3

I need to build an application that uses bilinear pairing operations for generating signatures. If I send a message with its signature to Ethereum, can Ethereum verify this message? Does the EVM support pairing operations?

This is an example of signature verification using BLS signature:

Given a signature S and a public key g^{x}, we verify that e(S ,g)=e(H(m),g^{x}).

3

Yes, at address 0x8 the EVM has a precompiled contract for optimal ate pairing check on the elliptic curve alt_bn128 described in EIP 197.

How can we verify BGLS aggregate signatures in Solidity? has a gist containing the following code which may be useful:

pragma solidity ^0.4.14;

/*
Example of how to verify BLS signatures and BGLS aggregate signatures in Ethereum.

Signatures are generated using https://github.com/Project-Arda/bgls
Code is based on https://github.com/jstoxrocky/zksnarks_example
*/

contract BLSExample {
    struct G1Point {
        uint X;
        uint Y;
    }
    // Encoding of field elements is: X[0] * z + X[1]
    struct G2Point {
        uint[2] X;
        uint[2] Y;
    }

    /// @return the generator of G1
    function P1() internal returns (G1Point) {
        return G1Point(1, 2);
    }

    /// @return the generator of G2
    function P2() internal returns (G2Point) {
        return G2Point(
            [11559732032986387107991004021392285783925812861821192530917403151452391805634,
            10857046999023057135944570762232829481370756359578518086990519993285655852781],

            [4082367875863433681332203403145435568316851327593401208105741076214120093531,
            8495653923123431417604973247489272438418190587263600148770280649306958101930]
        );
    }

    //Example of BLS signature verification
    function verifyBLSTest() returns (bool) {

        bytes memory message = hex"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";

        G1Point memory signature = G1Point(11181692345848957662074290878138344227085597134981019040735323471731897153462, 6479746447046570360435714249272776082787932146211764251347798668447381926167);

        G2Point memory v = G2Point(
            [18523194229674161632574346342370534213928970227736813349975332190798837787897, 5725452645840548248571879966249653216818629536104756116202892528545334967238],
            [3816656720215352836236372430537606984911914992659540439626020770732736710924, 677280212051826798882467475639465784259337739185938192379192340908771705870]
        );

        G1Point memory h = hashToG1(message);

        return pairing2(negate(signature), P2(), h, v);
    }

    //Example of BGLS signature verification with 2 signers
    //Note that the messages differ in their last character.
    function verifyBGLS2() returns (bool) {

        uint numberOfSigners = 2;

        G1Point memory signature = G1Point(7985250684665362734034207174567341000146996823387166378141631317099216977152, 5471024627060516972461571110176333017668072838695251726406965080926450112048);

        bytes memory message0 = hex"7b0a2020226f70656e223a207b0a20202020227072696365223a2039353931372c0a202020202274696d65223a207b0a20202020202022756e6978223a20313438333134323430302c0a2020202020202269736f223a2022323031362d31322d33315430303a30303a30302e3030305a220a202020207d0a20207d2c0a202022636c6f7365223a207b0a20202020227072696365223a2039363736302c0a202020202274696d65223a207b0a20202020202022756e6978223a20313438333232383830302c0a2020202020202269736f223a2022323031372d30312d30315430303a30303a30302e3030305a220a202020207d0a20207d2c0a2020226c6f6f6b7570223a207b0a20202020227072696365223a2039363736302c0a20202020226b223a20312c0a202020202274696d65223a207b0a20202020202022756e6978223a20313438333232383830302c0a2020202020202269736f223a2022323031372d30312d30315430303a30303a30302e3030305a220a202020207d0a20207d0a7d0a6578616d706c652e636f6d2f6170692f30";
        bytes memory message1 = hex"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";

        G2Point memory v0 = G2Point(
            [15516709285352539082439213720585739724329002971882390582209636960597958801449, 19324541677661060388134143597417835654030498723817274130329567224531700170734],
            [16550775633156536193089672538964908973667410921848053632462693002610771214528, 10154483139478025296468271477739414260393126999813603835827647034319242387010]
        );

