@noble/curves
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Audited & minimal JS implementation of elliptic curve cryptography
714 lines • 36.5 kB
JavaScript
/**
* bls12-381 is pairing-friendly Barreto-Lynn-Scott elliptic curve construction allowing to:
* * Construct zk-SNARKs at the ~120-bit security
* * Efficiently verify N aggregate signatures with 1 pairing and N ec additions:
* the Boneh-Lynn-Shacham signature scheme is orders of magnitude more efficient than Schnorr
*
* ### Summary
* 1. BLS Relies on Bilinear Pairing (expensive)
* 2. Private Keys: 32 bytes
* 3. Public Keys: 48 bytes: 381 bit affine x coordinate, encoded into 48 big-endian bytes.
* 4. Signatures: 96 bytes: two 381 bit integers (affine x coordinate), encoded into two 48 big-endian byte arrays.
* - The signature is a point on the G2 subgroup, which is defined over a finite field
* with elements twice as big as the G1 curve (G2 is over Fp2 rather than Fp. Fp2 is analogous to the
* complex numbers).
* - We also support reversed 96-byte pubkeys & 48-byte short signatures.
* 5. The 12 stands for the Embedding degree.
*
* ### Formulas
* - `P = pk x G` - public keys
* - `S = pk x H(m)` - signing
* - `e(P, H(m)) == e(G, S)` - verification using pairings
* - `e(G, S) = e(G, SUM(n)(Si)) = MUL(n)(e(G, Si))` - signature aggregation
*
* ### Compatibility and notes
* 1. It is compatible with Algorand, Chia, Dfinity, Ethereum, Filecoin, ZEC.
* Filecoin uses little endian byte arrays for private keys - make sure to reverse byte order.
* 2. Some projects use G2 for public keys and G1 for signatures. It's called "short signature".
* 3. Curve security level is about 120 bits as per [Barbulescu-Duquesne 2017](https://hal.science/hal-01534101/file/main.pdf)
* 4. Compatible with specs:
* [cfrg-pairing-friendly-curves-11](https://tools.ietf.org/html/draft-irtf-cfrg-pairing-friendly-curves-11),
* [cfrg-bls-signature-05](https://datatracker.ietf.org/doc/html/draft-irtf-cfrg-bls-signature-05),
* [RFC 9380](https://www.rfc-editor.org/rfc/rfc9380).
*
* ### Params
* To verify curve parameters, see
* [pairing-friendly-curves spec](https://datatracker.ietf.org/doc/html/draft-irtf-cfrg-pairing-friendly-curves-11).
* Basic math is done over finite fields over p.
* More complicated math is done over polynominal extension fields.
* To simplify calculations in Fp12, we construct extension tower:
*
* Embedding degree (k): 12
* Seed (X): -15132376222941642752
* Fr: (x⁴-x²+1)
* Fp: ((x-1)² ⋅ r(x)/3+x)
* (E/Fp): Y²=X³+4
* (Eₜ/Fp²): Y² = X³+4(u+1) (M-type twist)
* Ate loop size: X
*
* ### Towers
* - Fp₁₂ = Fp₆² => Fp₂³
* - Fp(u) / (u² - β) where β = -1
* - Fp₂(v) / (v³ - ξ) where ξ = u + 1
* - Fp₆(w) / (w² - γ) where γ = v
* - Fp²[u] = Fp/u²+1
* - Fp⁶[v] = Fp²/v³-1-u
* - Fp¹²[w] = Fp⁶/w²-v
*
* @todo construct bls & bn fp/fr from seed.
* @module
*/
/*! noble-curves - MIT License (c) 2022 Paul Miller (paulmillr.com) */
import { sha256 } from '@noble/hashes/sha256';
import { randomBytes } from '@noble/hashes/utils';
import { bls } from './abstract/bls.js';
import * as mod from './abstract/modular.js';
import { bitGet, bitLen, bytesToHex, bytesToNumberBE, concatBytes as concatB, ensureBytes, numberToBytesBE, } from './abstract/utils.js';
// Types
import { isogenyMap } from './abstract/hash-to-curve.js';
import { psiFrobenius, tower12 } from './abstract/tower.js';
import { mapToCurveSimpleSWU, } from './abstract/weierstrass.js';
// Be friendly to bad ECMAScript parsers by not using bigint literals
// prettier-ignore
const _0n = BigInt(0), _1n = BigInt(1), _2n = BigInt(2), _3n = BigInt(3), _4n = BigInt(4);
// The BLS parameter x (seed) for BLS12-381. NOTE: it is negative!
const BLS_X = BigInt('0xd201000000010000');
const BLS_X_LEN = bitLen(BLS_X);
// CURVE FIELDS
const { Fp, Fp2, Fp6, Fp4Square, Fp12 } = tower12({
// Order of Fp
ORDER: BigInt('0x1a0111ea397fe69a4b1ba7b6434bacd764774b84f38512bf6730d2a0f6b0f6241eabfffeb153ffffb9feffffffffaaab'),
// Finite extension field over irreducible polynominal.
