zkSNARKs test code

snarktest.solidity

// This file is MIT Licensed.
//
// Copyright 2017 Christian Reitwiessner
// Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:
// The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

pragma solidity ^0.4.14;

library Pairing {
	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]
		);
	}
	/// @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);
	}
	/// @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 pairingProd2(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);
	}
	/// Convenience method for a pairing check for three pairs.
	function pairingProd3(
			G1Point a1, G2Point a2,
			G1Point b1, G2Point b2,
			G1Point c1, G2Point c2
	) internal returns (bool) {
		G1Point[] memory p1 = new G1Point[](3);
		G2Point[] memory p2 = new G2Point[](3);
		p1[0] = a1;
		p1[1] = b1;
		p1[2] = c1;
		p2[0] = a2;
		p2[1] = b2;
		p2[2] = c2;
		return pairing(p1, p2);
	}
	/// Convenience method for a pairing check for four pairs.
	function pairingProd4(
			G1Point a1, G2Point a2,
			G1Point b1, G2Point b2,
			G1Point c1, G2Point c2,
			G1Point d1, G2Point d2
	) internal returns (bool) {
		G1Point[] memory p1 = new G1Point[](4);
		G2Point[] memory p2 = new G2Point[](4);
		p1[0] = a1;
		p1[1] = b1;
		p1[2] = c1;
		p1[3] = d1;
		p2[0] = a2;
		p2[1] = b2;
		p2[2] = c2;
		p2[3] = d2;
		return pairing(p1, p2);
	}
}
contract Test {
	using Pairing for *;
	struct VerifyingKey {
		Pairing.G2Point A;
		Pairing.G1Point B;
		Pairing.G2Point C;
		Pairing.G2Point gamma;
		Pairing.G1Point gammaBeta1;
		Pairing.G2Point gammaBeta2;
		Pairing.G2Point Z;
		Pairing.G1Point[] IC;
	}
	struct Proof {
		Pairing.G1Point A;
		Pairing.G1Point A_p;
		Pairing.G2Point B;
		Pairing.G1Point B_p;
		Pairing.G1Point C;
		Pairing.G1Point C_p;
		Pairing.G1Point K;
		Pairing.G1Point H;
	}
	function f() returns (bool) {
		Pairing.G1Point memory p1;
		Pairing.G1Point memory p2;
		p1.X = 1; p1.Y = 2;
		p2.X = 1; p2.Y = 2;
		var explict_sum = Pairing.add(p1, p2);
		var scalar_prod = Pairing.mul(p1, 2);
		return (explict_sum.X == scalar_prod.X &&
				explict_sum.Y == scalar_prod.Y);
	}
	function g() returns (bool) {
		Pairing.G1Point memory x = Pairing.add(Pairing.P1(), Pairing.negate(Pairing.P1()));
		// should be zero
		return (x.X == 0 && x.Y == 0);
	}
	function testMul() returns (bool) {
		Pairing.G1Point memory p;
		// @TODO The points here are reported to be not well-formed
		p.X = 14125296762497065001182820090155008161146766663259912659363835465243039841726;
		p.Y = 16229134936871442251132173501211935676986397196799085184804749187146857848057;
		p = Pairing.mul(p, 13986731495506593864492662381614386532349950841221768152838255933892789078521);
		return
			p.X == 18256332256630856740336504687838346961237861778318632856900758565550522381207 &&
			p.Y == 6976682127058094634733239494758371323697222088503263230319702770853579280803;
	}
	function pair() returns (bool) {
		Pairing.G2Point memory fiveTimesP2 = Pairing.G2Point(
			[4540444681147253467785307942530223364530218361853237193970751657229138047649, 20954117799226682825035885491234530437475518021362091509513177301640194298072],
			[11631839690097995216017572651900167465857396346217730511548857041925508482915, 21508930868448350162258892668132814424284302804699005394342512102884055673846]
		);
		// The prime p in the base field F_p for G1
		uint p = 21888242871839275222246405745257275088696311157297823662689037894645226208583;
		Pairing.G1Point[] memory g1points = new Pairing.G1Point[](2);
		Pairing.G2Point[] memory g2points = new Pairing.G2Point[](2);
// 			// check e(5 P1, P2)e(-P1, 5 P2) == 1
		g1points[0] = Pairing.P1().mul(5);
		g1points[1] = Pairing.P1();
		g1points[1].Y = p - g1points[1].Y;
		g2points[0] = Pairing.P2();
		g2points[1] = fiveTimesP2;
		if (!Pairing.pairing(g1points, g2points))
