         client.connectionOpen();
         server.connectionOpen();
@@ -531,7 +530,7 @@ public class ChannelConnectionTest extends TestWithWallet {
         client.receiveMessage(pair.serverRecorder.checkNextMsg(MessageType.SERVER_VERSION));
         client.receiveMessage(Protos.TwoWayChannelMessage.newBuilder()
                 .setInitiate(Protos.Initiate.newBuilder().setExpireTimeSecs(Utils.currentTimeSeconds())
-                        .setMinAcceptedChannelSize(Utils.COIN.add(BigInteger.ONE).longValue())
+                        .setMinAcceptedChannelSize(Utils.COIN.add(Coin.ONE).longValue())
                         .setMultisigKey(ByteString.copyFrom(new ECKey().getPubKey()))
                         .setMinPayment(Transaction.REFERENCE_DEFAULT_MIN_TX_FEE.longValue()))
                 .setType(MessageType.INITIATE).build());
@@ -644,8 +643,8 @@ public class ChannelConnectionTest extends TestWithWallet {
         server.receiveMessage(pair.clientRecorder.checkNextMsg(MessageType.UPDATE_PAYMENT));
         broadcasts.take();
         // The channel is now empty.
-        assertEquals(BigInteger.ZERO, client.state().getValueRefunded());
-        pair.serverRecorder.q.take();  // Take the BigInteger.
+        assertEquals(Coin.ZERO, client.state().getValueRefunded());
+        pair.serverRecorder.q.take();  // Take the Coin.
         client.receiveMessage(pair.serverRecorder.checkNextMsg(MessageType.PAYMENT_ACK));
         client.receiveMessage(pair.serverRecorder.checkNextMsg(MessageType.CLOSE));
         assertEquals(CloseReason.SERVER_REQUESTED_CLOSE, pair.clientRecorder.q.take());
@@ -684,7 +683,7 @@ public class ChannelConnectionTest extends TestWithWallet {
             pair.clientRecorder.checkInitiated();
             assertNull(pair.serverRecorder.q.poll());
             assertNull(pair.clientRecorder.q.poll());
-            ListenableFuture<BigInteger> future = client.incrementPayment(Utils.CENT);
+            ListenableFuture<Coin> future = client.incrementPayment(Utils.CENT);
             server.receiveMessage(pair.clientRecorder.checkNextMsg(MessageType.UPDATE_PAYMENT));
             pair.serverRecorder.q.take();
             client.receiveMessage(pair.serverRecorder.checkNextMsg(MessageType.PAYMENT_ACK));
diff --git a/core/src/test/java/com/google/bitcoin/protocols/channels/ChannelTestUtils.java b/core/src/test/java/com/google/bitcoin/protocols/channels/ChannelTestUtils.java
index 3eff2278..1370b798 100644
--- a/core/src/test/java/com/google/bitcoin/protocols/channels/ChannelTestUtils.java
+++ b/core/src/test/java/com/google/bitcoin/protocols/channels/ChannelTestUtils.java
@@ -1,12 +1,13 @@
 package com.google.bitcoin.protocols.channels;
 
+import com.google.bitcoin.core.Coin;
 import com.google.bitcoin.core.Sha256Hash;
 import com.google.bitcoin.core.TransactionBroadcaster;
 import com.google.bitcoin.core.Utils;
 import com.google.bitcoin.core.Wallet;
+
 import org.bitcoin.paymentchannel.Protos;
 
-import java.math.BigInteger;
 import java.util.concurrent.BlockingQueue;
 import java.util.concurrent.LinkedBlockingQueue;
 
@@ -35,7 +36,7 @@ public class ChannelTestUtils {
         }
 
         @Override
-        public void paymentIncrease(BigInteger by, BigInteger to) {
+        public void paymentIncrease(Coin by, Coin to) {
             q.add(to);
         }
 
@@ -49,8 +50,8 @@ public class ChannelTestUtils {
             return msg;
         }
 
-        public void checkTotalPayment(BigInteger valueSoFar) throws InterruptedException {
-            BigInteger lastSeen = (BigInteger) q.take();
+        public void checkTotalPayment(Coin valueSoFar) throws InterruptedException {
+            Coin lastSeen = (Coin) q.take();
             assertEquals(lastSeen, valueSoFar);
         }
     }
diff --git a/core/src/test/java/com/google/bitcoin/protocols/channels/PaymentChannelStateTest.java b/core/src/test/java/com/google/bitcoin/protocols/channels/PaymentChannelStateTest.java
index d9d577d1..23bfe79a 100644
--- a/core/src/test/java/com/google/bitcoin/protocols/channels/PaymentChannelStateTest.java
+++ b/core/src/test/java/com/google/bitcoin/protocols/channels/PaymentChannelStateTest.java
@@ -40,7 +40,7 @@ import static org.junit.Assert.*;
 
 public class PaymentChannelStateTest extends TestWithWallet {
     private ECKey serverKey;
-    private BigInteger halfCoin;
+    private Coin halfCoin;
     private Wallet serverWallet;
     private PaymentChannelServerState serverState;
     private PaymentChannelClientState clientState;
@@ -94,7 +94,7 @@ public class PaymentChannelStateTest extends TestWithWallet {
     @Test
     public void stateErrors() throws Exception {
         PaymentChannelClientState channelState = new PaymentChannelClientState(wallet, myKey, serverKey,
-                Utils.COIN.multiply(BigInteger.TEN), 20);
+                Utils.COIN.multiply(Coin.TEN), 20);
         assertEquals(PaymentChannelClientState.State.NEW, channelState.getState());
         try {
             channelState.getMultisigContract();
@@ -164,8 +164,8 @@ public class PaymentChannelStateTest extends TestWithWallet {
         assertFalse(clientWalletMultisigContract.getInput(0).getConnectedOutput().getSpentBy().getParentTransaction().getHash().equals(refund.getHash()));
 