// Fp(u) / (u² - β) where β = -1
FP2_NONRESIDUE: [_1n, _1n],
Fp2mulByB: ({ c0, c1 }) => {
const t0 = Fp.mul(c0, _4n); // 4 * c0
const t1 = Fp.mul(c1, _4n); // 4 * c1
// (T0-T1) + (T0+T1)*i
return { c0: Fp.sub(t0, t1), c1: Fp.add(t0, t1) };
},
// Fp12
// A cyclotomic group is a subgroup of Fp^n defined by
// GΦₙ(p) = {α ∈ Fpⁿ : α^Φₙ(p) = 1}
// The result of any pairing is in a cyclotomic subgroup
// https://eprint.iacr.org/2009/565.pdf
Fp12cyclotomicSquare: ({ c0, c1 }) => {
const { c0: c0c0, c1: c0c1, c2: c0c2 } = c0;
const { c0: c1c0, c1: c1c1, c2: c1c2 } = c1;
const { first: t3, second: t4 } = Fp4Square(c0c0, c1c1);
const { first: t5, second: t6 } = Fp4Square(c1c0, c0c2);
const { first: t7, second: t8 } = Fp4Square(c0c1, c1c2);
const t9 = Fp2.mulByNonresidue(t8); // T8 * (u + 1)
return {
c0: Fp6.create({
c0: Fp2.add(Fp2.mul(Fp2.sub(t3, c0c0), _2n), t3), // 2 * (T3 - c0c0) + T3
c1: Fp2.add(Fp2.mul(Fp2.sub(t5, c0c1), _2n), t5), // 2 * (T5 - c0c1) + T5
c2: Fp2.add(Fp2.mul(Fp2.sub(t7, c0c2), _2n), t7),
}), // 2 * (T7 - c0c2) + T7
c1: Fp6.create({
c0: Fp2.add(Fp2.mul(Fp2.add(t9, c1c0), _2n), t9), // 2 * (T9 + c1c0) + T9
c1: Fp2.add(Fp2.mul(Fp2.add(t4, c1c1), _2n), t4), // 2 * (T4 + c1c1) + T4
c2: Fp2.add(Fp2.mul(Fp2.add(t6, c1c2), _2n), t6),
}),
}; // 2 * (T6 + c1c2) + T6
},
Fp12cyclotomicExp(num, n) {
let z = Fp12.ONE;
for (let i = BLS_X_LEN - 1; i >= 0; i--) {
z = Fp12._cyclotomicSquare(z);
if (bitGet(n, i))
z = Fp12.mul(z, num);
}
return z;
},
// https://eprint.iacr.org/2010/354.pdf
// https://eprint.iacr.org/2009/565.pdf
Fp12finalExponentiate: (num) => {
const x = BLS_X;
// this^(q⁶) / this
const t0 = Fp12.div(Fp12.frobeniusMap(num, 6), num);
// t0^(q²) * t0
const t1 = Fp12.mul(Fp12.frobeniusMap(t0, 2), t0);
const t2 = Fp12.conjugate(Fp12._cyclotomicExp(t1, x));
const t3 = Fp12.mul(Fp12.conjugate(Fp12._cyclotomicSquare(t1)), t2);
const t4 = Fp12.conjugate(Fp12._cyclotomicExp(t3, x));
const t5 = Fp12.conjugate(Fp12._cyclotomicExp(t4, x));
const t6 = Fp12.mul(Fp12.conjugate(Fp12._cyclotomicExp(t5, x)), Fp12._cyclotomicSquare(t2));
const t7 = Fp12.conjugate(Fp12._cyclotomicExp(t6, x));
const t2_t5_pow_q2 = Fp12.frobeniusMap(Fp12.mul(t2, t5), 2);
const t4_t1_pow_q3 = Fp12.frobeniusMap(Fp12.mul(t4, t1), 3);
const t6_t1c_pow_q1 = Fp12.frobeniusMap(Fp12.mul(t6, Fp12.conjugate(t1)), 1);
const t7_t3c_t1 = Fp12.mul(Fp12.mul(t7, Fp12.conjugate(t3)), t1);
// (t2 * t5)^(q²) * (t4 * t1)^(q³) * (t6 * t1.conj)^(q^1) * t7 * t3.conj * t1
return Fp12.mul(Fp12.mul(Fp12.mul(t2_t5_pow_q2, t4_t1_pow_q3), t6_t1c_pow_q1), t7_t3c_t1);
},
});
// Finite field over r.
// This particular field is not used anywhere in bls12-381, but it is still useful.