        G2Point memory v1 = G2Point(
            [14125383697019450293340447180826714775062600193406387386692146468060627933203, 10886345395648455940547500614900453787797209052692168129177801883734751834552],
            [13494666809312056575532152175382485778895768300692817869062640713829304801648, 10580958449683540742032499469496205826101096579572266360455646078388895706251]
        );

        G1Point memory h0 = hashToG1(message0);
        G1Point memory h1 = hashToG1(message1);

        G1Point[] memory a = new G1Point[](numberOfSigners + 1);
        G2Point[] memory b = new G2Point[](numberOfSigners + 1);
        a[0] = negate(signature);
        a[1] = h0;
        a[2] = h1;
        b[0] = P2();
        b[1] = v0;
        b[2] = v1;

        return pairing(a, b);
    }

    //Example of BGLS signature verification with 3 signers
    //Note that the messages differ in their last character.
    function verifyBGLS3() returns (bool) {

        uint numberOfSigners = 3;

        G1Point memory signature = G1Point(385846518441062319503502284295243290270560187383398932887791670182362540842, 19731933537428695151702009864745685458233056709189425720845387511061953267292);

        bytes memory message0 = hex"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";
        bytes memory message1 = hex"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";
        bytes memory message2 = hex"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";

        G2Point memory v0 = G2Point(
            [1787282038370667094324364195810339512415273589223814213215040505578200405366, 414568866548933554513940840943382696902163788831396286279770126458218272940],
            [6560020551439455112781785895092032589010633560844445112872109862153018855017, 19411093226570397520343120724285433000937737461010544490862811136406407315543]
        );

        G2Point memory v1 = G2Point(
            [14831125462625540363404323739936082597729714855858291605999144010730542058037, 8342129546329626371616639780890580451066604883761980695690870205390518348707],
            [808186590373043742842665711030588185456231663895663328011864547134240543671, 1856705676948889458735296604372981546875220644939188415241687241562401814459]
        );

        G2Point memory v2 = G2Point(
            [12507030828714819990408995725310388936101611986473926829733453468215798265704, 16402225253711577242710704509153100189802817297679524801952098990526969620006],
            [18717845356690477533392378472300056893077745517009561191866660997312973511514, 20124563173642533900823905467925868861151292863229012000403558815142682516349]
        );

        G1Point memory h0 = hashToG1(message0);
        G1Point memory h1 = hashToG1(message1);
        G1Point memory h2 = hashToG1(message2);

        G1Point[] memory a = new G1Point[](numberOfSigners + 1);
        G2Point[] memory b = new G2Point[](numberOfSigners + 1);
        a[0] = negate(signature);
        a[1] = h0;
        a[2] = h1;
        a[3] = h2;
        b[0] = P2();
        b[1] = v0;
        b[2] = v1;
        b[3] = v2;

        return pairing(a, b);
    }

    /// @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[] p1, G2Point[] p2) internal returns (bool) {
        require(p1.length == p2.length);
        uint elements = p1.length;
        uint inputSize = elements * 6;
        uint[] memory input = new uint[](inputSize);

        for (uint i = 0; i < elements; i++)
        {
            input[i * 6 + 0] = p1[i].X;
            input[i * 6 + 1] = p1[i].Y;
            input[i * 6 + 2] = p2[i].X[0];
            input[i * 6 + 3] = p2[i].X[1];
            input[i * 6 + 4] = p2[i].Y[0];
            input[i * 6 + 5] = p2[i].Y[1];
        }

        uint[1] memory out;
        bool success;

        assembly {
            success := call(sub(gas, 2000), 8, 0, add(input, 0x20), mul(inputSize, 0x20), out, 0x20)
        // Use "invalid" to make gas estimation work
            switch success case 0 {invalid}
        }
        require(success);
        return out[0] != 0;
    }