         // Both client and server are now in the ready state. Simulate a few micropayments of 0.005 bitcoins.
-        BigInteger size = halfCoin.divide(BigInteger.TEN).divide(BigInteger.TEN);
-        BigInteger totalPayment = BigInteger.ZERO;
+        Coin size = halfCoin.divide(Coin.TEN).divide(Coin.TEN);
+        Coin totalPayment = Coin.ZERO;
         for (int i = 0; i < 4; i++) {
             byte[] signature = clientState.incrementPaymentBy(size).signature.encodeToBitcoin();
             totalPayment = totalPayment.add(size);
@@ -194,10 +194,10 @@ public class PaymentChannelStateTest extends TestWithWallet {
         // Create a block with the payment transaction in it and give it to both wallets
         chain.add(makeSolvedTestBlock(blockStore.getChainHead().getHeader(), reserializedCloseTx));
 
-        assertEquals(size.multiply(BigInteger.valueOf(5)), serverWallet.getBalance());
+        assertEquals(size.multiply(Coin.valueOf(5)), serverWallet.getBalance());
         assertEquals(0, serverWallet.getPendingTransactions().size());
 
-        assertEquals(Utils.COIN.subtract(size.multiply(BigInteger.valueOf(5))), wallet.getBalance());
+        assertEquals(Utils.COIN.subtract(size.multiply(Coin.valueOf(5))), wallet.getBalance());
         assertEquals(0, wallet.getPendingTransactions().size());
         assertEquals(3, wallet.getTransactions(false).size());
 
@@ -218,7 +218,7 @@ public class PaymentChannelStateTest extends TestWithWallet {
 
         // Spend the client wallet's one coin
         Transaction spendCoinTx = wallet.sendCoinsOffline(Wallet.SendRequest.to(new ECKey().toAddress(params), Utils.COIN));
-        assertEquals(BigInteger.ZERO, wallet.getBalance());
+        assertEquals(Coin.ZERO, wallet.getBalance());
         chain.add(makeSolvedTestBlock(blockStore.getChainHead().getHeader(), spendCoinTx, createFakeTx(params, Utils.CENT, myAddress)));
         assertEquals(Utils.CENT, wallet.getBalance());
 
@@ -233,12 +233,12 @@ public class PaymentChannelStateTest extends TestWithWallet {
         assertEquals(PaymentChannelServerState.State.WAITING_FOR_REFUND_TRANSACTION, serverState.getState());
 
         clientState = new PaymentChannelClientState(wallet, myKey, ECKey.fromPublicOnly(serverKey.getPubKey()),
-                                                    Utils.CENT.divide(BigInteger.valueOf(2)), EXPIRE_TIME);
+                                                    Utils.CENT.divide(Coin.valueOf(2)), EXPIRE_TIME);
         assertEquals(PaymentChannelClientState.State.NEW, clientState.getState());
-        assertEquals(Utils.CENT.divide(BigInteger.valueOf(2)), clientState.getTotalValue());
+        assertEquals(Utils.CENT.divide(Coin.valueOf(2)), clientState.getTotalValue());
         clientState.initiate();
         // We will have to pay min_tx_fee twice - both the multisig contract and the refund tx
-        assertEquals(clientState.getRefundTxFees(), Transaction.REFERENCE_DEFAULT_MIN_TX_FEE.multiply(BigInteger.valueOf(2)));
+        assertEquals(clientState.getRefundTxFees(), Transaction.REFERENCE_DEFAULT_MIN_TX_FEE.multiply(Coin.valueOf(2)));
         assertEquals(PaymentChannelClientState.State.INITIATED, clientState.getState());
 
         // Send the refund tx from client to server and get back the signature.
@@ -269,8 +269,8 @@ public class PaymentChannelStateTest extends TestWithWallet {
         assertEquals(PaymentChannelServerState.State.READY, serverState.getState());
 
         // Pay a tiny bit
-        serverState.incrementPayment(Utils.CENT.divide(BigInteger.valueOf(2)).subtract(Utils.CENT.divide(BigInteger.TEN)),
-                clientState.incrementPaymentBy(Utils.CENT.divide(BigInteger.TEN)).signature.encodeToBitcoin());
+        serverState.incrementPayment(Utils.CENT.divide(Coin.valueOf(2)).subtract(Utils.CENT.divide(Coin.TEN)),
+                clientState.incrementPaymentBy(Utils.CENT.divide(Coin.TEN)).signature.encodeToBitcoin());
 
         // Advance time until our we get close enough to lock time that server should rebroadcast
         Utils.rollMockClock(60*60*22);
@@ -313,7 +313,7 @@ public class PaymentChannelStateTest extends TestWithWallet {
         chain.add(makeSolvedTestBlock(blockStore.getChainHead().getHeader(), multisigContract,clientBroadcastedRefund));
 
         // Make sure we actually had to pay what initialize() told us we would
-        assertEquals(wallet.getBalance(), Utils.CENT.subtract(Transaction.REFERENCE_DEFAULT_MIN_TX_FEE.multiply(BigInteger.valueOf(2))));
+        assertEquals(wallet.getBalance(), Utils.CENT.subtract(Transaction.REFERENCE_DEFAULT_MIN_TX_FEE.multiply(Coin.valueOf(2))));
 
         try {
             // After its expired, we cant still increment payment
@@ -341,7 +341,7 @@ public class PaymentChannelStateTest extends TestWithWallet {
         // Test refund transaction with any number of issues
         byte[] refundTxBytes = clientState.getIncompleteRefundTransaction().bitcoinSerialize();
         Transaction refund = new Transaction(params, refundTxBytes);
-        refund.addOutput(BigInteger.ZERO, new ECKey().toAddress(params));
+        refund.addOutput(Coin.ZERO, new ECKey().toAddress(params));
         try {
             serverState.provideRefundTransaction(refund, myKey.getPubKey());
             fail();
@@ -408,7 +408,7 @@ public class PaymentChannelStateTest extends TestWithWallet {
         clientState.fakeSave();
         assertEquals(PaymentChannelClientState.State.PROVIDE_MULTISIG_CONTRACT_TO_SERVER, clientState.getState());
 
-        try { clientState.incrementPaymentBy(BigInteger.ONE); fail(); } catch (IllegalStateException e) {}
+        try { clientState.incrementPaymentBy(Coin.ONE); fail(); } catch (IllegalStateException e) {}
 
         byte[] multisigContractSerialized = clientState.getMultisigContract().bitcoinSerialize();
 