const Fr = mod.Field(BigInt('0x73eda753299d7d483339d80809a1d80553bda402fffe5bfeffffffff00000001'));
// END OF CURVE FIELDS
// HashToCurve
// 3-isogeny map from E' to E https://www.rfc-editor.org/rfc/rfc9380#appendix-E.3
const isogenyMapG2 = isogenyMap(Fp2, [
// xNum
[
[
'0x5c759507e8e333ebb5b7a9a47d7ed8532c52d39fd3a042a88b58423c50ae15d5c2638e343d9c71c6238aaaaaaaa97d6',
'0x5c759507e8e333ebb5b7a9a47d7ed8532c52d39fd3a042a88b58423c50ae15d5c2638e343d9c71c6238aaaaaaaa97d6',
],
[
'0x0',
'0x11560bf17baa99bc32126fced787c88f984f87adf7ae0c7f9a208c6b4f20a4181472aaa9cb8d555526a9ffffffffc71a',
],
[
'0x11560bf17baa99bc32126fced787c88f984f87adf7ae0c7f9a208c6b4f20a4181472aaa9cb8d555526a9ffffffffc71e',
'0x8ab05f8bdd54cde190937e76bc3e447cc27c3d6fbd7063fcd104635a790520c0a395554e5c6aaaa9354ffffffffe38d',
],
[
'0x171d6541fa38ccfaed6dea691f5fb614cb14b4e7f4e810aa22d6108f142b85757098e38d0f671c7188e2aaaaaaaa5ed1',
'0x0',
],
],
// xDen
[
[
'0x0',
'0x1a0111ea397fe69a4b1ba7b6434bacd764774b84f38512bf6730d2a0f6b0f6241eabfffeb153ffffb9feffffffffaa63',
],
[
'0xc',
'0x1a0111ea397fe69a4b1ba7b6434bacd764774b84f38512bf6730d2a0f6b0f6241eabfffeb153ffffb9feffffffffaa9f',
],
['0x1', '0x0'], // LAST 1
],
// yNum
[
[
'0x1530477c7ab4113b59a4c18b076d11930f7da5d4a07f649bf54439d87d27e500fc8c25ebf8c92f6812cfc71c71c6d706',
'0x1530477c7ab4113b59a4c18b076d11930f7da5d4a07f649bf54439d87d27e500fc8c25ebf8c92f6812cfc71c71c6d706',
],
[
'0x0',
'0x5c759507e8e333ebb5b7a9a47d7ed8532c52d39fd3a042a88b58423c50ae15d5c2638e343d9c71c6238aaaaaaaa97be',
],
[
'0x11560bf17baa99bc32126fced787c88f984f87adf7ae0c7f9a208c6b4f20a4181472aaa9cb8d555526a9ffffffffc71c',
'0x8ab05f8bdd54cde190937e76bc3e447cc27c3d6fbd7063fcd104635a790520c0a395554e5c6aaaa9354ffffffffe38f',
],
[
'0x124c9ad43b6cf79bfbf7043de3811ad0761b0f37a1e26286b0e977c69aa274524e79097a56dc4bd9e1b371c71c718b10',
'0x0',
],
],
// yDen
[
[
'0x1a0111ea397fe69a4b1ba7b6434bacd764774b84f38512bf6730d2a0f6b0f6241eabfffeb153ffffb9feffffffffa8fb',
'0x1a0111ea397fe69a4b1ba7b6434bacd764774b84f38512bf6730d2a0f6b0f6241eabfffeb153ffffb9feffffffffa8fb',
],
[
'0x0',
'0x1a0111ea397fe69a4b1ba7b6434bacd764774b84f38512bf6730d2a0f6b0f6241eabfffeb153ffffb9feffffffffa9d3',
],
[
'0x12',
'0x1a0111ea397fe69a4b1ba7b6434bacd764774b84f38512bf6730d2a0f6b0f6241eabfffeb153ffffb9feffffffffaa99',
],
['0x1', '0x0'], // LAST 1
],
].map((i) => i.map((pair) => Fp2.fromBigTuple(pair.map(BigInt)))));
// 11-isogeny map from E' to E
const isogenyMapG1 = isogenyMap(Fp, [
// xNum
[
'0x11a05f2b1e833340b809101dd99815856b303e88a2d7005ff2627b56cdb4e2c85610c2d5f2e62d6eaeac1662734649b7',
'0x17294ed3e943ab2f0588bab22147a81c7c17e75b2f6a8417f565e33c70d1e86b4838f2a6f318c356e834eef1b3cb83bb',
'0xd54005db97678ec1d1048c5d10a9a1bce032473295983e56878e501ec68e25c958c3e3d2a09729fe0179f9dac9edcb0',
'0x1778e7166fcc6db74e0609d307e55412d7f5e4656a8dbf25f1b33289f1b330835336e25ce3107193c5b388641d9b6861',
'0xe99726a3199f4436642b4b3e4118e5499db995a1257fb3f086eeb65982fac18985a286f301e77c451154ce9ac8895d9',
'0x1630c3250d7313ff01d1201bf7a74ab5db3cb17dd952799b9ed3ab9097e68f90a0870d2dcae73d19cd13c1c66f652983',
'0xd6ed6553fe44d296a3726c38ae652bfb11586264f0f8ce19008e218f9c86b2a8da25128c1052ecaddd7f225a139ed84',
'0x17b81e7701abdbe2e8743884d1117e53356de5ab275b4db1a682c62ef0f2753339b7c8f8c8f475af9ccb5618e3f0c88e',
'0x80d3cf1f9a78fc47b90b33563be990dc43b756ce79f5574a2c596c928c5d1de4fa295f296b74e956d71986a8497e317',
'0x169b1f8e1bcfa7c42e0c37515d138f22dd2ecb803a0c5c99676314baf4bb1b7fa3190b2edc0327797f241067be390c9e',
'0x10321da079ce07e272d8ec09d2565b0dfa7dccdde6787f96d50af36003b14866f69b771f8c285decca67df3f1605fb7b',
'0x6e08c248e260e70bd1e962381edee3d31d79d7e22c837bc23c0bf1bc24c6b68c24b1b80b64d391fa9c8ba2e8ba2d229',
],
// xDen
[
'0x8ca8d548cff19ae18b2e62f4bd3fa6f01d5ef4ba35b48ba9c9588617fc8ac62b558d681be343df8993cf9fa40d21b1c',
'0x12561a5deb559c4348b4711298e536367041e8ca0cf0800c0126c2588c48bf5713daa8846cb026e9e5c8276ec82b3bff',
'0xb2962fe57a3225e8137e629bff2991f6f89416f5a718cd1fca64e00b11aceacd6a3d0967c94fedcfcc239ba5cb83e19',
'0x3425581a58ae2fec83aafef7c40eb545b08243f16b1655154cca8abc28d6fd04976d5243eecf5c4130de8938dc62cd8',