    /// Convenience method for a pairing check for two pairs.
    function pairing2(G1Point a1, G2Point a2, G1Point b1, G2Point b2) internal returns (bool) {
        G1Point[] memory p1 = new G1Point[](2);
        G2Point[] memory p2 = new G2Point[](2);
        p1[0] = a1;
        p1[1] = b1;
        p2[0] = a2;
        p2[1] = b2;
        return pairing(p1, p2);
    }

    function hashToG1(bytes message) internal returns (G1Point) {
        uint256 h = uint256(keccak256(message));
        return mul(P1(), h);
    }

    function modPow(uint256 base, uint256 exponent, uint256 modulus) internal returns (uint256) {
        uint256[6] memory input = [32, 32, 32, base, exponent, modulus];
        uint256[1] memory result;
        assembly {
            if iszero(call(not(0), 0x05, 0, input, 0xc0, result, 0x20)) {
                revert(0, 0)
            }
        }
        return result[0];
    }

    /// @return the negation of p, i.e. p.add(p.negate()) should be zero.
    function negate(G1Point p) internal returns (G1Point) {
        // The prime q in the base field F_q for G1
        uint q = 21888242871839275222246405745257275088696311157297823662689037894645226208583;
        if (p.X == 0 && p.Y == 0)
            return G1Point(0, 0);
        return G1Point(p.X, q - (p.Y % q));
    }

    /// @return the sum of two points of G1
    function add(G1Point p1, G1Point p2) internal returns (G1Point r) {
        uint[4] memory input;
        input[0] = p1.X;
        input[1] = p1.Y;
        input[2] = p2.X;
        input[3] = p2.Y;
        bool success;
        assembly {
            success := call(sub(gas, 2000), 6, 0, input, 0xc0, r, 0x60)
        // Use "invalid" to make gas estimation work
            switch success case 0 {invalid}
        }
        require(success);
    }
    /// @return the product of a point on G1 and a scalar, i.e.
    /// p == p.mul(1) and p.add(p) == p.mul(2) for all points p.
    function mul(G1Point p, uint s) internal returns (G1Point r) {
        uint[3] memory input;
        input[0] = p.X;
        input[1] = p.Y;
        input[2] = s;
        bool success;
        assembly {
            success := call(sub(gas, 2000), 7, 0, input, 0x80, r, 0x60)
        // Use "invalid" to make gas estimation work
            switch success case 0 {invalid}
        }
        require(success);
    }

}

The whole Solidity file is included above to help avoid dead link.

The solcrypto library mentioned in how to implement Cryptographic algorithms in smart contracts may be helpful including the notes in https://ethresear.ch/t/precompiled-snark-pairing-for-bls-signatures/3196/5

To use equivalent of ECPAIRING, you’d then do:

c = pairing(G2, neg(S))
assert a * c == FQ12.one()

To aggregate them:

y = randint(1, p-1) # second secret key
Q = multiply(G2, y) # second public key
T = multiply(H_m, y)  # second signature
d = pairing(add(P, Q), double(H_m))
e = pairing(double(G2, add(S,T))
assert d == e

To verify the aggregates in ECPAIRING style:

d * pairing(double(G2) neg(add(S,T))) == FQ12.one()
  • I've tried to be helpful to get this going but don't know enough on this topic. – eth Sep 24 '18 at 4:55
  • Do you have how much it costs in gas for the verification of the aggregate signatures on the Etherum – Mohamed Oct 18 '18 at 0:03
  • github.com/ethereum/EIPs/blob/master/EIPS/eip-197.md#gas-costs could be a starting point. – eth Oct 22 '18 at 7:30
  • I tried to test the contract above, but when I compile I got two errors in the following function unction modPow(uint256 base, uint256 exponent, uint256 modulus) internal returns (uint256) { uint256[6] memory input = [32, 32, 32, base, exponent, modulus]; uint256[1] memory result; assembly { if iszero(call(not(0), 0x05, 0, input, 0xc0, result, 0x20)) { revert(0, 0) I got errors browser/Pairing.sol:187:13: ParserError: Literal, identifier or instruction expected. if iszero(call(not(0), 0x05, 0, input, 0xc0, result, 0x20) – Mohamed Jun 9 at 22:26
  • @Mohamed If you're now using Solidity 0.5, solidity.readthedocs.io/en/v0.5.9/050-breaking-changes.html might help. Or you can try requesting the gist author for updates: gist.github.com/BjornvdLaan/ca6dd4e3993e1ef392f363ec27fe74c4 – eth Jun 10 at 23:50

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