			return false;
		// check e(P1, P2)e(-P1, P2) == 0
		g1points[0] = Pairing.P1();
		g1points[1] = Pairing.P1().negate();
		g2points[0] = Pairing.P2();
		g2points[1] = Pairing.P2();
		if (!Pairing.pairing(g1points, g2points))
			return false;
		return true;
	}
	function verifyingKey() internal returns (VerifyingKey vk) {
		vk.A = Pairing.G2Point([0x209dd15ebff5d46c4bd888e51a93cf99a7329636c63514396b4a452003a35bf7, 0x04bf11ca01483bfa8b34b43561848d28905960114c8ac04049af4b6315a41678], [0x2bb8324af6cfc93537a2ad1a445cfd0ca2a71acd7ac41fadbf933c2a51be344d, 0x120a2a4cf30c1bf9845f20c6fe39e07ea2cce61f0c9bb048165fe5e4de877550]);
		vk.B = Pairing.G1Point(0x2eca0c7238bf16e83e7a1e6c5d49540685ff51380f309842a98561558019fc02, 0x03d3260361bb8451de5ff5ecd17f010ff22f5c31cdf184e9020b06fa5997db84);
		vk.C = Pairing.G2Point([0x2e89718ad33c8bed92e210e81d1853435399a271913a6520736a4729cf0d51eb, 0x01a9e2ffa2e92599b68e44de5bcf354fa2642bd4f26b259daa6f7ce3ed57aeb3], [0x14a9a87b789a58af499b314e13c3d65bede56c07ea2d418d6874857b70763713, 0x178fb49a2d6cd347dc58973ff49613a20757d0fcc22079f9abd10c3baee24590]);
		vk.gamma = Pairing.G2Point([0x25f83c8b6ab9de74e7da488ef02645c5a16a6652c3c71a15dc37fe3a5dcb7cb1, 0x22acdedd6308e3bb230d226d16a105295f523a8a02bfc5e8bd2da135ac4c245d], [0x065bbad92e7c4e31bf3757f1fe7362a63fbfee50e7dc68da116e67d600d9bf68, 0x06d302580dc0661002994e7cd3a7f224e7ddc27802777486bf80f40e4ca3cfdb]);
		vk.gammaBeta1 = Pairing.G1Point(0x15794ab061441e51d01e94640b7e3084a07e02c78cf3103c542bc5b298669f21, 0x14db745c6780e9df549864cec19c2daf4531f6ec0c89cc1c7436cc4d8d300c6d);
		vk.gammaBeta2 = Pairing.G2Point([0x1f39e4e4afc4bc74790a4a028aff2c3d2538731fb755edefd8cb48d6ea589b5e, 0x283f150794b6736f670d6a1033f9b46c6f5204f50813eb85c8dc4b59db1c5d39], [0x140d97ee4d2b36d99bc49974d18ecca3e7ad51011956051b464d9e27d46cc25e, 0x0764bb98575bd466d32db7b15f582b2d5c452b36aa394b789366e5e3ca5aabd4]);
		vk.Z = Pairing.G2Point([0x217cee0a9ad79a4493b5253e2e4e3a39fc2df38419f230d341f60cb064a0ac29, 0x0a3d76f140db8418ba512272381446eb73958670f00cf46f1d9e64cba057b53c], [0x26f64a8ec70387a13e41430ed3ee4a7db2059cc5fc13c067194bcc0cb49a9855, 0x2fd72bd9edb657346127da132e5b82ab908f5816c826acb499e22f2412d1a2d7]);
		vk.IC = new Pairing.G1Point[](10);
		vk.IC[0] = Pairing.G1Point(0x0aee46a7ea6e80a3675026dfa84019deee2a2dedb1bbe11d7fe124cb3efb4b5a, 0x044747b6e9176e13ede3a4dfd0d33ccca6321b9acd23bf3683a60adc0366ebaf);
		vk.IC[1] = Pairing.G1Point(0x1e39e9f0f91fa7ff8047ffd90de08785777fe61c0e3434e728fce4cf35047ddc, 0x2e0b64d75ebfa86d7f8f8e08abbe2e7ae6e0a1c0b34d028f19fa56e9450527cb);
		vk.IC[2] = Pairing.G1Point(0x1c36e713d4d54e3a9644dffca1fc524be4868f66572516025a61ca542539d43f, 0x042dcc4525b82dfb242b09cb21909d5c22643dcdbe98c4d082cc2877e96b24db);
		vk.IC[3] = Pairing.G1Point(0x17d5d09b4146424bff7e6fb01487c477bbfcd0cdbbc92d5d6457aae0b6717cc5, 0x02b5636903efbf46db9235bbe74045d21c138897fda32e079040db1a16c1a7a1);
		vk.IC[4] = Pairing.G1Point(0x0f103f14a584d4203c27c26155b2c955f8dfa816980b24ba824e1972d6486a5d, 0x0c4165133b9f5be17c804203af781bcf168da7386620479f9b885ecbcd27b17b);
		vk.IC[5] = Pairing.G1Point(0x232063b584fb76c8d07995bee3a38fa7565405f3549c6a918ddaa90ab971e7f8, 0x2ac9b135a81d96425c92d02296322ad56ffb16299633233e4880f95aafa7fda7);
		vk.IC[6] = Pairing.G1Point(0x09b54f111d3b2d1b2fe1ae9669b3db3d7bf93b70f00647e65c849275de6dc7fe, 0x18b2e77c63a3e400d6d1f1fbc6e1a1167bbca603d34d03edea231eb0ab7b14b4);
		vk.IC[7] = Pairing.G1Point(0x0c54b42137b67cc268cbb53ac62b00ecead23984092b494a88befe58445a244a, 0x18e3723d37fae9262d58b548a0575f59d9c3266db7afb4d5739555837f6b8b3e);
		vk.IC[8] = Pairing.G1Point(0x0a6de0e2240aa253f46ce0da883b61976e3588146e01c9d8976548c145fe6e4a, 0x04fbaa3a4aed4bb77f30ebb07a3ec1c7d77a7f2edd75636babfeff97b1ea686e);
		vk.IC[9] = Pairing.G1Point(0x111e2e2a5f8828f80ddad08f9f74db56dac1cc16c1cb278036f79a84cf7a116f, 0x1d7d62e192b219b9808faa906c5ced871788f6339e8d91b83ac1343e20a16b30);