@@ -424,7 +424,7 @@ public class PaymentChannelStateTest extends TestWithWallet {
 
         multisigContract = new Transaction(params, multisigContractSerialized);
         multisigContract.clearOutputs();
-        multisigContract.addOutput(BigInteger.ZERO, ScriptBuilder.createMultiSigOutputScript(2, Lists.newArrayList(myKey, serverKey)));
+        multisigContract.addOutput(Coin.ZERO, ScriptBuilder.createMultiSigOutputScript(2, Lists.newArrayList(myKey, serverKey)));
         try {
             serverState.provideMultiSigContract(multisigContract);
             fail();
@@ -451,8 +451,8 @@ public class PaymentChannelStateTest extends TestWithWallet {
         assertEquals(PaymentChannelServerState.State.READY, serverState.getState());
 
         // Both client and server are now in the ready state. Simulate a few micropayments of 0.005 bitcoins.
-        BigInteger size = halfCoin.divide(BigInteger.TEN).divide(BigInteger.TEN);
-        BigInteger totalPayment = BigInteger.ZERO;
+        Coin size = halfCoin.divide(Coin.TEN).divide(Coin.TEN);
+        Coin totalPayment = Coin.ZERO;
         try {
             clientState.incrementPaymentBy(Utils.COIN);
             fail();
@@ -510,12 +510,12 @@ public class PaymentChannelStateTest extends TestWithWallet {
         assertEquals(serverState.getBestValueToMe(), totalPayment);
 
         try {
-            clientState.incrementPaymentBy(BigInteger.ONE.negate());
+            clientState.incrementPaymentBy(Coin.ONE.negate());
             fail();
         } catch (ValueOutOfRangeException e) {}
 
         try {
-            clientState.incrementPaymentBy(halfCoin.subtract(size).add(BigInteger.ONE));
+            clientState.incrementPaymentBy(halfCoin.subtract(size).add(Coin.ONE));
             fail();
         } catch (ValueOutOfRangeException e) {}
     }
@@ -526,7 +526,7 @@ public class PaymentChannelStateTest extends TestWithWallet {
 
         // Spend the client wallet's one coin
         wallet.sendCoinsOffline(Wallet.SendRequest.to(new ECKey().toAddress(params), Utils.COIN));
-        assertEquals(BigInteger.ZERO, wallet.getBalance());
+        assertEquals(Coin.ZERO, wallet.getBalance());
 
         chain.add(makeSolvedTestBlock(blockStore.getChainHead().getHeader(), createFakeTx(params, Utils.CENT, myAddress)));
         assertEquals(Utils.CENT, wallet.getBalance());
@@ -538,7 +538,7 @@ public class PaymentChannelStateTest extends TestWithWallet {
         assertEquals(PaymentChannelServerState.State.WAITING_FOR_REFUND_TRANSACTION, serverState.getState());
 
         // Clearly ONE is far too small to be useful
-        clientState = new PaymentChannelClientState(wallet, myKey, ECKey.fromPublicOnly(serverKey.getPubKey()), BigInteger.ONE, EXPIRE_TIME);
+        clientState = new PaymentChannelClientState(wallet, myKey, ECKey.fromPublicOnly(serverKey.getPubKey()), Coin.ONE, EXPIRE_TIME);
         assertEquals(PaymentChannelClientState.State.NEW, clientState.getState());
         try {
             clientState.initiate();
@@ -546,7 +546,7 @@ public class PaymentChannelStateTest extends TestWithWallet {
         } catch (ValueOutOfRangeException e) {}
 
         clientState = new PaymentChannelClientState(wallet, myKey, ECKey.fromPublicOnly(serverKey.getPubKey()),
-                                                    Transaction.MIN_NONDUST_OUTPUT.subtract(BigInteger.ONE).add(Transaction.REFERENCE_DEFAULT_MIN_TX_FEE),
+                                                    Transaction.MIN_NONDUST_OUTPUT.subtract(Coin.ONE).add(Transaction.REFERENCE_DEFAULT_MIN_TX_FEE),
                 EXPIRE_TIME);
         assertEquals(PaymentChannelClientState.State.NEW, clientState.getState());
         try {
@@ -560,14 +560,14 @@ public class PaymentChannelStateTest extends TestWithWallet {
         assertEquals(PaymentChannelClientState.State.NEW, clientState.getState());
         // We'll have to pay REFERENCE_DEFAULT_MIN_TX_FEE twice (multisig+refund), and we'll end up getting back nearly nothing...
         clientState.initiate();
-        assertEquals(clientState.getRefundTxFees(), Transaction.REFERENCE_DEFAULT_MIN_TX_FEE.multiply(BigInteger.valueOf(2)));
+        assertEquals(clientState.getRefundTxFees(), Transaction.REFERENCE_DEFAULT_MIN_TX_FEE.multiply(Coin.valueOf(2)));
         assertEquals(PaymentChannelClientState.State.INITIATED, clientState.getState());
 
         // Now actually use a more useful CENT
         clientState = new PaymentChannelClientState(wallet, myKey, ECKey.fromPublicOnly(serverKey.getPubKey()), Utils.CENT, EXPIRE_TIME);
         assertEquals(PaymentChannelClientState.State.NEW, clientState.getState());
         clientState.initiate();
-        assertEquals(clientState.getRefundTxFees(), BigInteger.ZERO);
+        assertEquals(clientState.getRefundTxFees(), Coin.ZERO);
         assertEquals(PaymentChannelClientState.State.INITIATED, clientState.getState());
 
         // Send the refund tx from client to server and get back the signature.
@@ -592,16 +592,16 @@ public class PaymentChannelStateTest extends TestWithWallet {
         assertEquals(PaymentChannelServerState.State.READY, serverState.getState());
 
         // Both client and server are now in the ready state. Simulate a few micropayments
-        BigInteger totalPayment = BigInteger.ZERO;
+        Coin totalPayment = Coin.ZERO;
 
