Merge pull request #4 from ebfull/zksnark-param-loading

Support loading zk-SNARK parameters

Cargo.lock

@@ -114,6 +114,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 name = "librustzcash"
 version = "0.1.0"
 dependencies = [
+ "bellman 0.1.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "lazy_static 1.0.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "libc 0.2.40 (registry+https://github.com/rust-lang/crates.io-index)",
  "pairing 0.14.1 (registry+https://github.com/rust-lang/crates.io-index)",

Cargo.toml

@@ -12,6 +12,7 @@ crate-type = ["staticlib"]
 libc = "0.2"
 pairing = "0.14.1"
 lazy_static = "1"
+bellman = "0.1"
 
 [dependencies.sapling-crypto]
 git = "https://github.com/zcash-hackworks/sapling-crypto"

include/librustzcash.h

@@ -6,6 +6,14 @@
 extern "C" {
     uint64_t librustzcash_xor(uint64_t a, uint64_t b);
 
+    /// Loads the zk-SNARK parameters into memory and saves
+    /// paths as necessary. Only called once.
+    void librustzcash_init_zksnark_params(
+        const char* spend_path,
+        const char* output_path,
+        const char* sprout_path
+    );
+
     /// Writes the "uncommitted" note value for empty leaves
     /// of the merkle tree. `result` must be a valid pointer
     /// to 32 bytes which will be written.

src/rustzcash.rs

@@ -1,42 +1,89 @@
+extern crate bellman;
 extern crate libc;
-extern crate sapling_crypto;
 extern crate pairing;
+extern crate sapling_crypto;
 
 #[macro_use]
 extern crate lazy_static;
 
-use pairing::{
-    BitIterator,
-    PrimeFieldRepr,
-    PrimeField,
-    bls12_381::{
-        Bls12,
-        Fr,
-        FrRepr
-    }
-};
+use pairing::{BitIterator, PrimeField, PrimeFieldRepr, bls12_381::{Bls12, Fr, FrRepr}};
 
-use sapling_crypto::{
-    jubjub::JubjubBls12,
-    pedersen_hash::{
-        pedersen_hash,
-        Personalization
-    }
-};
+use sapling_crypto::{jubjub::JubjubBls12, pedersen_hash::{pedersen_hash, Personalization}};
 
-use libc::{uint64_t, size_t, c_uchar};
+use bellman::groth16::{prepare_verifying_key, Parameters, PreparedVerifyingKey, VerifyingKey};
+
+use libc::{c_char, c_uchar, size_t, uint64_t};
+use std::ffi::CStr;
+use std::fs::File;
 