'0x13a8e162022914a80a6f1d5f43e7a07dffdfc759a12062bb8d6b44e833b306da9bd29ba81f35781d539d395b3532a21e',
'0xe7355f8e4e667b955390f7f0506c6e9395735e9ce9cad4d0a43bcef24b8982f7400d24bc4228f11c02df9a29f6304a5',
'0x772caacf16936190f3e0c63e0596721570f5799af53a1894e2e073062aede9cea73b3538f0de06cec2574496ee84a3a',
'0x14a7ac2a9d64a8b230b3f5b074cf01996e7f63c21bca68a81996e1cdf9822c580fa5b9489d11e2d311f7d99bbdcc5a5e',
'0xa10ecf6ada54f825e920b3dafc7a3cce07f8d1d7161366b74100da67f39883503826692abba43704776ec3a79a1d641',
'0x95fc13ab9e92ad4476d6e3eb3a56680f682b4ee96f7d03776df533978f31c1593174e4b4b7865002d6384d168ecdd0a',
'0x000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000001', // LAST 1
],
// yNum
[
'0x90d97c81ba24ee0259d1f094980dcfa11ad138e48a869522b52af6c956543d3cd0c7aee9b3ba3c2be9845719707bb33',
'0x134996a104ee5811d51036d776fb46831223e96c254f383d0f906343eb67ad34d6c56711962fa8bfe097e75a2e41c696',
'0xcc786baa966e66f4a384c86a3b49942552e2d658a31ce2c344be4b91400da7d26d521628b00523b8dfe240c72de1f6',
'0x1f86376e8981c217898751ad8746757d42aa7b90eeb791c09e4a3ec03251cf9de405aba9ec61deca6355c77b0e5f4cb',
'0x8cc03fdefe0ff135caf4fe2a21529c4195536fbe3ce50b879833fd221351adc2ee7f8dc099040a841b6daecf2e8fedb',
'0x16603fca40634b6a2211e11db8f0a6a074a7d0d4afadb7bd76505c3d3ad5544e203f6326c95a807299b23ab13633a5f0',
'0x4ab0b9bcfac1bbcb2c977d027796b3ce75bb8ca2be184cb5231413c4d634f3747a87ac2460f415ec961f8855fe9d6f2',
'0x987c8d5333ab86fde9926bd2ca6c674170a05bfe3bdd81ffd038da6c26c842642f64550fedfe935a15e4ca31870fb29',
'0x9fc4018bd96684be88c9e221e4da1bb8f3abd16679dc26c1e8b6e6a1f20cabe69d65201c78607a360370e577bdba587',
'0xe1bba7a1186bdb5223abde7ada14a23c42a0ca7915af6fe06985e7ed1e4d43b9b3f7055dd4eba6f2bafaaebca731c30',
'0x19713e47937cd1be0dfd0b8f1d43fb93cd2fcbcb6caf493fd1183e416389e61031bf3a5cce3fbafce813711ad011c132',
'0x18b46a908f36f6deb918c143fed2edcc523559b8aaf0c2462e6bfe7f911f643249d9cdf41b44d606ce07c8a4d0074d8e',
'0xb182cac101b9399d155096004f53f447aa7b12a3426b08ec02710e807b4633f06c851c1919211f20d4c04f00b971ef8',
'0x245a394ad1eca9b72fc00ae7be315dc757b3b080d4c158013e6632d3c40659cc6cf90ad1c232a6442d9d3f5db980133',
'0x5c129645e44cf1102a159f748c4a3fc5e673d81d7e86568d9ab0f5d396a7ce46ba1049b6579afb7866b1e715475224b',
'0x15e6be4e990f03ce4ea50b3b42df2eb5cb181d8f84965a3957add4fa95af01b2b665027efec01c7704b456be69c8b604',
],
// yDen
[
'0x16112c4c3a9c98b252181140fad0eae9601a6de578980be6eec3232b5be72e7a07f3688ef60c206d01479253b03663c1',
'0x1962d75c2381201e1a0cbd6c43c348b885c84ff731c4d59ca4a10356f453e01f78a4260763529e3532f6102c2e49a03d',
'0x58df3306640da276faaae7d6e8eb15778c4855551ae7f310c35a5dd279cd2eca6757cd636f96f891e2538b53dbf67f2',
'0x16b7d288798e5395f20d23bf89edb4d1d115c5dbddbcd30e123da489e726af41727364f2c28297ada8d26d98445f5416',
'0xbe0e079545f43e4b00cc912f8228ddcc6d19c9f0f69bbb0542eda0fc9dec916a20b15dc0fd2ededda39142311a5001d',
'0x8d9e5297186db2d9fb266eaac783182b70152c65550d881c5ecd87b6f0f5a6449f38db9dfa9cce202c6477faaf9b7ac',
'0x166007c08a99db2fc3ba8734ace9824b5eecfdfa8d0cf8ef5dd365bc400a0051d5fa9c01a58b1fb93d1a1399126a775c',
'0x16a3ef08be3ea7ea03bcddfabba6ff6ee5a4375efa1f4fd7feb34fd206357132b920f5b00801dee460ee415a15812ed9',
'0x1866c8ed336c61231a1be54fd1d74cc4f9fb0ce4c6af5920abc5750c4bf39b4852cfe2f7bb9248836b233d9d55535d4a',
'0x167a55cda70a6e1cea820597d94a84903216f763e13d87bb5308592e7ea7d4fbc7385ea3d529b35e346ef48bb8913f55',
'0x4d2f259eea405bd48f010a01ad2911d9c6dd039bb61a6290e591b36e636a5c871a5c29f4f83060400f8b49cba8f6aa8',
'0xaccbb67481d033ff5852c1e48c50c477f94ff8aefce42d28c0f9a88cea7913516f968986f7ebbea9684b529e2561092',
'0xad6b9514c767fe3c3613144b45f1496543346d98adf02267d5ceef9a00d9b8693000763e3b90ac11e99b138573345cc',
'0x2660400eb2e4f3b628bdd0d53cd76f2bf565b94e72927c1cb748df27942480e420517bd8714cc80d1fadc1326ed06f7',
'0xe0fa1d816ddc03e6b24255e0d7819c171c40f65e273b853324efcd6356caa205ca2f570f13497804415473a1d634b8f',
'0x000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000001', // LAST 1
],
].map((i) => i.map((j) => BigInt(j))));
// SWU Map - Fp2 to G2': y² = x³ + 240i * x + 1012 + 1012i