	}
	function verify(uint[] input, Proof proof) internal returns (uint) {
		VerifyingKey memory vk = verifyingKey();
		require(input.length + 1 == vk.IC.length);
		// Compute the linear combination vk_x
		Pairing.G1Point memory vk_x = Pairing.G1Point(0, 0);
		for (uint i = 0; i < input.length; i++)
			vk_x = Pairing.add(vk_x, Pairing.mul(vk.IC[i + 1], input[i]));
		vk_x = Pairing.add(vk_x, vk.IC[0]);
		if (!Pairing.pairingProd2(proof.A, vk.A, Pairing.negate(proof.A_p), Pairing.P2())) return 1;
		if (!Pairing.pairingProd2(vk.B, proof.B, Pairing.negate(proof.B_p), Pairing.P2())) return 2;
		if (!Pairing.pairingProd2(proof.C, vk.C, Pairing.negate(proof.C_p), Pairing.P2())) return 3;
		if (!Pairing.pairingProd3(
			proof.K, vk.gamma,
			Pairing.negate(Pairing.add(vk_x, Pairing.add(proof.A, proof.C))), vk.gammaBeta2,
			Pairing.negate(vk.gammaBeta1), proof.B
		)) return 4;
		if (!Pairing.pairingProd3(
				Pairing.add(vk_x, proof.A), proof.B,
				Pairing.negate(proof.H), vk.Z,
				Pairing.negate(proof.C), Pairing.P2()
		)) return 5;
		return 0;
	}
	event Verified(string);
	function verifyTx() returns (bool r) {
		uint[] memory input = new uint[](9);
		Proof memory proof;
		proof.A = Pairing.G1Point(12873740738727497448187997291915224677121726020054032516825496230827252793177, 21804419174137094775122804775419507726154084057848719988004616848382402162497);
		proof.A_p = Pairing.G1Point(7742452358972543465462254569134860944739929848367563713587808717088650354556, 7324522103398787664095385319014038380128814213034709026832529060148225837366);
		proof.B = Pairing.G2Point(
			[8176651290984905087450403379100573157708110416512446269839297438960217797614, 15588556568726919713003060429893850972163943674590384915350025440408631945055],
			[15347511022514187557142999444367533883366476794364262773195059233657571533367, 4265071979090628150845437155927259896060451682253086069461962693761322642015]);
		proof.B_p = Pairing.G1Point(2979746655438963305714517285593753729335852012083057917022078236006592638393, 6470627481646078059765266161088786576504622012540639992486470834383274712950);
		proof.C = Pairing.G1Point(6851077925310461602867742977619883934042581405263014789956638244065803308498, 10336382210592135525880811046708757754106524561907815205241508542912494488506);
		proof.C_p = Pairing.G1Point(12491625890066296859584468664467427202390981822868257437245835716136010795448, 13818492518017455361318553880921248537817650587494176379915981090396574171686);
		proof.H = Pairing.G1Point(12091046215835229523641173286701717671667447745509192321596954139357866668225, 14446807589950902476683545679847436767890904443411534435294953056557941441758);
		proof.K = Pairing.G1Point(21341087976609916409401737322664290631992568431163400450267978471171152600502, 2942165230690572858696920423896381470344658299915828986338281196715687693170);
		input[0] = 13986731495506593864492662381614386532349950841221768152838255933892789078521;
		input[1] = 622860516154313070522697309645122400675542217310916019527100517240519630053;
		input[2] = 11094488463398718754251685950409355128550342438297986977413505294941943071569;
		input[3] = 6627643779954497813586310325594578844876646808666478625705401786271515864467;
		input[4] = 2957286918163151606545409668133310005545945782087581890025685458369200827463;
		input[5] = 1384290496819542862903939282897996566903332587607290986044945365745128311081;
		input[6] = 5613571677741714971687805233468747950848449704454346829971683826953541367271;
		input[7] = 9643208548031422463313148630985736896287522941726746581856185889848792022807;
		input[8] = 18066496933330839731877828156604;
		if (verify(input, proof) == 0) {
		    Verified("Transaction successfully verified.");
		    return true;
		} else {
		    return false;
		}
	}
}