 lazy_static! {
-    static ref JUBJUB: JubjubBls12 = {
-        JubjubBls12::new()
-    };
+    static ref JUBJUB: JubjubBls12 = { JubjubBls12::new() };
+}
+
+static mut SAPLING_SPEND_VK: Option<PreparedVerifyingKey<Bls12>> = None;
+static mut SAPLING_OUTPUT_VK: Option<PreparedVerifyingKey<Bls12>> = None;
+static mut SPROUT_GROTH16_VK: Option<PreparedVerifyingKey<Bls12>> = None;
+
+static mut SAPLING_SPEND_PARAMS: Option<Parameters<Bls12>> = None;
+static mut SAPLING_OUTPUT_PARAMS: Option<Parameters<Bls12>> = None;
+static mut SPROUT_GROTH16_PARAMS_PATH: Option<String> = None;
+
+#[no_mangle]
+pub extern "system" fn librustzcash_init_zksnark_params(
+    spend_path: *const c_char,
+    output_path: *const c_char,
+    sprout_path: *const c_char,
+) {
+    // These should be valid CStr's, but the decoding may fail on Windows
+    // so we may need to use OSStr or something.
+    let spend_path = unsafe { CStr::from_ptr(spend_path) }
+        .to_str()
+        .expect("parameter path encoding error")
+        .to_string();
+    let output_path = unsafe { CStr::from_ptr(output_path) }
+        .to_str()
+        .expect("parameter path encoding error")
+        .to_string();
+    let sprout_path = unsafe { CStr::from_ptr(sprout_path) }
+        .to_str()
+        .expect("parameter path encoding error")
+        .to_string();
+
+    // Load from each of the paths
+    let mut spend_fs = File::open(spend_path).expect("couldn't load Sapling spend parameters file");
+    let mut output_fs =
+        File::open(output_path).expect("couldn't load Sapling output parameters file");
+    let mut sprout_fs =
+        File::open(&sprout_path).expect("couldn't load Sprout groth16 parameters file");
+
+    // Deserialize params
+    let spend_params = Parameters::<Bls12>::read(&mut spend_fs, false)
+        .expect("couldn't deserialize Sapling spend parameters file");
+    let output_params = Parameters::<Bls12>::read(&mut output_fs, false)
+        .expect("couldn't deserialize Sapling spend parameters file");
+    let sprout_vk = VerifyingKey::<Bls12>::read(&mut sprout_fs)
+        .expect("couldn't deserialize Sprout Groth16 verifying key");
+
+    // Prepare verifying keys
+    let spend_vk = prepare_verifying_key(&spend_params.vk);
+    let output_vk = prepare_verifying_key(&output_params.vk);
+    let sprout_vk = prepare_verifying_key(&sprout_vk);
+
+    // Caller is responsible for calling this function once, so
+    // these global mutations are safe.
+    unsafe {
+        SAPLING_SPEND_PARAMS = Some(spend_params);
+        SAPLING_OUTPUT_PARAMS = Some(output_params);
+        SPROUT_GROTH16_PARAMS_PATH = Some(sprout_path);
+
+        SAPLING_SPEND_VK = Some(spend_vk);
+        SAPLING_OUTPUT_VK = Some(output_vk);
+        SPROUT_GROTH16_VK = Some(sprout_vk);
+    }
 }
 
 #[no_mangle]
-pub extern "system" fn librustzcash_tree_uncommitted(
-    result: *mut [c_uchar; 32]
-)
-{
+pub extern "system" fn librustzcash_tree_uncommitted(result: *mut [c_uchar; 32]) {
     let tmp = sapling_crypto::primitives::Note::<Bls12>::uncommitted().into_repr();
 
     // Should be okay, caller is responsible for ensuring the pointer
@@ -52,8 +99,7 @@ pub extern "system" fn librustzcash_merkle_hash(
     a: *const [c_uchar; 32],
     b: *const [c_uchar; 32],
     result: *mut [c_uchar; 32],
-)
-{
+) {
     let mut a_repr = FrRepr::default();
     let mut b_repr = FrRepr::default();
 
@@ -77,14 +123,17 @@ pub extern "system" fn librustzcash_merkle_hash(
     for (a, b) in rhs.iter_mut().rev().zip(BitIterator::new(b_repr)) {
         *a = b;
     }
-    
+
     let tmp = pedersen_hash::<Bls12, _>(
         Personalization::MerkleTree(depth),
-        lhs.iter().map(|&x| x)
+        lhs.iter()
+            .map(|&x| x)
             .take(Fr::NUM_BITS as usize)
             .chain(rhs.iter().map(|&x| x).take(Fr::NUM_BITS as usize)),
-        &JUBJUB
-    ).into_xy().0.into_repr();
+        &JUBJUB,
+    ).into_xy()
+        .0
+        .into_repr();
 
     // Should be okay, caller is responsible for ensuring the pointer
     // is a valid pointer to 32 bytes that can be mutated.
@@ -97,12 +146,14 @@ pub extern "system" fn librustzcash_merkle_hash(
 /// as a temporary mechanism for introducing Rust into
 /// Zcash.
 #[no_mangle]
-pub extern "system" fn librustzcash_xor(a: uint64_t, b: uint64_t) -> uint64_t
-{
+pub extern "system" fn librustzcash_xor(a: uint64_t, b: uint64_t) -> uint64_t {
     a ^ b
 }
 
 #[test]
 fn test_xor() {
-    assert_eq!(librustzcash_xor(0x0f0f0f0f0f0f0f0f, 0x1111111111111111), 0x1e1e1e1e1e1e1e1e);
+    assert_eq!(
+        librustzcash_xor(0x0f0f0f0f0f0f0f0f, 0x1111111111111111),
+        0x1e1e1e1e1e1e1e1e
+    );
 }