const G2_SWU = mapToCurveSimpleSWU(Fp2, {
A: Fp2.create({ c0: Fp.create(_0n), c1: Fp.create(BigInt(240)) }), // A' = 240 * I
B: Fp2.create({ c0: Fp.create(BigInt(1012)), c1: Fp.create(BigInt(1012)) }), // B' = 1012 * (1 + I)
Z: Fp2.create({ c0: Fp.create(BigInt(-2)), c1: Fp.create(BigInt(-1)) }), // Z: -(2 + I)
});
// Optimized SWU Map - Fp to G1
const G1_SWU = mapToCurveSimpleSWU(Fp, {
A: Fp.create(BigInt('0x144698a3b8e9433d693a02c96d4982b0ea985383ee66a8d8e8981aefd881ac98936f8da0e0f97f5cf428082d584c1d')),
B: Fp.create(BigInt('0x12e2908d11688030018b12e8753eee3b2016c1f0f24f4070a0b9c14fcef35ef55a23215a316ceaa5d1cc48e98e172be0')),
Z: Fp.create(BigInt(11)),
});
// Endomorphisms (for fast cofactor clearing)
// Ψ(P) endomorphism
const { G2psi, G2psi2 } = psiFrobenius(Fp, Fp2, Fp2.div(Fp2.ONE, Fp2.NONRESIDUE)); // 1/(u+1)
// Default hash_to_field options are for hash to G2.
//
// Parameter definitions are in section 5.3 of the spec unless otherwise noted.
// Parameter values come from section 8.8.2 of the spec.
// https://www.rfc-editor.org/rfc/rfc9380#section-8.8.2
//
// Base field F is GF(p^m)
// p = 0x1a0111ea397fe69a4b1ba7b6434bacd764774b84f38512bf6730d2a0f6b0f6241eabfffeb153ffffb9feffffffffaaab
// m = 2 (or 1 for G1 see section 8.8.1)
// k = 128
const htfDefaults = Object.freeze({
// DST: a domain separation tag
// defined in section 2.2.5
// Use utils.getDSTLabel(), utils.setDSTLabel(value)
DST: 'BLS_SIG_BLS12381G2_XMD:SHA-256_SSWU_RO_NUL_',
encodeDST: 'BLS_SIG_BLS12381G2_XMD:SHA-256_SSWU_RO_NUL_',
// p: the characteristic of F
// where F is a finite field of characteristic p and order q = p^m
p: Fp.ORDER,
// m: the extension degree of F, m >= 1
// where F is a finite field of characteristic p and order q = p^m
m: 2,
// k: the target security level for the suite in bits
// defined in section 5.1
k: 128,
// option to use a message that has already been processed by
// expand_message_xmd
expand: 'xmd',
// Hash functions for: expand_message_xmd is appropriate for use with a
// wide range of hash functions, including SHA-2, SHA-3, BLAKE2, and others.
// BBS+ uses blake2: https://github.com/hyperledger/aries-framework-go/issues/2247
hash: sha256,
});
// Encoding utils
// Point on G1 curve: (x, y)
// Compressed point of infinity
const COMPRESSED_ZERO = setMask(Fp.toBytes(_0n), { infinity: true, compressed: true }); // set compressed & point-at-infinity bits
function parseMask(bytes) {
// Copy, so we can remove mask data. It will be removed also later, when Fp.create will call modulo.
bytes = bytes.slice();
const mask = bytes[0] & 224;
const compressed = !!((mask >> 7) & 1); // compression bit (0b1000_0000)
const infinity = !!((mask >> 6) & 1); // point at infinity bit (0b0100_0000)
const sort = !!((mask >> 5) & 1); // sort bit (0b0010_0000)
bytes[0] &= 31; // clear mask (zero first 3 bits)
return { compressed, infinity, sort, value: bytes };
}
function setMask(bytes, mask) {
if (bytes[0] & 224)
throw new Error('setMask: non-empty mask');
if (mask.compressed)
bytes[0] |= 128;
if (mask.infinity)
bytes[0] |= 64;
if (mask.sort)
bytes[0] |= 32;
return bytes;
}
function signatureG1ToRawBytes(point) {
point.assertValidity();
const isZero = point.equals(bls12_381.G1.ProjectivePoint.ZERO);
const { x, y } = point.toAffine();
if (isZero)
return COMPRESSED_ZERO.slice();
const P = Fp.ORDER;
const sort = Boolean((y * _2n) / P);
return setMask(numberToBytesBE(x, Fp.BYTES), { compressed: true, sort });
}
function signatureG2ToRawBytes(point) {
// NOTE: by some reasons it was missed in bls12-381, looks like bug
point.assertValidity();
const len = Fp.BYTES;
if (point.equals(bls12_381.G2.ProjectivePoint.ZERO))
return concatB(COMPRESSED_ZERO, numberToBytesBE(_0n, len));
const { x, y } = point.toAffine();
const { re: x0, im: x1 } = Fp2.reim(x);
const { re: y0, im: y1 } = Fp2.reim(y);
const tmp = y1 > _0n ? y1 * _2n : y0 * _2n;
const sort = Boolean((tmp / Fp.ORDER) & _1n);
const z2 = x0;
return concatB(setMask(numberToBytesBE(x1, len), { sort, compressed: true }), numberToBytesBE(z2, len));
}
/**
* bls12-381 pairing-friendly curve.
