Identity.sol

// SPDX-License-Identifier: MIT
pragma solidity >=0.8.23 <=0.8.29;

import { PoseidonT3 } from "poseidon-solidity/PoseidonT3.sol";
import { PoseidonT6 } from "poseidon-solidity/PoseidonT6.sol";
import { CurveBabyJubJub } from "src/utils/CurveBabyJubJub.sol";
// import { LibString } from "solady/Milady.sol";
// import { Vm } from "forge-std/Vm.sol";
// import { console } from "forge-std/console.sol";

library Identity {
    uint256 internal constant base8x = CurveBabyJubJub.Base8x;
    uint256 internal constant base8y = CurveBabyJubJub.Base8y;

    function getCommitment(bytes memory pubKey) public pure returns (uint256 cmt) {
        (uint256 pkX, uint256 pkY) = abi.decode(pubKey, (uint256, uint256));
        cmt = PoseidonT3.hash([pkX, pkY]);
    }

    // function verifySignatureFFI(bytes32 message, bytes memory signature) public returns (bool) {
    //     (uint256 pkX, uint256 pkY, uint256 s0, uint256 s1, uint256 s2) =
    //         abi.decode(signature, (uint256, uint256, uint256, uint256, uint256));

    //     Vm constant vm = Vm(address(uint160(uint256(keccak256("hevm cheat code")))));

    //     string[] memory inputs = new string[](6);
    //     inputs[0] = "pnpm";
    //     inputs[1] = "semaphore-identity";
    //     inputs[2] = "verify";
    //     inputs[3] = vm.toString(abi.encodePacked(pkX, pkY));
    //     inputs[4] = vm.toString(message);
    //     inputs[5] = vm.toString(abi.encodePacked(s0, s1, s2));

    //     bytes memory res = vm.ffi(inputs);
    //     string memory resStr = string(res);
    //     return LibString.eq(resStr, "true");
    // }

    function verifySignature(bytes32 message, bytes memory signature) public view returns (bool) {
        // Implement eddsa-poseidon verifySignature() method in solidity.
        // https://github.com/privacy-scaling-explorations/zk-kit/blob/388f72b7a029a14bf5c20861d5f54bdaa98b3ac7/packages/eddsa-poseidon/src/eddsa-poseidon-factory.ts#L127-L158
        (uint256 pkX, uint256 pkY, uint256 s0, uint256 s1, uint256 s2) =
            abi.decode(signature, (uint256, uint256, uint256, uint256, uint256));

        uint256 hm = PoseidonT6.hash([s0, s1, pkX, pkY, uint256(message)]);

        (uint256 pLeftx, uint256 pLefty) = CurveBabyJubJub.pointMul(base8x, base8y, s2);

        // This is suppose to be: CurveBabyJubJub.pointMul(pkX, pkY, mulmod(8, hm, FM)),
        //   but I'm not sure the field modulo to use. No, not `CurveBabyJubJub.Q`.
        (uint256 pRightx, uint256 pRighty) = CurveBabyJubJub.pointMul(pkX, pkY, hm);
        (pRightx, pRighty) = CurveBabyJubJub.pointAdd(pRightx, pRighty, pRightx, pRighty);
        (pRightx, pRighty) = CurveBabyJubJub.pointAdd(pRightx, pRighty, pRightx, pRighty);
        (pRightx, pRighty) = CurveBabyJubJub.pointAdd(pRightx, pRighty, pRightx, pRighty);

        (uint256 pSumx, uint256 pSumy) = CurveBabyJubJub.pointAdd(s0, s1, pRightx, pRighty);

        return (pLeftx == pSumx && pLefty == pSumy);
    }
}