snarkjs/src/setup.js
src/setup.jsRaw
1/*
2 Copyright 2018 0kims association
3
4 This file is part of zksnark javascript library.
5
6 zksnark javascript library is free software: you can redistribute it and/or modify
7 it under the terms of the GNU General Public License as published by
8 the Free Software Foundation, either version 3 of the License, or
9 (at your option) any later version.
10
11 zksnark javascript library is distributed in the hope that it will be useful,
12 but WITHOUT ANY WARRANTY; without even the implied warranty of
13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 GNU General Public License for more details.
15
16 You should have received a copy of the GNU General Public License
17 along with zksnark javascript library. If not, see <https://www.gnu.org/licenses/>.
18*/
19
20const bigInt = require("./bigint.js");
21
22const BN128 = require("./bn128.js");
23const PolField = require("./polfield.js");
24const ZqField = require("./zqfield.js");
25const RatField = require("./ratfield.js");
26
27const bn128 = new BN128();
28const G1 = bn128.G1;
29const G2 = bn128.G2;
30const PolF = new PolField(new ZqField(bn128.r));
31const RatPolF = new PolField(new RatField(new ZqField(bn128.r)));
32const F = new ZqField(bn128.r);
33
34module.exports = function setup(circuit) {
35 const setup = {
36 vk_proof : {
37 nVars: circuit.nVars,
38 nPublic: circuit.nPubInputs + circuit.nOutputs
39 },
40 vk_verifier: {
41 nPublic: circuit.nPubInputs + circuit.nOutputs
42 },
43 toxic: {}
44 };
45
46 calculatePolynomials(setup, circuit);
47 setup.toxic.t = F.random();
48 calculateEncriptedValuesAtT(setup, circuit);
49 calculateHexps(setup, circuit);
50
51 return setup;
52};
53
54function calculatePolynomials(setup, circuit) {
55 // Calculate the points that must cross each polynomial
56
57 setup.toxic.aExtra = [];
58 setup.toxic.bExtra = [];
59 setup.toxic.cExtra = [];
60 const aPoints = [];
61 const bPoints = [];
62 const cPoints = [];
63 for (let s = 0; s<circuit.nVars; s++) {
64 aPoints[s] = [];
65 bPoints[s] = [];
66 cPoints[s] = [];
67 for (let c=0; c<circuit.nConstraints; c++) {
68 aPoints[s].push([[bigInt(c), F.one], [circuit.a(c, s), F.one]]);
69 bPoints[s].push([[bigInt(c), F.one], [circuit.b(c, s), F.one]]);
70 cPoints[s].push([[bigInt(c), F.one], [circuit.c(c, s), F.one]]);
71 }
72 // Add an extra point to avoid constant polinolials.
73 setup.toxic.aExtra[s] = F.random();
74 setup.toxic.bExtra[s] = F.random();
75 setup.toxic.cExtra[s] = F.random();
76 aPoints[s].push([[bigInt(circuit.nConstraints), F.one], [setup.toxic.aExtra[s], F.one]]);
77 bPoints[s].push([[bigInt(circuit.nConstraints), F.one], [setup.toxic.aExtra[s], F.one]]);
78 cPoints[s].push([[bigInt(circuit.nConstraints), F.one], [setup.toxic.aExtra[s], F.one]]);
79 }
80
81 // Calculate the polynomials using Lagrange
82 setup.vk_proof.polsA = [];
83 setup.vk_proof.polsB = [];
84 setup.vk_proof.polsC = [];
85 for (let s=0; s<circuit.nVars; s++) {
86// console.log(`Caclcualte Pol ${s}/${circuit.nVars}`);
87 const pA = RatPolF.lagrange( aPoints[s] );
88 const pB = RatPolF.lagrange( bPoints[s] );
89 const pC = RatPolF.lagrange( cPoints[s] );
90
91 setup.vk_proof.polsA.push( unrat(pA) );
92 setup.vk_proof.polsB.push( unrat(pB) );
93 setup.vk_proof.polsC.push( unrat(pC) );
94
95 }
96
97 // Calculate Z polynomial
98 // Z = 1
99 setup.vk_proof.polZ = [bigInt(1)];
100 for (let c=0; c<circuit.nConstraints; c++) {
101 // Z = Z * (x - p_c)