* @example
* import { bls12_381 as bls } from '@noble/curves/bls12-381';
* // G1 keys, G2 signatures
* const privateKey = '67d53f170b908cabb9eb326c3c337762d59289a8fec79f7bc9254b584b73265c';
* const message = '64726e3da8';
* const publicKey = bls.getPublicKey(privateKey);
* const signature = bls.sign(message, privateKey);
* const isValid = bls.verify(signature, message, publicKey);
*/
export const bls12_381 = bls({
// Fields
fields: {
Fp,
Fp2,
Fp6,
Fp12,
Fr,
},
// G1 is the order-q subgroup of E1(Fp) : y² = x³ + 4, #E1(Fp) = h1q, where
// characteristic; z + (z⁴ - z² + 1)(z - 1)²/3
G1: {
Fp,
// cofactor; (z - 1)²/3
h: BigInt('0x396c8c005555e1568c00aaab0000aaab'),
// generator's coordinates
// x = 3685416753713387016781088315183077757961620795782546409894578378688607592378376318836054947676345821548104185464507
// y = 1339506544944476473020471379941921221584933875938349620426543736416511423956333506472724655353366534992391756441569
Gx: BigInt('0x17f1d3a73197d7942695638c4fa9ac0fc3688c4f9774b905a14e3a3f171bac586c55e83ff97a1aeffb3af00adb22c6bb'),
Gy: BigInt('0x08b3f481e3aaa0f1a09e30ed741d8ae4fcf5e095d5d00af600db18cb2c04b3edd03cc744a2888ae40caa232946c5e7e1'),
a: Fp.ZERO,
b: _4n,
htfDefaults: { ...htfDefaults, m: 1, DST: 'BLS_SIG_BLS12381G1_XMD:SHA-256_SSWU_RO_NUL_' },
wrapPrivateKey: true,
allowInfinityPoint: true,
// Checks is the point resides in prime-order subgroup.
// point.isTorsionFree() should return true for valid points
// It returns false for shitty points.
// https://eprint.iacr.org/2021/1130.pdf
isTorsionFree: (c, point) => {
// φ endomorphism
const cubicRootOfUnityModP = BigInt('0x5f19672fdf76ce51ba69c6076a0f77eaddb3a93be6f89688de17d813620a00022e01fffffffefffe');
const phi = new c(Fp.mul(point.px, cubicRootOfUnityModP), point.py, point.pz);
// todo: unroll
const xP = point.multiplyUnsafe(BLS_X).negate(); // [x]P
const u2P = xP.multiplyUnsafe(BLS_X); // [u2]P
return u2P.equals(phi);
// https://eprint.iacr.org/2019/814.pdf
// (z² − 1)/3
// const c1 = BigInt('0x396c8c005555e1560000000055555555');
// const P = this;
// const S = P.sigma();
// const Q = S.double();
// const S2 = S.sigma();
// // [(z² − 1)/3](2σ(P) − P − σ²(P)) − σ²(P) = O
// const left = Q.subtract(P).subtract(S2).multiplyUnsafe(c1);
// const C = left.subtract(S2);
// return C.isZero();
},
// Clear cofactor of G1
// https://eprint.iacr.org/2019/403
clearCofactor: (_c, point) => {
// return this.multiplyUnsafe(CURVE.h);
return point.multiplyUnsafe(BLS_X).add(point); // x*P + P
},
mapToCurve: (scalars) => {
const { x, y } = G1_SWU(Fp.create(scalars[0]));
return isogenyMapG1(x, y);
},
fromBytes: (bytes) => {
const { compressed, infinity, sort, value } = parseMask(bytes);
if (value.length === 48 && compressed) {
// TODO: Fp.bytes
const P = Fp.ORDER;
const compressedValue = bytesToNumberBE(value);
// Zero
const x = Fp.create(compressedValue & Fp.MASK);
if (infinity) {
if (x !== _0n)
throw new Error('G1: non-empty compressed point at infinity');
return { x: _0n, y: _0n };
}
const right = Fp.add(Fp.pow(x, _3n), Fp.create(bls12_381.params.G1b)); // y² = x³ + b
let y = Fp.sqrt(right);
if (!y)
throw new Error('invalid compressed G1 point');
if ((y * _2n) / P !== BigInt(sort))
y = Fp.neg(y);
return { x: Fp.create(x), y: Fp.create(y) };
}
else if (value.length === 96 && !compressed) {
// Check if the infinity flag is set
const x = bytesToNumberBE(value.subarray(0, Fp.BYTES));
const y = bytesToNumberBE(value.subarray(Fp.BYTES));
if (infinity) {
if (x !== _0n || y !== _0n)