Can you describe how to use it ? thx

Any explanation on how to use this?

yeah this looks awesome, but have no idea where to even start.

@georgek146 https://medium.com/@VitalikButerin/zk-snarks-under-the-hood-b33151a013f6

So awesome Thank you so much

@vjuge @saitam1 @georgek146 @jusdev89 we are working on tools to make this easier: https://www.youtube.com/watch?v=_QyXreu64kQ&index=12&list=PLaM7G4Llrb7wPiT2G75tj2JQr8qg6P5hi
They will probably be released at devcon.

@chriseth - is verifyTx using a real world zcash tx?
EDIT: i saw on reddit that it is. was hoping to get the tx hash but i suppose you dont have it anymore.

What is verified here is the zkSNARK part of some real transaction on the real zCash network. I pulled the data out of the chain some time around January, I think. I have no idea who created the transaction or how much money is sent inside it, but now the Ethereum network knows it is correct :-)

@chriseth - curious why vk.B and proof.B are swapped here (maybe the order doesnt matter)

		if (!Pairing.pairingProd2(proof.A, vk.A, Pairing.negate(proof.A_p), Pairing.P2())) return 1;
		if (!Pairing.pairingProd2(vk.B, proof.B, Pairing.negate(proof.B_p), Pairing.P2())) return 2;
		if (!Pairing.pairingProd2(proof.C, vk.C, Pairing.negate(proof.C_p), Pairing.P2())) return 3;

@chriseth : saw the presentation at devcon (mainstage one - remotely), happy to get the github repo, and will check it out :)

@chriseth
I have a doubt about this line: success := call(sub(gas, 2000), 8, 0, add(input, 0x20), mul(inputSize, 0x20), out, 0x20)
what does the address param (8) means? As I see in Solidity documentation, this opcode has the following description: "call contract at address a with input mem[in..(in+insize)) providing g gas and v wei and output area mem[out..(out+outsize)) returning 0 on error (eg. out of gas) and 1 on success"

One more doubt. Could you explain me (cause I'm quite noob) why, in pairing function, position 0 of out param always is 0? It makes that verifyTx function always returns false.

Thank you!

Hi again @chriseth,
I deployed the contract and tried verifyTx() function but transaction always fails. Do you know why?
Thank you!

hi @chriseth
I have the same question with marmengol.
What does the addree param(8) means? thanks

@marmengol I was able to test the verifyTx() function on a private network using this exact code. Make sure your geth client is greater than 1.7.0 and that you are using Byzantium (for a private network: include "ByzantiumBlock": 0 in your genesis.json)

@jackieWhn if I'm not mistaken the addr 8 refers to the precompiled bn256Pairing contract

@matthieu-merlyn, i test the verifyTx() function on a private network, return false. f() function, return true. why?

could you show the ZoKrates code to generate this verification code?

@marmengol @jackieWhn @matthieu-merlyn
Indeed, it is the 8th precompiled Ethereum contract, as explained here.
The specification of this particular contract is in here.

Precompiled contracts are not written in EVM bytecode, they are directly implemented by the client. The Geth implementation for the precompiled contracts is here:

var PrecompiledContractsByzantium = map[common.Address]PrecompiledContract{
	common.BytesToAddress([]byte{1}): &ecrecover{},
	common.BytesToAddress([]byte{2}): &sha256hash{},
	common.BytesToAddress([]byte{3}): &ripemd160hash{},
	common.BytesToAddress([]byte{4}): &dataCopy{},
	common.BytesToAddress([]byte{5}): &bigModExp{},
	common.BytesToAddress([]byte{6}): &bn256Add{},
	common.BytesToAddress([]byte{7}): &bn256ScalarMul{},
	common.BytesToAddress([]byte{8}): &bn256Pairing{},
}

Contract 8 is actually implemented by the last function in the file: it extracts two sets of points and computes the product of their pairings. The actual work is done by function bn256.PairingCheck(cs, ts), which is implemented here.