         // We can send as little as we want - its up to the server to get the fees right
-        byte[] signature = clientState.incrementPaymentBy(BigInteger.ONE).signature.encodeToBitcoin();
-        totalPayment = totalPayment.add(BigInteger.ONE);
+        byte[] signature = clientState.incrementPaymentBy(Coin.ONE).signature.encodeToBitcoin();
+        totalPayment = totalPayment.add(Coin.ONE);
         serverState.incrementPayment(Utils.CENT.subtract(totalPayment), signature);
 
         // We can't refund more than the contract is worth...
         try {
-            serverState.incrementPayment(Utils.CENT.add(BigInteger.ONE), signature);
+            serverState.incrementPayment(Utils.CENT.add(Coin.ONE), signature);
             fail();
         } catch (ValueOutOfRangeException e) {}
 
@@ -609,12 +609,12 @@ public class PaymentChannelStateTest extends TestWithWallet {
         // will correct it for us to be larger than the requested amount, to make the change output zero.
         PaymentChannelClientState.IncrementedPayment payment =
                 clientState.incrementPaymentBy(Utils.CENT.subtract(Transaction.MIN_NONDUST_OUTPUT));
-        assertEquals(Utils.CENT.subtract(BigInteger.ONE), payment.amount);
+        assertEquals(Utils.CENT.subtract(Coin.ONE), payment.amount);
         totalPayment = totalPayment.add(payment.amount);
 
         // The server also won't accept it if we do that.
         try {
-            serverState.incrementPayment(Transaction.MIN_NONDUST_OUTPUT.subtract(BigInteger.ONE), signature);
+            serverState.incrementPayment(Transaction.MIN_NONDUST_OUTPUT.subtract(Coin.ONE), signature);
             fail();
         } catch (ValueOutOfRangeException e) {}
 
@@ -678,9 +678,9 @@ public class PaymentChannelStateTest extends TestWithWallet {
         assertEquals(PaymentChannelServerState.State.READY, serverState.getState());
 
         // Both client and server are now in the ready state, split the channel in half
-        byte[] signature = clientState.incrementPaymentBy(Transaction.REFERENCE_DEFAULT_MIN_TX_FEE.subtract(BigInteger.ONE))
+        byte[] signature = clientState.incrementPaymentBy(Transaction.REFERENCE_DEFAULT_MIN_TX_FEE.subtract(Coin.ONE))
                 .signature.encodeToBitcoin();
-        BigInteger totalRefund = Utils.CENT.subtract(Transaction.REFERENCE_DEFAULT_MIN_TX_FEE.subtract(BigInteger.ONE));
+        Coin totalRefund = Utils.CENT.subtract(Transaction.REFERENCE_DEFAULT_MIN_TX_FEE.subtract(Coin.ONE));
         serverState.incrementPayment(totalRefund, signature);
 
         // We need to pay MIN_TX_FEE, but we only have MIN_NONDUST_OUTPUT
@@ -703,8 +703,8 @@ public class PaymentChannelStateTest extends TestWithWallet {
             assertTrue(e.getMessage().contains("more in fees"));
         }
 
-        signature = clientState.incrementPaymentBy(BigInteger.ONE.shiftLeft(1)).signature.encodeToBitcoin();
-        totalRefund = totalRefund.subtract(BigInteger.ONE.shiftLeft(1));
+        signature = clientState.incrementPaymentBy(Coin.ONE.shiftLeft(1)).signature.encodeToBitcoin();
+        totalRefund = totalRefund.subtract(Coin.ONE.shiftLeft(1));
         serverState.incrementPayment(totalRefund, signature);
 
         // And settle the channel.
@@ -772,8 +772,8 @@ public class PaymentChannelStateTest extends TestWithWallet {
         assertFalse(clientWalletMultisigContract.getInput(0).getConnectedOutput().getSpentBy().getParentTransaction().getHash().equals(refund.getHash()));
 
         // Both client and server are now in the ready state. Simulate a few micropayments of 0.005 bitcoins.
-        BigInteger size = halfCoin.divide(BigInteger.TEN).divide(BigInteger.TEN);
-        BigInteger totalPayment = BigInteger.ZERO;
+        Coin size = halfCoin.divide(Coin.TEN).divide(Coin.TEN);
+        Coin totalPayment = Coin.ZERO;
         for (int i = 0; i < 5; i++) {
             byte[] signature = clientState.incrementPaymentBy(size).signature.encodeToBitcoin();
             totalPayment = totalPayment.add(size);
diff --git a/core/src/test/java/com/google/bitcoin/protocols/payments/PaymentProtocolTest.java b/core/src/test/java/com/google/bitcoin/protocols/payments/PaymentProtocolTest.java
index d4f6efa1..7db55faf 100644
--- a/core/src/test/java/com/google/bitcoin/protocols/payments/PaymentProtocolTest.java
+++ b/core/src/test/java/com/google/bitcoin/protocols/payments/PaymentProtocolTest.java
@@ -20,7 +20,6 @@ import static org.junit.Assert.assertArrayEquals;
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertNotNull;
 
-import java.math.BigInteger;
 import java.security.KeyStore;
 import java.security.PrivateKey;
 import java.security.cert.X509Certificate;
@@ -35,6 +34,7 @@ import org.junit.Before;
 import org.junit.Test;
 
 import com.google.bitcoin.core.Address;
+import com.google.bitcoin.core.Coin;
 import com.google.bitcoin.core.ECKey;
 import com.google.bitcoin.core.NetworkParameters;
 import com.google.bitcoin.core.Transaction;
@@ -50,7 +50,7 @@ public class PaymentProtocolTest {
 
