tornado-trees/contracts/verifiers/BatchTreeUpdateVerifier.sol

// SPDX-License-Identifier: MIT

pragma solidity ^0.6.0;

library Pairing {
    uint256 constant PRIME_Q = 21888242871839275222246405745257275088696311157297823662689037894645226208583;

    struct G1Point {
        uint256 X;
        uint256 Y;
    }

    // Encoding of field elements is: X[0] * z + X[1]
    struct G2Point {
        uint256[2] X;
        uint256[2] Y;
    }

    /*
     * @return The negation of p, i.e. p.plus(p.negate()) should be zero
     */
    function negate(G1Point memory p) internal pure returns (G1Point memory) {
        // The prime q in the base field F_q for G1
        if (p.X == 0 && p.Y == 0) {
            return G1Point(0, 0);
        } else {
            return G1Point(p.X, PRIME_Q - (p.Y % PRIME_Q));
        }
    }

    /*
     * @return r the sum of two points of G1
     */
    function plus(
        G1Point memory p1,
        G1Point memory p2
    ) internal view returns (G1Point memory r) {
        uint256[4] memory input = [
            p1.X, p1.Y,
            p2.X, p2.Y
        ];
        bool success;

        // solium-disable-next-line security/no-inline-assembly
        assembly {
            success := staticcall(sub(gas(), 2000), 6, input, 0xc0, r, 0x60)
            // Use "invalid" to make gas estimation work
            switch success case 0 { invalid() }
        }

        require(success, "pairing-add-failed");
    }

    /*
     * @return r the product of a point on G1 and a scalar, i.e.
     *         p == p.scalarMul(1) and p.plus(p) == p.scalarMul(2) for all
     *         points p.
     */
    function scalarMul(G1Point memory p, uint256 s) internal view returns (G1Point memory r) {
        uint256[3] memory input = [p.X, p.Y, s];
        bool success;

        // solium-disable-next-line security/no-inline-assembly
        assembly {
            success := staticcall(sub(gas(), 2000), 7, input, 0x80, r, 0x60)
            // Use "invalid" to make gas estimation work
            switch success case 0 { invalid() }
        }

        require(success, "pairing-mul-failed");
    }

    /* @return The result of computing the pairing check
     *         e(p1[0], p2[0]) *  .... * e(p1[n], p2[n]) == 1
     *         For example,
     *         pairing([P1(), P1().negate()], [P2(), P2()]) should return true.
     */
    function pairing(
        G1Point memory a1,
        G2Point memory a2,
        G1Point memory b1,
        G2Point memory b2,
        G1Point memory c1,
        G2Point memory c2,
        G1Point memory d1,
        G2Point memory d2
    ) internal view returns (bool) {
        uint256[24] memory input = [
            a1.X, a1.Y, a2.X[0], a2.X[1], a2.Y[0], a2.Y[1],
            b1.X, b1.Y, b2.X[0], b2.X[1], b2.Y[0], b2.Y[1],
            c1.X, c1.Y, c2.X[0], c2.X[1], c2.Y[0], c2.Y[1],
            d1.X, d1.Y, d2.X[0], d2.X[1], d2.Y[0], d2.Y[1]
        ];
        uint256[1] memory out;
        bool success;

        // solium-disable-next-line security/no-inline-assembly
        assembly {
            success := staticcall(sub(gas(), 2000), 8, input, mul(24, 0x20), out, 0x20)
            // Use "invalid" to make gas estimation work
            switch success case 0 { invalid() }
        }

        require(success, "pairing-opcode-failed");
        return out[0] != 0;
    }
}

contract BatchTreeUpdateVerifier {
    uint256 constant SNARK_SCALAR_FIELD = 21888242871839275222246405745257275088548364400416034343698204186575808495617;
    uint256 constant PRIME_Q = 21888242871839275222246405745257275088696311157297823662689037894645226208583;
    using Pairing for *;

    struct VerifyingKey {
        Pairing.G1Point alfa1;
        Pairing.G2Point beta2;
        Pairing.G2Point gamma2;
        Pairing.G2Point delta2;
        Pairing.G1Point[2] IC;
    }

    function verifyingKey() internal pure returns (VerifyingKey memory vk) {
        vk.alfa1 = Pairing.G1Point(uint256(20475789791681002364587166738311620805815985969091106757478379420262430093495), uint256(3034180384279528157431123624668892018871098425968640214767822771352219138078));
        vk.beta2 = Pairing.G2Point([uint256(347992840312110670849483472224503623225781749273259516677464742758581199694), uint256(16853081403278411985324640353650047676779142117029386935051386044282804346484)], [uint256(10461241566647602546027012417757263991485755060136522105605550609788790829933), uint256(16049761706815422591462572571571264938897676292217555774707799384732883004386)]);
        vk.gamma2 = Pairing.G2Point([uint256(5535450215937949788522672716791294482208969162172756729752675877422249461391), uint256(4537903555000997751027892507073556632992848536024556182449526590439971414042)], [uint256(6688278057604431581483695896713912024597719708930089928002132340517626404891), uint256(15745439923152020754042431613052318298038129099865656040309120795605091105487)]);
        vk.delta2 = Pairing.G2Point([uint256(10712491908603553476637447918495381165104059355722416702328240143919146641319), uint256(15855442659923189569787773688895011287546687523233653745264460947047886121140)], [uint256(18278088599243830423965796542892879791365910862597475788753708589843343437901), uint256(10765606859348375283724614934374540130725132299795942405716724739350245709734)]);
        vk.IC[0] = Pairing.G1Point(uint256(18147360875100520747353841225428915644191762631193821400291387675910597374366), uint256(17222433096548585553756828362569506045947134360392537102794184064340219776032));
        vk.IC[1] = Pairing.G1Point(uint256(3514632146136652297064638325657684436433185732623721288055192259268961814948), uint256(8363257337389338977321440370428118205387545635573906956020792115766452976369));

    }

    /*
     * @returns Whether the proof is valid given the hardcoded verifying key
     *          above and the public inputs
     */
    function verifyProof(
        bytes memory proof,
        uint256[1] memory input
    ) public view returns (bool) {
        uint256[8] memory p = abi.decode(proof, (uint256[8]));
        for (uint8 i = 0; i < p.length; i++) {
            // Make sure that each element in the proof is less than the prime q
            require(p[i] < PRIME_Q, "verifier-proof-element-gte-prime-q");
        }
        Pairing.G1Point memory proofA = Pairing.G1Point(p[0], p[1]);
        Pairing.G2Point memory proofB = Pairing.G2Point([p[2], p[3]], [p[4], p[5]]);
        Pairing.G1Point memory proofC = Pairing.G1Point(p[6], p[7]);

        VerifyingKey memory vk = verifyingKey();
        // Compute the linear combination vkX
        Pairing.G1Point memory vkX = vk.IC[0];
        for (uint256 i = 0; i < input.length; i++) {
            // Make sure that every input is less than the snark scalar field
            require(input[i] < SNARK_SCALAR_FIELD, "verifier-input-gte-snark-scalar-field");
            vkX = Pairing.plus(vkX, Pairing.scalarMul(vk.IC[i + 1], input[i]));
        }

        return Pairing.pairing(
            Pairing.negate(proofA),
            proofB,
            vk.alfa1,
            vk.beta2,
            vkX,
            vk.gamma2,
            proofC,
            vk.delta2
        );
    }
}