Embed circuit

Cargo.toml

@@ -44,6 +44,7 @@ proptest = { version = "1.0", optional = true }
 rayon = "1.5.1"
 serde = "1.0"
 sha2 = "0.10.1"
+tempfile = "3.3.0"
 thiserror = "1.0.0"
 tiny-keccak = { version = "2.0.2", optional = true }
 zkp-u256 = { version = "0.2", optional = true }

src/circuit.rs

@@ -0,0 +1,26 @@
+use ark_bn254::{Bn254, Fr};
+use ark_circom::{read_zkey, WitnessCalculator};
+use ark_groth16::ProvingKey;
+use ark_relations::r1cs::ConstraintMatrices;
+use core::include_bytes;
+use once_cell::sync::Lazy;
+use std::io::{Cursor, Write};
+use tempfile::NamedTempFile;
+
+const ZKEY_BYTES: &'static [u8] = include_bytes!("../semaphore/build/snark/semaphore_final.zkey");
+const WASM: &'static [u8] = include_bytes!("../semaphore/build/snark/semaphore.wasm");
+
+pub(crate) static ZKEY: Lazy<(ProvingKey<Bn254>, ConstraintMatrices<Fr>)> = Lazy::new(|| {
+    let mut reader = Cursor::new(ZKEY_BYTES);
+    read_zkey(&mut reader).expect("zkey should be valid")
+});
+
+pub(crate) static WITNESS_CALCULATOR: Lazy<WitnessCalculator> = Lazy::new(|| {
+    // HACK: ark-circom requires a file, so we make one!
+    let mut tmpfile = NamedTempFile::new().expect("Failed to create temp file");
+    tmpfile.write(WASM).expect("Failed to write to temp file");
+    let path = tmpfile.into_temp_path();
+    let result = WitnessCalculator::new(&path).expect("Failed to create witness calculator");
+    path.close().expect("Could not remove tempfile");
+    result
+});

src/lib.rs

@@ -3,6 +3,7 @@
 // TODO: ark-circom and ethers-core pull in a lot of deps, some duplicate.
 #![allow(clippy::multiple_crate_versions)]
 
+mod circuit;
 pub mod hash;
 pub mod identity;
 pub mod merkle_tree;

src/protocol.rs

@@ -1,4 +1,5 @@
 use crate::{
+    circuit::{WITNESS_CALCULATOR, ZKEY},
     identity::Identity,
     merkle_tree::{self, Branch},
     poseidon_tree::PoseidonHash,
@@ -89,11 +90,6 @@ pub fn generate_proof(
     external_nullifier: &[u8],
     signal: &[u8],
 ) -> Result<Proof<Bn<Parameters>>, ProofError> {
-    let mut file = File::open(&config.zkey)?;
-    let (params, matrices) = read_zkey(&mut file)?;
-    let num_inputs = matrices.num_instance_variables;
-    let num_constraints = matrices.num_constraints;
-
     let external_nullifier = hash_external_nullifier(external_nullifier);
     let signal = hash_signal(signal);
     let inputs = [
@@ -117,9 +113,8 @@ pub fn generate_proof(
 
     let now = Instant::now();
 
-    let mut witness = WitnessCalculator::new(&config.wasm).map_err(ProofError::WitnessError)?;
-
-    let full_assignment = witness
+    let full_assignment = WITNESS_CALCULATOR
+        .clone()
         .calculate_witness_element::<Bn254, _>(inputs, false)
         .map_err(ProofError::WitnessError)?;
 
@@ -134,12 +129,12 @@ pub fn generate_proof(
     let now = Instant::now();
 
     let proof = create_proof_with_reduction_and_matrices::<_, CircomReduction>(
-        &params,
+        &ZKEY.0,
         r,
         s,
-        &matrices,
-        num_inputs,
-        num_constraints,
+        &ZKEY.1,
+        ZKEY.1.num_instance_variables,
+        ZKEY.1.num_constraints,
         full_assignment.as_slice(),
     )?;
 
@@ -162,10 +157,7 @@ pub fn verify_proof(
     external_nullifier: &[u8],
     proof: &Proof<Bn<Parameters>>,
 ) -> Result<bool, ProofError> {
-    let mut file = File::open(&config.zkey)?;
-    let (params, _) = read_zkey(&mut file)?;
-
-    let pvk = prepare_verifying_key(&params.vk);
+    let pvk = prepare_verifying_key(&ZKEY.0.vk);
 
     let public_inputs = vec![
         root,