     // static test data
     private static final NetworkParameters NETWORK_PARAMS = UnitTestParams.get();
-    private static final BigInteger AMOUNT = BigInteger.ONE;
+    private static final Coin AMOUNT = Coin.ONE;
     private static final Address TO_ADDRESS = new ECKey().toAddress(NETWORK_PARAMS);
     private static final String MEMO = "memo";
     private static final String PAYMENT_URL = "https://example.com";
@@ -128,7 +128,7 @@ public class PaymentProtocolTest {
         // Create
         List<Transaction> transactions = new LinkedList<Transaction>();
         transactions.add(FakeTxBuilder.createFakeTx(NETWORK_PARAMS, AMOUNT, TO_ADDRESS));
-        BigInteger refundAmount = BigInteger.ONE;
+        Coin refundAmount = Coin.ONE;
         Address refundAddress = new ECKey().toAddress(NETWORK_PARAMS);
         Payment payment = PaymentProtocol.createPaymentMessage(transactions, refundAmount, refundAddress, MEMO,
                 MERCHANT_DATA);
diff --git a/core/src/test/java/com/google/bitcoin/protocols/payments/PaymentSessionTest.java b/core/src/test/java/com/google/bitcoin/protocols/payments/PaymentSessionTest.java
index adc265ed..67163f39 100644
--- a/core/src/test/java/com/google/bitcoin/protocols/payments/PaymentSessionTest.java
+++ b/core/src/test/java/com/google/bitcoin/protocols/payments/PaymentSessionTest.java
@@ -28,7 +28,6 @@ import org.junit.Before;
 import org.junit.Test;
 
 import java.io.InputStream;
-import java.math.BigInteger;
 import java.net.URL;
 import java.util.ArrayList;
 import java.util.Date;
@@ -45,7 +44,7 @@ public class PaymentSessionTest {
     private ECKey serverKey;
     private Transaction tx;
     private TransactionOutput outputToMe;
-    BigInteger nanoCoins = Utils.toNanoCoins(1, 0);
+    Coin nanoCoins = Utils.toNanoCoins(1, 0);
 
     @Before
     public void setUp() throws Exception {
@@ -97,7 +96,7 @@ public class PaymentSessionTest {
                 .setSerializedPaymentDetails(paymentDetails.toByteString())
                 .build();
         MockPaymentSession paymentSession = new MockPaymentSession(paymentRequest);
-        assertEquals(BigInteger.ZERO, paymentSession.getValue());
+        assertEquals(Coin.ZERO, paymentSession.getValue());
         assertNull(paymentSession.getPaymentUrl());
         assertNull(paymentSession.getMemo());
     }
diff --git a/core/src/test/java/com/google/bitcoin/store/WalletProtobufSerializerTest.java b/core/src/test/java/com/google/bitcoin/store/WalletProtobufSerializerTest.java
index 8905b339..46312725 100644
--- a/core/src/test/java/com/google/bitcoin/store/WalletProtobufSerializerTest.java
+++ b/core/src/test/java/com/google/bitcoin/store/WalletProtobufSerializerTest.java
@@ -74,7 +74,7 @@ public class WalletProtobufSerializerTest {
         // Check the base case of a wallet with one key and no transactions.
         Wallet wallet1 = roundTrip(myWallet);
         assertEquals(0, wallet1.getTransactions(true).size());
-        assertEquals(BigInteger.ZERO, wallet1.getBalance());
+        assertEquals(Coin.ZERO, wallet1.getBalance());
         assertArrayEquals(myKey.getPubKey(),
                 wallet1.findKeyFromPubHash(myKey.getPubKeyHash()).getPubKey());
         assertArrayEquals(myKey.getPrivKeyBytes(),
@@ -92,7 +92,7 @@ public class WalletProtobufSerializerTest {
     @Test
     public void oneTx() throws Exception {
         // Check basic tx serialization.
-        BigInteger v1 = Utils.toNanoCoins(1, 0);
+        Coin v1 = Utils.toNanoCoins(1, 0);
         Transaction t1 = createFakeTx(params, v1, myAddress);
         t1.getConfidence().markBroadcastBy(new PeerAddress(InetAddress.getByName("1.2.3.4")));
         t1.getConfidence().markBroadcastBy(new PeerAddress(InetAddress.getByName("5.6.7.8")));
@@ -136,7 +136,7 @@ public class WalletProtobufSerializerTest {
         assertEquals(1, wallet1.getTransactions(true).size());
         Transaction t1 = wallet1.getTransaction(doubleSpends.t1.getHash());
         assertEquals(ConfidenceType.DEAD, t1.getConfidence().getConfidenceType());
-        assertEquals(BigInteger.ZERO, wallet1.getBalance());
+        assertEquals(Coin.ZERO, wallet1.getBalance());
 
         // TODO: Wallet should store overriding transactions even if they are not wallet-relevant.
         // assertEquals(doubleSpends.t2, t1.getConfidence().getOverridingTransaction());
@@ -192,7 +192,7 @@ public class WalletProtobufSerializerTest {
         final ArrayList<Transaction> txns = new ArrayList<Transaction>(2);
         myWallet.addEventListener(new AbstractWalletEventListener() {
             @Override
-            public void onCoinsReceived(Wallet wallet, Transaction tx, BigInteger prevBalance, BigInteger newBalance) {
+            public void onCoinsReceived(Wallet wallet, Transaction tx, Coin prevBalance, Coin newBalance) {
                 txns.add(tx);
             }
         });
@@ -275,7 +275,7 @@ public class WalletProtobufSerializerTest {
     public void testRoundTripNormalWallet() throws Exception {
         Wallet wallet1 = roundTrip(myWallet);     
         assertEquals(0, wallet1.getTransactions(true).size());
-        assertEquals(BigInteger.ZERO, wallet1.getBalance());
+        assertEquals(Coin.ZERO, wallet1.getBalance());
         assertArrayEquals(myKey.getPubKey(),
                 wallet1.findKeyFromPubHash(myKey.getPubKeyHash()).getPubKey());
         assertArrayEquals(myKey.getPrivKeyBytes(),
diff --git a/core/src/test/java/com/google/bitcoin/wallet/DefaultCoinSelectorTest.java b/core/src/test/java/com/google/bitcoin/wallet/DefaultCoinSelectorTest.java
index f6d00b9e..a10ddc8a 100644
--- a/core/src/test/java/com/google/bitcoin/wallet/DefaultCoinSelectorTest.java
+++ b/core/src/test/java/com/google/bitcoin/wallet/DefaultCoinSelectorTest.java
@@ -25,7 +25,6 @@ import org.junit.After;
 import org.junit.Before;
 import org.junit.Test;
 
-import java.math.BigInteger;
 import java.net.InetAddress;
 import java.util.ArrayList;
 
