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HDW: Add some docs and a safety check to HDKeyDerivation.

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Mike Hearn 2013-11-24 23:59:42 +01:00
parent 8769773717
commit a5d14ba45b
1 changed files with 4 additions and 1 deletions
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5
core/src/main/java/com/google/bitcoin/crypto/HDKeyDerivation.java
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@ -39,11 +39,14 @@ public final class HDKeyDerivation {
/** /**
* Generates a new deterministic key from the given seed, which can be any arbitrary byte array. However resist * Generates a new deterministic key from the given seed, which can be any arbitrary byte array. However resist
* the temptation to use a string as the seed - any key derived from a password is likely to be weak and easily * the temptation to use a string as the seed - any key derived from a password is likely to be weak and easily
* broken by attackers (this is not theoretical, people have had money stolen that way). * broken by attackers (this is not theoretical, people have had money stolen that way). This method checks
* that the given seed is at least 64 bits long.
* *
* @throws HDDerivationException if generated master key is invalid (private key 0 or >= n). * @throws HDDerivationException if generated master key is invalid (private key 0 or >= n).
* @throws IllegalArgumentException if the seed is less than 8 bytes and could be brute forced.
*/ */
public static DeterministicKey createMasterPrivateKey(byte[] seed) throws HDDerivationException { public static DeterministicKey createMasterPrivateKey(byte[] seed) throws HDDerivationException {
checkArgument(seed.length > 8, "Seed is too short and could be brute forced");
// Calculate I = HMAC-SHA512(key="Bitcoin seed", msg=S) // Calculate I = HMAC-SHA512(key="Bitcoin seed", msg=S)
byte[] i = HDUtils.hmacSha512(MASTER_HMAC_SHA512, seed); byte[] i = HDUtils.hmacSha512(MASTER_HMAC_SHA512, seed);
// Split I into two 32-byte sequences, Il and Ir. // Split I into two 32-byte sequences, Il and Ir.