throw new Error('G1: non-empty point at infinity');
return bls12_381.G1.ProjectivePoint.ZERO.toAffine();
}
return { x: Fp.create(x), y: Fp.create(y) };
}
else {
throw new Error('invalid point G1, expected 48/96 bytes');
}
},
toBytes: (c, point, isCompressed) => {
const isZero = point.equals(c.ZERO);
const { x, y } = point.toAffine();
if (isCompressed) {
if (isZero)
return COMPRESSED_ZERO.slice();
const P = Fp.ORDER;
const sort = Boolean((y * _2n) / P);
return setMask(numberToBytesBE(x, Fp.BYTES), { compressed: true, sort });
}
else {
if (isZero) {
// 2x PUBLIC_KEY_LENGTH
const x = concatB(new Uint8Array([0x40]), new Uint8Array(2 * Fp.BYTES - 1));
return x;
}
else {
return concatB(numberToBytesBE(x, Fp.BYTES), numberToBytesBE(y, Fp.BYTES));
}
}
},
ShortSignature: {
fromHex(hex) {
const { infinity, sort, value } = parseMask(ensureBytes('signatureHex', hex, 48));
const P = Fp.ORDER;
const compressedValue = bytesToNumberBE(value);
// Zero
if (infinity)
return bls12_381.G1.ProjectivePoint.ZERO;
const x = Fp.create(compressedValue & Fp.MASK);
const right = Fp.add(Fp.pow(x, _3n), Fp.create(bls12_381.params.G1b)); // y² = x³ + b
let y = Fp.sqrt(right);
if (!y)
throw new Error('invalid compressed G1 point');
const aflag = BigInt(sort);
if ((y * _2n) / P !== aflag)
y = Fp.neg(y);
const point = bls12_381.G1.ProjectivePoint.fromAffine({ x, y });
point.assertValidity();
return point;
},
toRawBytes(point) {
return signatureG1ToRawBytes(point);
},
toHex(point) {
return bytesToHex(signatureG1ToRawBytes(point));
},
},
},
// G2 is the order-q subgroup of E2(Fp²) : y² = x³+4(1+√−1),
// where Fp2 is Fp[√−1]/(x2+1). #E2(Fp2 ) = h2q, where
// G² - 1
// h2q
G2: {
Fp: Fp2,
// cofactor
h: BigInt('0x5d543a95414e7f1091d50792876a202cd91de4547085abaa68a205b2e5a7ddfa628f1cb4d9e82ef21537e293a6691ae1616ec6e786f0c70cf1c38e31c7238e5'),
Gx: Fp2.fromBigTuple([
BigInt('0x024aa2b2f08f0a91260805272dc51051c6e47ad4fa403b02b4510b647ae3d1770bac0326a805bbefd48056c8c121bdb8'),
BigInt('0x13e02b6052719f607dacd3a088274f65596bd0d09920b61ab5da61bbdc7f5049334cf11213945d57e5ac7d055d042b7e'),
]),
// y =
// 927553665492332455747201965776037880757740193453592970025027978793976877002675564980949289727957565575433344219582,
// 1985150602287291935568054521177171638300868978215655730859378665066344726373823718423869104263333984641494340347905
Gy: Fp2.fromBigTuple([
BigInt('0x0ce5d527727d6e118cc9cdc6da2e351aadfd9baa8cbdd3a76d429a695160d12c923ac9cc3baca289e193548608b82801'),
BigInt('0x0606c4a02ea734cc32acd2b02bc28b99cb3e287e85a763af267492ab572e99ab3f370d275cec1da1aaa9075ff05f79be'),
]),
a: Fp2.ZERO,
b: Fp2.fromBigTuple([_4n, _4n]),
hEff: BigInt('0xbc69f08f2ee75b3584c6a0ea91b352888e2a8e9145ad7689986ff031508ffe1329c2f178731db956d82bf015d1212b02ec0ec69d7477c1ae954cbc06689f6a359894c0adebbf6b4e8020005aaa95551'),
htfDefaults: { ...htfDefaults },
wrapPrivateKey: true,
allowInfinityPoint: true,
mapToCurve: (scalars) => {
const { x, y } = G2_SWU(Fp2.fromBigTuple(scalars));
return isogenyMapG2(x, y);
},
// Checks is the point resides in prime-order subgroup.
// point.isTorsionFree() should return true for valid points
// It returns false for shitty points.
// https://eprint.iacr.org/2021/1130.pdf
isTorsionFree: (c, P) => {
return P.multiplyUnsafe(BLS_X).negate().equals(G2psi(c, P)); // ψ(P) == [u](P)
// Older version: https://eprint.iacr.org/2019/814.pdf
// Ψ²(P) => Ψ³(P) => [z]Ψ³(P) where z = -x => [z]Ψ³(P) - Ψ²(P) + P == O
// return P.psi2().psi().mulNegX().subtract(psi2).add(P).isZero();
},
// Maps the point into the prime-order subgroup G2.