@@ -97,7 +96,7 @@ public class DefaultCoinSelectorTest extends TestWithWallet {
         Transaction t1 = checkNotNull(sendMoneyToWallet(Utils.COIN, AbstractBlockChain.NewBlockType.BEST_CHAIN));
         // Padding block.
         wallet.notifyNewBestBlock(FakeTxBuilder.createFakeBlock(blockStore).storedBlock);
-        final BigInteger TWO_COINS = Utils.COIN.multiply(BigInteger.valueOf(2));
+        final Coin TWO_COINS = Utils.COIN.multiply(Coin.valueOf(2));
         Transaction t2 = checkNotNull(sendMoneyToWallet(TWO_COINS, AbstractBlockChain.NewBlockType.BEST_CHAIN));
         Transaction t3 = checkNotNull(sendMoneyToWallet(Utils.CENT, AbstractBlockChain.NewBlockType.BEST_CHAIN));
 
diff --git a/core/src/test/java/com/google/bitcoin/wallet/DefaultRiskAnalysisTest.java b/core/src/test/java/com/google/bitcoin/wallet/DefaultRiskAnalysisTest.java
index 9b2ff350..c89974f9 100644
--- a/core/src/test/java/com/google/bitcoin/wallet/DefaultRiskAnalysisTest.java
+++ b/core/src/test/java/com/google/bitcoin/wallet/DefaultRiskAnalysisTest.java
@@ -17,8 +17,6 @@
 
 package com.google.bitcoin.wallet;
 
-import java.math.BigInteger;
-
 import com.google.bitcoin.core.*;
 import com.google.bitcoin.params.MainNetParams;
 import com.google.bitcoin.script.ScriptBuilder;
@@ -136,7 +134,7 @@ public class DefaultRiskAnalysisTest {
 
         Transaction dustTx = new Transaction(params);
         dustTx.addInput(params.getGenesisBlock().getTransactions().get(0).getOutput(0));
-        dustTx.addOutput(BigInteger.ONE, key1); // 1 Satoshi
+        dustTx.addOutput(Coin.ONE, key1); // 1 Satoshi
         assertEquals(RiskAnalysis.Result.NON_STANDARD, DefaultRiskAnalysis.FACTORY.create(wallet, dustTx, NO_DEPS).analyze());
 
         Transaction edgeCaseTx = new Transaction(params);
diff --git a/examples/src/main/java/com/google/bitcoin/examples/DoubleSpend.java b/examples/src/main/java/com/google/bitcoin/examples/DoubleSpend.java
index 130f9ac3..d500013e 100644
--- a/examples/src/main/java/com/google/bitcoin/examples/DoubleSpend.java
+++ b/examples/src/main/java/com/google/bitcoin/examples/DoubleSpend.java
@@ -7,7 +7,6 @@ import com.google.bitcoin.utils.BriefLogFormatter;
 import com.google.bitcoin.utils.Threading;
 
 import java.io.File;
-import java.math.BigInteger;
 
 /**
  * This is a little test app that waits for a coin on a local regtest node, then  generates two transactions that double
@@ -28,7 +27,7 @@ public class DoubleSpend {
 
         kit.wallet().getBalanceFuture(Utils.COIN, Wallet.BalanceType.AVAILABLE).get();
         Transaction tx1 = kit.wallet().createSend(new Address(params, "muYPFNCv7KQEG2ZLM7Z3y96kJnNyXJ53wm"), Utils.CENT);
-        Transaction tx2 = kit.wallet().createSend(new Address(params, "muYPFNCv7KQEG2ZLM7Z3y96kJnNyXJ53wm"), Utils.CENT.add(BigInteger.TEN));
+        Transaction tx2 = kit.wallet().createSend(new Address(params, "muYPFNCv7KQEG2ZLM7Z3y96kJnNyXJ53wm"), Utils.CENT.add(Coin.TEN));
         final Peer peer = kit.peerGroup().getConnectedPeers().get(0);
         peer.addEventListener(new AbstractPeerEventListener() {
             @Override
diff --git a/examples/src/main/java/com/google/bitcoin/examples/ExamplePaymentChannelClient.java b/examples/src/main/java/com/google/bitcoin/examples/ExamplePaymentChannelClient.java
index 05853bc4..dbb080d5 100644
--- a/examples/src/main/java/com/google/bitcoin/examples/ExamplePaymentChannelClient.java
+++ b/examples/src/main/java/com/google/bitcoin/examples/ExamplePaymentChannelClient.java
@@ -34,14 +34,13 @@ import org.slf4j.LoggerFactory;
 
 import java.io.File;
 import java.io.IOException;
-import java.math.BigInteger;
 import java.net.InetSocketAddress;
 import java.util.List;
 import java.util.concurrent.CountDownLatch;
 import java.util.concurrent.ExecutionException;
 
+import static com.google.bitcoin.core.Coin.TEN;
 import static com.google.bitcoin.core.Utils.CENT;
-import static java.math.BigInteger.TEN;
 
 /**
  * Simple client that connects to the given host, opens a channel, and pays one cent.
@@ -49,7 +48,7 @@ import static java.math.BigInteger.TEN;
 public class ExamplePaymentChannelClient {
     private static final org.slf4j.Logger log = LoggerFactory.getLogger(ExamplePaymentChannelClient.class);
     private WalletAppKit appKit;
-    private final BigInteger channelSize;
+    private final Coin channelSize;
     private final ECKey myKey;
     private final NetworkParameters params;
 
@@ -124,7 +123,7 @@ public class ExamplePaymentChannelClient {
                 // we are not allowed to have payment channels that pay nothing at all.
                 log.info("Success! Trying to make {} micropayments. Already paid {} satoshis on this channel",
                         times, client.state().getValueSpent());
-                final BigInteger MICROPAYMENT_SIZE = CENT.divide(TEN);
+                final Coin MICROPAYMENT_SIZE = CENT.divide(TEN);
                 for (int i = 0; i < times; i++) {
                     try {
                         // Wait because the act of making a micropayment is async, and we're not allowed to overlap.
@@ -164,11 +163,11 @@ public class ExamplePaymentChannelClient {
         latch.await();
     }
 
