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Pedersen2 and BitPoints MulFix and MulAny

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This commit is contained in:
Jordi Baylina
2018-11-27 16:03:57 +01:00
parent fcc61f9237
commit 55e9a60c37
40 changed files with 2272 additions and 80 deletions
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64
src/babyjub.js
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@@ -4,6 +4,17 @@ const bigInt = require("snarkjs").bigInt;
exports.addPoint = addPoint;
exports.mulPointEscalar = mulPointEscalar;
exports.inCurve = inCurve;
exports.inSubgroup = inSubgroup;
exports.packPoint = packPoint;
exports.unpackPoint = unpackPoint;
exports.Base8 = [
bigInt("17777552123799933955779906779655732241715742912184938656739573121738514868268"),
bigInt("2626589144620713026669568689430873010625803728049924121243784502389097019475")
];
exports.order = bigInt("21888242871839275222246405745257275088614511777268538073601725287587578984328");
exports.subOrder = exports.order.shr(3);
exports.p = bn128.r;
function addPoint(a,b) {
const q = bn128.r;
@@ -32,26 +43,63 @@ function mulPointEscalar(base, e) {
return res;
}
function isLowGrade(p) {
const r = bigInt("21888242871839275222246405745257275088614511777268538073601725287587578984328").shr(3);
const res= mulPointEscalar(p, r);
function inSubgroup(P) {
if (!inCurve(P)) return false;
const res= mulPointEscalar(P, exports.subOrder);
return (res[0].equals(bigInt(0))) && (res[1].equals(bigInt(1)));
}
function inCurve(p) {
function inCurve(P) {
const F = bn128.Fr;
const a = bigInt("168700");
const d = bigInt("168696");
const x2 = F.square(p[0]);
const y2 = F.square(p[1]);
const x2 = F.square(P[0]);
const y2 = F.square(P[1]);
if (!F.equals(
F.add(F.mul(a, x2), y2),
F.add(F.one, F.mul(F.mul(x2, y2), d)))) return false;
if (!isLowGrade(p)) return false;
return true;
}
function packPoint(P) {
const buff = bigInt.leInt2Buff(P[1], 32);
if (P[0].greater(exports.p.shr(1))) {
buff[31] = buff[31] | 0x80;
}
return buff;
}
function unpackPoint(_buff) {
const F = bn128.Fr;
const buff = Buffer.from(_buff);
let sign = false;
const P = new Array(2);
if (buff[31] & 0x80) {
sign = true;
buff[31] = buff[31] & 0x7F;
}
P[1] = bigInt.leBuff2int(buff);
if (P[1].greaterOrEquals(exports.p)) return null;
const a = bigInt("168700");
const d = bigInt("168696");
const y2 = F.square(P[1]);
let x = F.sqrt(F.div(
F.sub(F.one, y2),
F.sub(a, F.mul(d, y2))));
if (x == null) return null;
if (sign) x = F.neg(x);
P[0] = F.affine(x);
return P;
}