102 setup.vk_proof.polZ = PolF.mul(
103 setup.vk_proof.polZ,
104 [F.neg(bigInt(c)), bigInt(1)] );
105 }
106}
107
108function calculateEncriptedValuesAtT(setup, circuit) {
109 setup.vk_proof.A = [];
110 setup.vk_proof.B = [];
111 setup.vk_proof.C = [];
112 setup.vk_proof.Ap = [];
113 setup.vk_proof.Bp = [];
114 setup.vk_proof.Cp = [];
115 setup.vk_proof.Kp = [];
116 setup.vk_verifier.A = [];
117
118 setup.toxic.ka = F.random();
119 setup.toxic.kb = F.random();
120 setup.toxic.kc = F.random();
121 setup.toxic.kbeta = F.random();
122 setup.toxic.kgamma = F.random();
123
124 const gb = F.mul(setup.toxic.kbeta, setup.toxic.kgamma);
125
126 setup.vk_verifier.vk_a = G2.affine(G2.mulScalar( G2.g, setup.toxic.ka));
127 setup.vk_verifier.vk_b = G1.affine(G1.mulScalar( G1.g, setup.toxic.kb));
128 setup.vk_verifier.vk_c = G2.affine(G2.mulScalar( G2.g, setup.toxic.kc));
129 setup.vk_verifier.vk_gb_1 = G1.affine(G1.mulScalar( G1.g, gb));
130 setup.vk_verifier.vk_gb_2 = G2.affine(G2.mulScalar( G2.g, gb));
131 setup.vk_verifier.vk_g = G2.affine(G2.mulScalar( G2.g, setup.toxic.kgamma));
132
133 for (let s=0; s<circuit.nVars; s++) {
134
135 // A[i] = G1 * polA(t)
136 const at = F.affine(PolF.eval(setup.vk_proof.polsA[s], setup.toxic.t));
137 const A = G1.affine(G1.mulScalar(G1.g, at));
138
139 setup.vk_proof.A.push(A);
140
141 if (s <= setup.vk_proof.nPublic) {
142 setup.vk_verifier.A.push(A);
143 }
144
145
146 // B1[i] = G1 * polB(t)
147 const bt = F.affine(PolF.eval(setup.vk_proof.polsB[s], setup.toxic.t));
148 const B1 = G1.affine(G1.mulScalar(G1.g, bt));
149
150 // B2[i] = G2 * polB(t)
151 const B2 = G2.affine(G2.mulScalar(G2.g, bt));
152
153 setup.vk_proof.B.push(B2);
154
155 // C[i] = G1 * polC(t)
156 const ct = F.affine(PolF.eval(setup.vk_proof.polsC[s], setup.toxic.t));
157 const C = G1.affine(G1.mulScalar( G1.g, ct));
158 setup.vk_proof.C.push (C);
159
160 // K = G1 * (A+B+C)
161
162 const kt = F.affine(F.add(F.add(at, bt), ct));
163 const K = G1.affine(G1.mulScalar( G1.g, kt));
164
165
166
167 const Ktest = G1.affine(G1.add(G1.add(A, B1), C));
168
169 if (!G1.equals(K, Ktest)) {
170 console.log ("=====FAIL======");
171 }
172
173
174
175 setup.vk_proof.Ap.push(G1.affine(G1.mulScalar(A, setup.toxic.ka)));
176 setup.vk_proof.Bp.push(G1.affine(G1.mulScalar(B1, setup.toxic.kb)));
177 setup.vk_proof.Cp.push(G1.affine(G1.mulScalar(C, setup.toxic.kc)));
178 setup.vk_proof.Kp.push(G1.affine(G1.mulScalar(K, setup.toxic.kbeta)));
179 }
180
181 setup.vk_verifier.vk_z = G2.affine(G2.mulScalar(
182 G2.g,
183 PolF.eval(setup.vk_proof.polZ, setup.toxic.t)));
184}
185
186function calculateHexps(setup, circuit) {
187 let maxA = 0;
188 let maxB = 0;
189 let maxC = 0;
190 for (let s=0; s<circuit.nVars; s++) {
191 maxA = Math.max(maxA, setup.vk_proof.polsA[s].length);
192 maxB = Math.max(maxB, setup.vk_proof.polsB[s].length);
193 maxC = Math.max(maxC, setup.vk_proof.polsC[s].length);
194 }
195
196 let maxFull = Math.max(maxA * maxB - 1, maxC);
197
198 const maxH = maxFull - setup.vk_proof.polZ.length + 1;
199
200 setup.vk_proof.hExps = new Array(maxH);
201 setup.vk_proof.hExps[0] = G1.g;
202 let eT = setup.toxic.t;
203 for (let i=1; i<maxH; i++) {
204 setup.vk_proof.hExps[i] = G1.affine(G1.mulScalar(G1.g, eT));
205 eT = F.mul(eT, setup.toxic.t);
206 }
207}
208
209function unrat(p) {
210 const res = new Array(p.length);
211 for (let i=0; i<p.length; i++) {
212 res[i] = RatPolF.F.toF(p[i]);
213 }
214 return res;
215}
216