-    private void waitForSufficientBalance(BigInteger amount) {
+    private void waitForSufficientBalance(Coin amount) {
         // Not enough money in the wallet.
-        BigInteger amountPlusFee = amount.add(Wallet.SendRequest.DEFAULT_FEE_PER_KB);
+        Coin amountPlusFee = amount.add(Wallet.SendRequest.DEFAULT_FEE_PER_KB);
         // ESTIMATED because we don't really need to wait for confirmation.
-        ListenableFuture<BigInteger> balanceFuture = appKit.wallet().getBalanceFuture(amountPlusFee, Wallet.BalanceType.ESTIMATED);
+        ListenableFuture<Coin> balanceFuture = appKit.wallet().getBalanceFuture(amountPlusFee, Wallet.BalanceType.ESTIMATED);
         if (!balanceFuture.isDone()) {
             System.out.println("Please send " + Utils.bitcoinValueToFriendlyString(amountPlusFee) +
                     " BTC to " + myKey.toAddress(params));
diff --git a/examples/src/main/java/com/google/bitcoin/examples/ExamplePaymentChannelServer.java b/examples/src/main/java/com/google/bitcoin/examples/ExamplePaymentChannelServer.java
index 08ac4386..118c8fc2 100644
--- a/examples/src/main/java/com/google/bitcoin/examples/ExamplePaymentChannelServer.java
+++ b/examples/src/main/java/com/google/bitcoin/examples/ExamplePaymentChannelServer.java
@@ -17,6 +17,7 @@
 
 package com.google.bitcoin.examples;
 
+import com.google.bitcoin.core.Coin;
 import com.google.bitcoin.core.NetworkParameters;
 import com.google.bitcoin.core.Sha256Hash;
 import com.google.bitcoin.core.VerificationException;
@@ -26,10 +27,10 @@ import com.google.bitcoin.params.RegTestParams;
 import com.google.bitcoin.protocols.channels.*;
 import com.google.bitcoin.utils.BriefLogFormatter;
 import com.google.common.collect.ImmutableList;
+
 import org.slf4j.LoggerFactory;
 
 import java.io.File;
-import java.math.BigInteger;
 import java.net.SocketAddress;
 import java.util.List;
 
@@ -71,7 +72,7 @@ public class ExamplePaymentChannelServer implements PaymentChannelServerListener
         // We provide a peer group, a wallet, a timeout in seconds, the amount we require to start a channel and
         // an implementation of HandlerFactory, which we just implement ourselves.
         final int MILLI = 100000;
-        new PaymentChannelServerListener(appKit.peerGroup(), appKit.wallet(), 15, BigInteger.valueOf(MILLI), this).bindAndStart(4242);
+        new PaymentChannelServerListener(appKit.peerGroup(), appKit.wallet(), 15, Coin.valueOf(MILLI), this).bindAndStart(4242);
     }
 
     @Override
@@ -101,7 +102,7 @@ public class ExamplePaymentChannelServer implements PaymentChannelServerListener
             }
 
             @Override
-            public void paymentIncrease(BigInteger by, BigInteger to) {
+            public void paymentIncrease(Coin by, Coin to) {
                 log.info("Client {} paid increased payment by {} for a total of " + to.toString(), clientAddress, by);
             }
 
diff --git a/examples/src/main/java/com/google/bitcoin/examples/ForwardingService.java b/examples/src/main/java/com/google/bitcoin/examples/ForwardingService.java
index 2d91be09..4f54a7da 100644
--- a/examples/src/main/java/com/google/bitcoin/examples/ForwardingService.java
+++ b/examples/src/main/java/com/google/bitcoin/examples/ForwardingService.java
@@ -29,7 +29,6 @@ import com.google.common.util.concurrent.Futures;
 import com.google.common.util.concurrent.MoreExecutors;
 
 import java.io.File;
-import java.math.BigInteger;
 
 import static com.google.common.base.Preconditions.checkNotNull;
 
@@ -81,11 +80,11 @@ public class ForwardingService {
         // We want to know when we receive money.
         kit.wallet().addEventListener(new AbstractWalletEventListener() {
             @Override
-            public void onCoinsReceived(Wallet w, Transaction tx, BigInteger prevBalance, BigInteger newBalance) {
+            public void onCoinsReceived(Wallet w, Transaction tx, Coin prevBalance, Coin newBalance) {
                 // Runs in the dedicated "user thread" (see bitcoinj docs for more info on this).
                 //
                 // The transaction "tx" can either be pending, or included into a block (we didn't see the broadcast).
-                BigInteger value = tx.getValueSentToMe(w);
+                Coin value = tx.getValueSentToMe(w);
                 System.out.println("Received tx for " + Utils.bitcoinValueToFriendlyString(value) + ": " + tx);
                 System.out.println("Transaction will be forwarded after it confirms.");
                 // Wait until it's made it into the block chain (may run immediately if it's already there).
@@ -121,10 +120,10 @@ public class ForwardingService {
 
     private static void forwardCoins(Transaction tx) {
         try {
-            BigInteger value = tx.getValueSentToMe(kit.wallet());
+            Coin value = tx.getValueSentToMe(kit.wallet());
             System.out.println("Forwarding " + Utils.bitcoinValueToFriendlyString(value) + " BTC");
             // Now send the coins back! Send with a small fee attached to ensure rapid confirmation.
-            final BigInteger amountToSend = value.subtract(Transaction.REFERENCE_DEFAULT_MIN_TX_FEE);
+            final Coin amountToSend = value.subtract(Transaction.REFERENCE_DEFAULT_MIN_TX_FEE);
             final Wallet.SendResult sendResult = kit.wallet().sendCoins(kit.peerGroup(), forwardingAddress, amountToSend);
             checkNotNull(sendResult);  // We should never try to send more coins than we have!
             System.out.println("Sending ...");
diff --git a/examples/src/main/java/com/google/bitcoin/examples/RefreshWallet.java b/examples/src/main/java/com/google/bitcoin/examples/RefreshWallet.java
index 7458683d..806a4817 100644
--- a/examples/src/main/java/com/google/bitcoin/examples/RefreshWallet.java
+++ b/examples/src/main/java/com/google/bitcoin/examples/RefreshWallet.java
@@ -23,7 +23,6 @@ import com.google.bitcoin.store.BlockStore;
 import com.google.bitcoin.store.MemoryBlockStore;
 
 import java.io.File;
-import java.math.BigInteger;
 import java.net.InetAddress;
 