// clear_cofactor_bls12381_g2 from cfrg-hash-to-curve-11
// https://eprint.iacr.org/2017/419.pdf
// prettier-ignore
clearCofactor: (c, P) => {
const x = BLS_X;
let t1 = P.multiplyUnsafe(x).negate(); // [-x]P
let t2 = G2psi(c, P); // Ψ(P)
let t3 = P.double(); // 2P
t3 = G2psi2(c, t3); // Ψ²(2P)
t3 = t3.subtract(t2); // Ψ²(2P) - Ψ(P)
t2 = t1.add(t2); // [-x]P + Ψ(P)
t2 = t2.multiplyUnsafe(x).negate(); // [x²]P - [x]Ψ(P)
t3 = t3.add(t2); // Ψ²(2P) - Ψ(P) + [x²]P - [x]Ψ(P)
t3 = t3.subtract(t1); // Ψ²(2P) - Ψ(P) + [x²]P - [x]Ψ(P) + [x]P
const Q = t3.subtract(P); // Ψ²(2P) - Ψ(P) + [x²]P - [x]Ψ(P) + [x]P - 1P
return Q; // [x²-x-1]P + [x-1]Ψ(P) + Ψ²(2P)
},
fromBytes: (bytes) => {
const { compressed, infinity, sort, value } = parseMask(bytes);
if ((!compressed && !infinity && sort) || // 00100000
(!compressed && infinity && sort) || // 01100000
(sort && infinity && compressed) // 11100000
) {
throw new Error('invalid encoding flag: ' + (bytes[0] & 224));
}
const L = Fp.BYTES;
const slc = (b, from, to) => bytesToNumberBE(b.slice(from, to));
if (value.length === 96 && compressed) {
const b = bls12_381.params.G2b;
const P = Fp.ORDER;
if (infinity) {
// check that all bytes are 0
if (value.reduce((p, c) => (p !== 0 ? c + 1 : c), 0) > 0) {
throw new Error('invalid compressed G2 point');
}
return { x: Fp2.ZERO, y: Fp2.ZERO };
}
const x_1 = slc(value, 0, L);
const x_0 = slc(value, L, 2 * L);
const x = Fp2.create({ c0: Fp.create(x_0), c1: Fp.create(x_1) });
const right = Fp2.add(Fp2.pow(x, _3n), b); // y² = x³ + 4 * (u+1) = x³ + b
let y = Fp2.sqrt(right);
const Y_bit = y.c1 === _0n ? (y.c0 * _2n) / P : (y.c1 * _2n) / P ? _1n : _0n;
y = sort && Y_bit > 0 ? y : Fp2.neg(y);
return { x, y };
}
else if (value.length === 192 && !compressed) {
if (infinity) {
if (value.reduce((p, c) => (p !== 0 ? c + 1 : c), 0) > 0) {
throw new Error('invalid uncompressed G2 point');
}
return { x: Fp2.ZERO, y: Fp2.ZERO };
}
const x1 = slc(value, 0, L);
const x0 = slc(value, L, 2 * L);
const y1 = slc(value, 2 * L, 3 * L);
const y0 = slc(value, 3 * L, 4 * L);
return { x: Fp2.fromBigTuple([x0, x1]), y: Fp2.fromBigTuple([y0, y1]) };
}
else {
throw new Error('invalid point G2, expected 96/192 bytes');
}
},
toBytes: (c, point, isCompressed) => {
const { BYTES: len, ORDER: P } = Fp;
const isZero = point.equals(c.ZERO);
const { x, y } = point.toAffine();
if (isCompressed) {
if (isZero)
return concatB(COMPRESSED_ZERO, numberToBytesBE(_0n, len));
const flag = Boolean(y.c1 === _0n ? (y.c0 * _2n) / P : (y.c1 * _2n) / P);
return concatB(setMask(numberToBytesBE(x.c1, len), { compressed: true, sort: flag }), numberToBytesBE(x.c0, len));
}
else {
if (isZero)
return concatB(new Uint8Array([0x40]), new Uint8Array(4 * len - 1)); // bytes[0] |= 1 << 6;
const { re: x0, im: x1 } = Fp2.reim(x);
const { re: y0, im: y1 } = Fp2.reim(y);
return concatB(numberToBytesBE(x1, len), numberToBytesBE(x0, len), numberToBytesBE(y1, len), numberToBytesBE(y0, len));
}
},
Signature: {
// TODO: Optimize, it's very slow because of sqrt.
fromHex(hex) {
const { infinity, sort, value } = parseMask(ensureBytes('signatureHex', hex));
const P = Fp.ORDER;
const half = value.length / 2;
if (half !== 48 && half !== 96)
throw new Error('invalid compressed signature length, must be 96 or 192');
const z1 = bytesToNumberBE(value.slice(0, half));
const z2 = bytesToNumberBE(value.slice(half));
// Indicates the infinity point
if (infinity)
return bls12_381.G2.ProjectivePoint.ZERO;
const x1 = Fp.create(z1 & Fp.MASK);
const x2 = Fp.create(z2);
const x = Fp2.create({ c0: x2, c1: x1 });
const y2 = Fp2.add(Fp2.pow(x, _3n), bls12_381.params.G2b); // y² = x³ + 4
// The slow part
let y = Fp2.sqrt(y2);
if (!y)
throw new Error('Failed to find a square root');
// Choose the y whose leftmost bit of the imaginary part is equal to the a_flag1
// If y1 happens to be zero, then use the bit of y0
const { re: y0, im: y1 } = Fp2.reim(y);
const aflag1 = BigInt(sort);
const isGreater = y1 > _0n && (y1 * _2n) / P !== aflag1;
const isZero = y1 === _0n && (y0 * _2n) / P !== aflag1;
if (isGreater || isZero)
y = Fp2.neg(y);
const point = bls12_381.G2.ProjectivePoint.fromAffine({ x, y });
point.assertValidity();
return point;
},
toRawBytes(point) {
return signatureG2ToRawBytes(point);
},
toHex(point) {
return bytesToHex(signatureG2ToRawBytes(point));
},
},
},
params: {
ateLoopSize: BLS_X, // The BLS parameter x for BLS12-381
r: Fr.ORDER, // order; z⁴ − z² + 1; CURVE.n from other curves
xNegative: true,
twistType: 'multiplicative',
},
htfDefaults,
hash: sha256,
randomBytes,
});
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