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Hydra S1 Proving scheme

Implementations of Hydra S1 prover (js/ts) and verifiers (js/ts/Solidity)

Made by Sismo

Installation

$ yarn add @sismo-core/hydra-s1

Prover js (HydraS1Prover) 

const prover = new HydraS1Prover(
    registryTree,
    commitmentMapperPubKey,
    // + Optional override of the circuit path for ES module (see below for more information)
    {
        wasmPath: "https://[Your server].hydra-s1.wasm",
        zkeyPath: "https://[Your server].hydra-s1.zkey"
    }
);
Params Type Description
registryTree MerkleTree Registry Merkle tree that contain the Accounts Merkle tree
commitmentMapperPubKey EddsaPublicKey Pub key of the CommitmentMapper

To generate the proof, we need to provide a .wasm and a .zkey to the witness calculator. For CommonJS modules we add these files directly in the package and we resolve the path. For ES module we can't do that, that's why we choose to host files on an S3.

If this solution doesn't suite you or if you want to optimize the download time, you can override S3 paths by adding a third params in the HydraS1Prover constructor and host files wherever you want.

ES modules (which can be overridden)

export const wasmPath = "https://static.sismo.io/hydra-s1-zkps/hydra-s1.wasm";
export const zkeyPath = "https://static.sismo.io/hydra-s1-zkps/hydra-s1.zkey";

CommonJS

export const wasmPath = require.resolve('./hydra-s1.wasm');
export const zkeyPath = require.resolve('./hydra-s1.zkey');

Generate Snark Proof

const source: HydraS1Account = {
    identifier: address,
    secret,
    commitmentReceipt
}

const destination: HydraS1Account = {
    identifier: address,
    secret,
    commitmentReceipt
}

const params = {
    source,
    destination,
    claimedValue,
    chainId,
    accountsTree,
    externalNullifier,
    isStrict
}

const snarkProof = await prover.generateSnarkProof(params);

// Generate inputs
// This function is automatically called by generateSnarkProof but you can call it in your tests
const { privateInputs, publicInputs } = await prover.generateInputs(params);

// Throw human readable errors
// This function is automatically called by generateSnarkProof but you can call it in your tests
try {
    await prover.userParamsValidation(params);
} catch (e) {
    console.log(e);
}
Params Type Description
source HydraS1Account Source account
destination HydraS1Account Destination account
claimedValue BigNumberish Must be 0 <= claimedValue <= accountValue if isStrict is false or claimedValue = accountValue if isStrict is true
chainId BigNumberish Chain id
accountsTree MerkleTree Merkle tree constituted which include the source and a value
externalNullifier BigNumberish nullifier = hash((hash(source.secret, 1), externalNullifier)
isStrict boolean Define if the value is strict or not 
export type HydraS1Account = { 
  identifier: BigNumberish,
  secret: BigNumberish,
  commitmentReceipt: [BigNumberish, BigNumberish, BigNumberish]
};

Complete test example

import { CommitmentMapperTester, OWNERSHIP_SIGNATURE_MESSAGE } from "@sismo-core/commitment-mapper-tester-js"; 
import { SnarkProof, REGISTRY_TREE_HEIGHT, HydraS1Prover, HydraS1Account, buildPoseidon, MerkleTree, MerkleTreeData } from "@sismo-core/hydra-s1";
import { BigNumber } from "ethers";


const poseidon = await buildPoseidon();
const commitmentMapperTester = await CommitmentMapperTester.generate();

const sourceAddress = ; //ETHAddress
const sourceSignature = ; //ETHSig(OWNERSHIP_SIGNATURE_MESSAGE)
const sourceSecret = BigNumber.from(1);
const sourceCommitment = poseidon([sourceSecret]).toHexString();
const { commitmentReceipt: sourceCommitmentReceipt } = await commitmentMapperTester.commit(
    sourceAddress,
    sourceSignature,
    sourceCommitment
);

const source: HydraS1Account = {
    identifier: sourceAddress,
    secret: sourceSecret,
    commitmentReceipt: sourceCommitmentReceipt
}

const destinationAddress = ; //ETHAddress
const destinationSignature = ; //ETHSig(OWNERSHIP_SIGNATURE_MESSAGE)
const destinationSecret = BigNumber.from(2);
const destinationCommitment = poseidon([destinationSecret]).toHexString();
const { commitmentReceipt: destinationCommitmentReceipt } = await commitmentMapperTester.commit(
    destinationAddress,
    destinationSignature,
    destinationCommitment
);

const destination: HydraS1Account = {
    identifier: destinationAddress,
    secret: destinationSecret,
    commitmentReceipt: destinationCommitmentReceipt
}

const merkleTreeData: MerkleTreeData = {
    [sourceAddress]: 4,
    "0x01": 5,
    "0x02": 6,
    "0x03": 7
};

const accountsTree = new MerkleTree(merkleTreeData, poseidon);

const registryTree = new MerkleTree({
    [accountsTree.getRoot().toHexString()]: accountsTree.getHeight(),
}, poseidon, REGISTRY_TREE_HEIGHT);

const prover = new HydraS1Prover(
    registryTree,
    await commitmentMapperTester.getPubKey()
); 

const isStrict = true;
const claimedValue = BigNumber.from(merkleTreeData[sourceAddress]);
const chainId = 1;
const externalNullifier = BigNumber.from(123);

const snarkProof: SnarkProof = await prover.generateSnarkProof({
    source,
    destination,
    claimedValue,
    chainId,
    accountsTree,
    externalNullifier,
    isStrict
});

Verifier js (HydraS1Verifier) 

import { HydraS1Verifier } from "@sismo-core/hydra-s1";

const isValid = await HydraS1Verifier.verifyProof(snarkProof.a, snarkProof.b, snarkProof.c, snarkProof.input);

Verifier contract (HydraS1Verifier)

import {HydraS1Verifier} from "@sismo-core/hydra-s1/contracts/HydraS1Verifier.sol";

struct ZKProof {
    uint256[2] a;
    uint256[2][2] b;
    uint256[2] c; 
    uint256[10] input; 
}

contract HydraS1Attester {
    HydraS1Verifier internal _verifier;

    error InvalidSnarkProof(uint256[10] publicInputs);

    constructor(
        HydraS1Verifier hydraS1Verifier
    ) {
        _verifier = hydraS1Verifier;
    }

    function attest(ZKProof calldata proof) external {
        if(! _verifier.verifyProof(proof.a, proof.b, proof.c, proof.input)) {
            revert InvalidSnarkProof(proof.input);
        }
    }
}

License

Distributed under the MIT License.

Contribute

Please, feel free to open issues, PRs or simply provide feedback!

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