 /**
@@ -46,7 +45,7 @@ public class RefreshWallet {
 
         wallet.addEventListener(new AbstractWalletEventListener() {
             @Override
-            public synchronized void onCoinsReceived(Wallet w, Transaction tx, BigInteger prevBalance, BigInteger newBalance) {
+            public synchronized void onCoinsReceived(Wallet w, Transaction tx, Coin prevBalance, Coin newBalance) {
                 System.out.println("\nReceived tx " + tx.getHashAsString());
                 System.out.println(tx.toString());
             }
diff --git a/tools/src/main/java/com/google/bitcoin/tools/TestFeeLevel.java b/tools/src/main/java/com/google/bitcoin/tools/TestFeeLevel.java
index a1f21be3..790e30f5 100644
--- a/tools/src/main/java/com/google/bitcoin/tools/TestFeeLevel.java
+++ b/tools/src/main/java/com/google/bitcoin/tools/TestFeeLevel.java
@@ -8,7 +8,6 @@ import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
 import java.io.File;
-import java.math.BigInteger;
 
 /**
  * A program that sends a transaction with the specified fee and measures how long it takes to confirm.
@@ -26,7 +25,7 @@ public class TestFeeLevel {
             return;
         }
 
-        BigInteger feeToTest = new BigInteger(args[0]);
+        Coin feeToTest = Coin.valueOf(Long.parseLong(args[0]));
 
         kit = new WalletAppKit(PARAMS, new File("."), "testfeelevel");
         kit.startAsync();
@@ -39,7 +38,7 @@ public class TestFeeLevel {
         }
     }
 
-    private static void go(BigInteger feeToTest) throws InterruptedException, java.util.concurrent.ExecutionException, InsufficientMoneyException {
+    private static void go(Coin feeToTest) throws InterruptedException, java.util.concurrent.ExecutionException, InsufficientMoneyException {
         kit.peerGroup().setMaxConnections(50);
 
         final Address address = kit.wallet().currentReceiveKey().toAddress(PARAMS);
diff --git a/tools/src/main/java/com/google/bitcoin/tools/WalletTool.java b/tools/src/main/java/com/google/bitcoin/tools/WalletTool.java
index ead75981..9cd74761 100644
--- a/tools/src/main/java/com/google/bitcoin/tools/WalletTool.java
+++ b/tools/src/main/java/com/google/bitcoin/tools/WalletTool.java
@@ -124,9 +124,9 @@ public class WalletTool {
             value = s;
         }
 
-        public boolean matchBitcoins(BigInteger comparison) {
+        public boolean matchBitcoins(Coin comparison) {
             try {
-                BigInteger units = Utils.toNanoCoins(value);
+                Coin units = Utils.toNanoCoins(value);
                 switch (type) {
                     case LT: return comparison.compareTo(units) < 0;
                     case GT: return comparison.compareTo(units) > 0;
@@ -323,7 +323,7 @@ public class WalletTool {
                     System.err.println("--payment-request and --output cannot be used together.");
                     return;
                 } else if (options.has(outputFlag)) {
-                    BigInteger fee = BigInteger.ZERO;
+                    Coin fee = Coin.ZERO;
                     if (options.has("fee")) {
                         fee = Utils.toNanoCoins((String)options.valueOf("fee"));
                     }
@@ -413,7 +413,7 @@ public class WalletTool {
         }
     }
 
-    private static void send(List<String> outputs, BigInteger fee, String lockTimeStr, boolean allowUnconfirmed) throws VerificationException {
+    private static void send(List<String> outputs, Coin fee, String lockTimeStr, boolean allowUnconfirmed) throws VerificationException {
         try {
             // Convert the input strings to outputs.
             Transaction t = new Transaction(params);
@@ -425,7 +425,7 @@ public class WalletTool {
                 }
                 String destination = parts[0];
                 try {
-                    BigInteger value = Utils.toNanoCoins(parts[1]);
+                    Coin value = Utils.toNanoCoins(parts[1]);
                     if (destination.startsWith("0")) {
                         // Treat as a raw public key.
                         byte[] pubKey = new BigInteger(destination, 16).toByteArray();
@@ -567,7 +567,7 @@ public class WalletTool {
     private static void send(PaymentSession session) {
         try {
             System.out.println("Payment Request");
-            System.out.println("Amount: " + session.getValue().doubleValue() / 100000 + "mBTC");
+            System.out.println("Coin: " + session.getValue().doubleValue() / 100000 + "mBTC");
             System.out.println("Date: " + session.getDate());
             System.out.println("Memo: " + session.getMemo());
             if (session.pkiVerificationData != null) {
@@ -636,15 +636,15 @@ public class WalletTool {
                     }
 
                     @Override
-                    public void onCoinsReceived(Wallet wallet, Transaction tx, BigInteger prevBalance, BigInteger newBalance) {
+                    public void onCoinsReceived(Wallet wallet, Transaction tx, Coin prevBalance, Coin newBalance) {
                         // Runs in a peer thread.
                         super.onCoinsReceived(wallet, tx, prevBalance, newBalance);
                         handleTx(tx);
                     }
 
                     @Override
-                    public void onCoinsSent(Wallet wallet, Transaction tx, BigInteger prevBalance,
-                                            BigInteger newBalance) {
+                    public void onCoinsSent(Wallet wallet, Transaction tx, Coin prevBalance,
+                                            Coin newBalance) {
                         // Runs in a peer thread.
                         super.onCoinsSent(wallet, tx, prevBalance, newBalance);
                         handleTx(tx);
@@ -677,7 +677,7 @@ public class WalletTool {
                     public synchronized void onChange() {
                         super.onChange();
                         saveWallet(walletFile);
-                        BigInteger balance = wallet.getBalance(Wallet.BalanceType.ESTIMATED);
+                        Coin balance = wallet.getBalance(Wallet.BalanceType.ESTIMATED);
                         if (condition.matchBitcoins(balance)) {
                             System.out.println(Utils.bitcoinValueToFriendlyString(balance));
                             latch.countDown();