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 calculatePolinomials(setup, circuit);
47 setup.toxic.t = F.random();
48 calculateEncriptedValuesAtT(setup, circuit);
49 calculateHexps(setup, circuit);
50
51 return setup;
52};
53
54function calculatePolinomials(setup, circuit) {
55 // Calculate the points that must cross each polinomial
56 const aPoints = [];
57 const bPoints = [];
58 const cPoints = [];
59 for (let s = 0; s<circuit.nSignals; s++) {
60 aPoints[s] = [];
61 bPoints[s] = [];
62 cPoints[s] = [];
63 for (let c=0; c<circuit.nConstrains; c++) {
64 aPoints[s].push([[bigInt(c), F.one], [circuit.a(c, s), F.one]]);
65 bPoints[s].push([[bigInt(c), F.one], [circuit.b(c, s), F.one]]);
66 cPoints[s].push([[bigInt(c), F.one], [circuit.c(c, s), F.one]]);
67 }
68 }
69
70 // Calculate the polinomials using Lagrange
71 setup.vk_proof.polsA = [];
72 setup.vk_proof.polsB = [];
73 setup.vk_proof.polsC = [];
74 for (let s=0; s<circuit.nSignals; s++) {
75// console.log(`Caclcualte Pol ${s}/${circuit.nSignals}`);
76 const pA = RatPolF.lagrange( aPoints[s] );
77 const pB = RatPolF.lagrange( bPoints[s] );
78 const pC = RatPolF.lagrange( cPoints[s] );
79
80 setup.vk_proof.polsA.push( unrat(pA) );
81 setup.vk_proof.polsB.push( unrat(pB) );
82 setup.vk_proof.polsC.push( unrat(pC) );
83
84 }
85
86 // Calculate Z polinomial
87 // Z = 1
88 setup.vk_proof.polZ = [bigInt(1)];
89 for (let c=0; c<circuit.nConstrains; c++) {
90 // Z = Z * (x - p_c)
91 setup.vk_proof.polZ = PolF.mul(
92 setup.vk_proof.polZ,
93 [F.neg(bigInt(c)), bigInt(1)] );
94 }
95}
96
97function calculateEncriptedValuesAtT(setup, circuit) {
98 setup.vk_proof.A = [];
99 setup.vk_proof.B = [];
100 setup.vk_proof.C = [];
101 setup.vk_proof.Ap = [];
102 setup.vk_proof.Bp = [];
103 setup.vk_proof.Cp = [];
104 setup.vk_proof.Kp = [];
105 setup.vk_verifier.A = [];
106
107 setup.toxic.ka = F.random();
108 setup.toxic.kb = F.random();
109 setup.toxic.kc = F.random();
110 setup.toxic.kbeta = F.random();
111 setup.toxic.kgamma = F.random();
112
113 const gb = F.mul(setup.toxic.kbeta, setup.toxic.kgamma);
114
115 setup.vk_verifier.vk_a = G2.affine(G2.mulScalar( G2.g, setup.toxic.ka));
116 setup.vk_verifier.vk_b = G1.affine(G1.mulScalar( G1.g, setup.toxic.kb));
117 setup.vk_verifier.vk_c = G2.affine(G2.mulScalar( G2.g, setup.toxic.kc));
118 setup.vk_verifier.vk_gb_1 = G1.affine(G1.mulScalar( G1.g, gb));
119 setup.vk_verifier.vk_gb_2 = G2.affine(G2.mulScalar( G2.g, gb));
120 setup.vk_verifier.vk_g = G2.affine(G2.mulScalar( G2.g, setup.toxic.kgamma));
121
122 for (let s=0; s<circuit.nSignals; s++) {
123
124 // A[i] = G1 * polA(t)
125 const at = F.affine(PolF.eval(setup.vk_proof.polsA[s], setup.toxic.t));
126 const A = G1.affine(G1.mulScalar(G1.g, at));
127
128 setup.vk_proof.A.push(A);
129
130 if (s <= setup.vk_proof.nPublic) {
131 setup.vk_verifier.A.push(A);
132 }
133
134
135 // B1[i] = G1 * polB(t)
136 const bt = F.affine(PolF.eval(setup.vk_proof.polsB[s], setup.toxic.t));
137 const B1 = G1.affine(G1.mulScalar(G1.g, bt));
138
139 // B2[i] = G2 * polB(t)
140 const B2 = G2.affine(G2.mulScalar(G2.g, bt));
141
142 setup.vk_proof.B.push(B2);
143
144 // C[i] = G1 * polC(t)
145 const ct = F.affine(PolF.eval(setup.vk_proof.polsC[s], setup.toxic.t));
146 const C = G1.affine(G1.mulScalar( G1.g, ct));
147 setup.vk_proof.C.push (C);
148
149 // K = G1 * (A+B+C)
150
151 const kt = F.affine(F.add(F.add(at, bt), ct));
152 const K = G1.affine(G1.mulScalar( G1.g, kt));
153
154
155
156 const Ktest = G1.affine(G1.add(G1.add(A, B1), C));
157
158 if (!G1.equals(K, Ktest)) {
159 console.log ("=====FAIL======");
160 }
161
162
163
164 setup.vk_proof.Ap.push(G1.affine(G1.mulScalar(A, setup.toxic.ka)));
165 setup.vk_proof.Bp.push(G1.affine(G1.mulScalar(B1, setup.toxic.kb)));
166 setup.vk_proof.Cp.push(G1.affine(G1.mulScalar(C, setup.toxic.kc)));
167 setup.vk_proof.Kp.push(G1.affine(G1.mulScalar(K, setup.toxic.kbeta)));
168 }
169
170 setup.vk_verifier.vk_z = G2.affine(G2.mulScalar(
171 G2.g,
172 PolF.eval(setup.vk_proof.polZ, setup.toxic.t)));
173}
174
175function calculateHexps(setup, circuit) {
176 let maxA = 0;
177 let maxB = 0;
178 let maxC = 0;
179 for (let s=0; s<circuit.nSignals; s++) {
180 maxA = Math.max(maxA, setup.vk_proof.polsA[s].length);
181 maxB = Math.max(maxB, setup.vk_proof.polsB[s].length);
182 maxC = Math.max(maxC, setup.vk_proof.polsC[s].length);
183 }
184
185 let maxFull = Math.max(maxA * maxB - 1, maxC);
186
187 const maxH = maxFull - setup.vk_proof.polZ.length + 1;
188
189 setup.vk_proof.hExps = new Array(maxH);
190 setup.vk_proof.hExps[0] = G1.g;
191 let eT = setup.toxic.t;
192 for (let i=1; i<maxH; i++) {
193 setup.vk_proof.hExps[i] = G1.affine(G1.mulScalar(G1.g, eT));
194 eT = F.mul(eT, setup.toxic.t);
195 }
196}
197
198function unrat(p) {
199 const res = new Array(p.length);
200 for (let i=0; i<p.length; i++) {
201 res[i] = RatPolF.F.toF(p[i]);
202 }
203 return res;
204}
205