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babyjub.js adapted

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Jordi Baylina
2019-12-12 19:46:07 +01:00
parent 30c6cf55b9
commit b4cd3889b6
4 changed files with 92 additions and 60 deletions
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48
src/babyjub.js
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@@ -1,5 +1,6 @@
const bn128 = require("snarkjs").bn128;
const bigInt = require("snarkjs").bigInt;
const bigInt = require("big-integer");
const ZqField = require("fflib").ZqField;
const utils = require("./utils.js");
exports.addPoint = addPoint;
exports.mulPointEscalar = mulPointEscalar;
@@ -16,14 +17,14 @@ exports.Base8 = [
bigInt("16950150798460657717958625567821834550301663161624707787222815936182638968203")
];
exports.order = bigInt("21888242871839275222246405745257275088614511777268538073601725287587578984328");
exports.subOrder = exports.order.shr(3);
exports.p = bn128.r;
exports.subOrder = exports.order.shiftRight(3);
exports.p = bigInt("21888242871839275222246405745257275088548364400416034343698204186575808495617");
exports.A = bigInt("168700");
exports.D = bigInt("168696");
function addPoint(a,b) {
const q = bn128.r;
const F = new ZqField(exports.p);
const res = [];
@@ -31,8 +32,25 @@ function addPoint(a,b) {
res[0] = bigInt((a[0]*b[1] + b[0]*a[1]) * bigInt(bigInt("1") + d*a[0]*b[0]*a[1]*b[1]).inverse(q)).affine(q);
res[1] = bigInt((a[1]*b[1] - cta*a[0]*b[0]) * bigInt(bigInt("1") - d*a[0]*b[0]*a[1]*b[1]).inverse(q)).affine(q);
*/
res[0] = bigInt((bigInt(a[0]).mul(b[1]).add(bigInt(b[0]).mul(a[1]))).mul(bigInt(bigInt("1").add(exports.D.mul(a[0]).mul(b[0]).mul(a[1]).mul(b[1]))).inverse(q))).affine(q);
res[1] = bigInt((bigInt(a[1]).mul(b[1]).sub(exports.A.mul(a[0]).mul(b[0]))).mul(bigInt(bigInt("1").sub(exports.D.mul(a[0]).mul(b[0]).mul(a[1]).mul(b[1]))).inverse(q))).affine(q);
const beta = F.mul(a[0],b[1]);
const gamma = F.mul(a[1],b[0]);
const delta = F.mul(
F.sub(a[1], F.mul(exports.A, a[0])),
F.add(b[0], b[1])
);
const tau = F.mul(beta, gamma);
const dtau = F.mul(exports.D, tau);
res[0] = F.div(
F.add(beta, gamma),
F.add(bigInt.one, dtau)
);
res[1] = F.div(
F.add(delta, F.sub(F.mul(exports.A,beta), gamma)),
F.sub(bigInt.one, dtau)
);
return res;
}
@@ -47,7 +65,7 @@ function mulPointEscalar(base, e) {
res = addPoint(res, exp);
}
exp = addPoint(exp, exp);
rem = rem.shr(1);
rem = rem.shiftRight(1);
}
return res;
@@ -60,12 +78,12 @@ function inSubgroup(P) {
}
function inCurve(P) {
const F = bn128.Fr;
const F = new ZqField(exports.p);
const x2 = F.square(P[0]);
const y2 = F.square(P[1]);
if (!F.equals(
if (!F.eq(
F.add(F.mul(exports.A, x2), y2),
F.add(F.one, F.mul(F.mul(x2, y2), exports.D)))) return false;
@@ -73,15 +91,15 @@ function inCurve(P) {
}
function packPoint(P) {
const buff = bigInt.leInt2Buff(P[1], 32);
if (P[0].greater(exports.p.shr(1))) {
const buff = utils.leInt2Buff(P[1], 32);
if (P[0].greater(exports.p.shiftRight(1))) {
buff[31] = buff[31] | 0x80;
}
return buff;
}
function unpackPoint(_buff) {
const F = bn128.Fr;
const F = new ZqField(exports.p);
const buff = Buffer.from(_buff);
let sign = false;
@@ -90,7 +108,7 @@ function unpackPoint(_buff) {
sign = true;
buff[31] = buff[31] & 0x7F;
}
P[1] = bigInt.leBuff2int(buff);
P[1] = utils.leBuff2int(buff);
if (P[1].greaterOrEquals(exports.p)) return null;
const y2 = F.square(P[1]);
@@ -103,7 +121,7 @@ function unpackPoint(_buff) {
if (sign) x = F.neg(x);
P[0] = F.affine(x);
P[0] = x;
return P;
}