Merge pull request #22 from appliedzkp/refactor/signal-hash

refactor: create signal hash fun for each protocol

packages/protocols/src/index.ts

@@ -1,7 +1,7 @@
 import { MerkleProof } from "@zk-kit/incremental-merkle-tree"
 import RLN from "./rln"
 import Semaphore from "./semaphore"
-import { generateMerkleProof, generateMerkleTree, genExternalNullifier, genSignalHash } from "./utils"
+import { generateMerkleProof, generateMerkleTree, genExternalNullifier } from "./utils"
 
-export { Semaphore, RLN, generateMerkleProof, generateMerkleTree, genExternalNullifier, genSignalHash, MerkleProof }
+export { Semaphore, RLN, generateMerkleProof, generateMerkleTree, genExternalNullifier, MerkleProof }
 export * from "./types"

packages/protocols/src/rln.ts

@@ -1,8 +1,11 @@
+import { hexlify } from "@ethersproject/bytes"
+import { keccak256 } from "@ethersproject/solidity"
+import { toUtf8Bytes } from "@ethersproject/strings"
 import { MerkleProof } from "@zk-kit/incremental-merkle-tree"
 import { poseidon } from "circomlibjs"
 import { groth16 } from "snarkjs"
 import { RLNFullProof, StrBigInt } from "./types"
-import { Fq, genSignalHash } from "./utils"
+import { Fq } from "./utils"
 
 export default class RLN {
   /**
@@ -73,7 +76,7 @@ export default class RLN {
       identity_secret: identitySecret,
       path_elements: merkleProof.siblings,
       identity_path_index: merkleProof.pathIndices,
-      x: shouldHash ? genSignalHash(signal) : signal,
+      x: shouldHash ? RLN.genSignalHash(signal) : signal,
       epoch,
       rln_identifier: rlnIdentifier
     }
@@ -105,6 +108,17 @@ export default class RLN {
     return poseidon([a1, rlnIdentifier])
   }
 
+  /**
+   * Hashes a signal string with Keccak256.
+   * @param signal The RLN signal.
+   * @returns The signal hash.
+   */
+  public static genSignalHash(signal: string): bigint {
+    const converted = hexlify(toUtf8Bytes(signal))
+
+    return BigInt(keccak256(["bytes"], [converted])) >> BigInt(8)
+  }
+
   /**
    * When spam occurs, identity secret can be retrieved
    * @param x1 x1

packages/protocols/src/semaphore.ts

@@ -1,8 +1,9 @@
+import { keccak256 } from "@ethersproject/solidity"
+import { formatBytes32String } from "@ethersproject/strings"
 import { MerkleProof } from "@zk-kit/incremental-merkle-tree"
 import { poseidon } from "circomlibjs"
 import { groth16 } from "snarkjs"
 import { Proof, SemaphoreFullProof, SemaphoreSolidityProof, SemaphoreWitness, StrBigInt } from "./types"
-import { genSignalHash } from "./utils"
 
 export default class Semaphore {
   /**
@@ -62,8 +63,7 @@ export default class Semaphore {
     identityNullifier: StrBigInt,
     merkleProof: MerkleProof,
     externalNullifier: StrBigInt,
-    signal: string,
-    shouldHash = true
+    signal: string
   ): SemaphoreWitness {
     return {
       identityNullifier,
@@ -71,7 +71,7 @@ export default class Semaphore {
       treePathIndices: merkleProof.pathIndices,
       treeSiblings: merkleProof.siblings,
       externalNullifier,
-      signalHash: shouldHash ? genSignalHash(signal) : signal
+      signalHash: Semaphore.genSignalHash(signal)
     }
   }
 
@@ -85,6 +85,15 @@ export default class Semaphore {
     return poseidon([BigInt(externalNullifier), BigInt(identityNullifier)])
   }
 
+  /**
+   * Hashes a signal string with Keccak256.
+   * @param signal The Semaphore signal.
+   * @returns The signal hash.
+   */
+  public static genSignalHash(signal: string): bigint {
+    return BigInt(keccak256(["bytes32"], [formatBytes32String(signal)])) >> BigInt(8)
+  }
+
   /**
    * Converts a full proof in a proof compatible with the Verifier.sol method inputs.
    * @param fullProof The proof generated with SnarkJS.

packages/protocols/src/utils.ts

@@ -1,6 +1,4 @@
-import { hexlify } from "@ethersproject/bytes"
 import { keccak256 } from "@ethersproject/solidity"
-import { toUtf8Bytes } from "@ethersproject/strings"
 import { IncrementalMerkleTree, MerkleProof } from "@zk-kit/incremental-merkle-tree"
 import { poseidon } from "circomlibjs"
 import { ZqField } from "ffjavascript"
@@ -10,12 +8,6 @@ export const SNARK_FIELD_SIZE = BigInt("2188824287183927522224640574525727508854
 
 export const Fq = new ZqField(SNARK_FIELD_SIZE)
 
-export function genSignalHash(signal: string): bigint {
-  const converted = hexlify(toUtf8Bytes(signal))
-
-  return BigInt(keccak256(["bytes"], [converted])) >> BigInt(8)
-}
-
 export function genExternalNullifier(plaintext: string): string {
   const hashed = keccak256(["string"], [plaintext])
   const hexStr = `0x${hashed.slice(8)}`

packages/protocols/tests/rln.test.ts

@@ -3,7 +3,7 @@ import { getCurveFromName } from "ffjavascript"
 import * as fs from "fs"
 import * as path from "path"
 import { RLN } from "../src"
-import { generateMerkleProof, genExternalNullifier, genSignalHash } from "../src/utils"
+import { generateMerkleProof, genExternalNullifier } from "../src/utils"
 
 describe("RLN", () => {
   const zkeyFiles = "./packages/protocols/zkeyFiles"
@@ -62,9 +62,9 @@ describe("RLN", () => {
       const secretHash = identity.getSecretHash()
 
       const signal1 = "hey hey"
-      const signalHash1 = genSignalHash(signal1)
+      const signalHash1 = RLN.genSignalHash(signal1)
       const signal2 = "hey hey again"
-      const signalHash2 = genSignalHash(signal2)
+      const signalHash2 = RLN.genSignalHash(signal2)
 
       const epoch = genExternalNullifier("test-epoch")
       const rlnIdentifier = RLN.genIdentifier()