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- import { mod } from './modular.js';
- import { abytes, bytesToNumberBE, concatBytes, utf8ToBytes, validateObject } from './utils.js';
- // Octet Stream to Integer. "spec" implementation of os2ip is 2.5x slower vs bytesToNumberBE.
- const os2ip = bytesToNumberBE;
- // Integer to Octet Stream (numberToBytesBE)
- function i2osp(value, length) {
- if (value < 0 || value >= 1 << (8 * length)) {
- throw new Error(`bad I2OSP call: value=${value} length=${length}`);
- }
- const res = Array.from({ length }).fill(0);
- for (let i = length - 1; i >= 0; i--) {
- res[i] = value & 0xff;
- value >>>= 8;
- }
- return new Uint8Array(res);
- }
- function strxor(a, b) {
- const arr = new Uint8Array(a.length);
- for (let i = 0; i < a.length; i++) {
- arr[i] = a[i] ^ b[i];
- }
- return arr;
- }
- function anum(item) {
- if (!Number.isSafeInteger(item))
- throw new Error('number expected');
- }
- // Produces a uniformly random byte string using a cryptographic hash function H that outputs b bits
- // https://www.rfc-editor.org/rfc/rfc9380#section-5.3.1
- export function expand_message_xmd(msg, DST, lenInBytes, H) {
- abytes(msg);
- abytes(DST);
- anum(lenInBytes);
- // https://www.rfc-editor.org/rfc/rfc9380#section-5.3.3
- if (DST.length > 255)
- DST = H(concatBytes(utf8ToBytes('H2C-OVERSIZE-DST-'), DST));
- const { outputLen: b_in_bytes, blockLen: r_in_bytes } = H;
- const ell = Math.ceil(lenInBytes / b_in_bytes);
- if (ell > 255)
- throw new Error('Invalid xmd length');
- const DST_prime = concatBytes(DST, i2osp(DST.length, 1));
- const Z_pad = i2osp(0, r_in_bytes);
- const l_i_b_str = i2osp(lenInBytes, 2); // len_in_bytes_str
- const b = new Array(ell);
- const b_0 = H(concatBytes(Z_pad, msg, l_i_b_str, i2osp(0, 1), DST_prime));
- b[0] = H(concatBytes(b_0, i2osp(1, 1), DST_prime));
- for (let i = 1; i <= ell; i++) {
- const args = [strxor(b_0, b[i - 1]), i2osp(i + 1, 1), DST_prime];
- b[i] = H(concatBytes(...args));
- }
- const pseudo_random_bytes = concatBytes(...b);
- return pseudo_random_bytes.slice(0, lenInBytes);
- }
- // Produces a uniformly random byte string using an extendable-output function (XOF) H.
- // 1. The collision resistance of H MUST be at least k bits.
- // 2. H MUST be an XOF that has been proved indifferentiable from
- // a random oracle under a reasonable cryptographic assumption.
- // https://www.rfc-editor.org/rfc/rfc9380#section-5.3.2
- export function expand_message_xof(msg, DST, lenInBytes, k, H) {
- abytes(msg);
- abytes(DST);
- anum(lenInBytes);
- // https://www.rfc-editor.org/rfc/rfc9380#section-5.3.3
- // DST = H('H2C-OVERSIZE-DST-' || a_very_long_DST, Math.ceil((lenInBytes * k) / 8));
- if (DST.length > 255) {
- const dkLen = Math.ceil((2 * k) / 8);
- DST = H.create({ dkLen }).update(utf8ToBytes('H2C-OVERSIZE-DST-')).update(DST).digest();
- }
- if (lenInBytes > 65535 || DST.length > 255)
- throw new Error('expand_message_xof: invalid lenInBytes');
- return (H.create({ dkLen: lenInBytes })
- .update(msg)
- .update(i2osp(lenInBytes, 2))
- // 2. DST_prime = DST || I2OSP(len(DST), 1)
- .update(DST)
- .update(i2osp(DST.length, 1))
- .digest());
- }
- /**
- * Hashes arbitrary-length byte strings to a list of one or more elements of a finite field F
- * https://www.rfc-editor.org/rfc/rfc9380#section-5.2
- * @param msg a byte string containing the message to hash
- * @param count the number of elements of F to output
- * @param options `{DST: string, p: bigint, m: number, k: number, expand: 'xmd' | 'xof', hash: H}`, see above
- * @returns [u_0, ..., u_(count - 1)], a list of field elements.
- */
- export function hash_to_field(msg, count, options) {
- validateObject(options, {
- DST: 'stringOrUint8Array',
- p: 'bigint',
- m: 'isSafeInteger',
- k: 'isSafeInteger',
- hash: 'hash',
- });
- const { p, k, m, hash, expand, DST: _DST } = options;
- abytes(msg);
- anum(count);
- const DST = typeof _DST === 'string' ? utf8ToBytes(_DST) : _DST;
- const log2p = p.toString(2).length;
- const L = Math.ceil((log2p + k) / 8); // section 5.1 of ietf draft link above
- const len_in_bytes = count * m * L;
- let prb; // pseudo_random_bytes
- if (expand === 'xmd') {
- prb = expand_message_xmd(msg, DST, len_in_bytes, hash);
- }
- else if (expand === 'xof') {
- prb = expand_message_xof(msg, DST, len_in_bytes, k, hash);
- }
- else if (expand === '_internal_pass') {
- // for internal tests only
- prb = msg;
- }
- else {
- throw new Error('expand must be "xmd" or "xof"');
- }
- const u = new Array(count);
- for (let i = 0; i < count; i++) {
- const e = new Array(m);
- for (let j = 0; j < m; j++) {
- const elm_offset = L * (j + i * m);
- const tv = prb.subarray(elm_offset, elm_offset + L);
- e[j] = mod(os2ip(tv), p);
- }
- u[i] = e;
- }
- return u;
- }
- export function isogenyMap(field, map) {
- // Make same order as in spec
- const COEFF = map.map((i) => Array.from(i).reverse());
- return (x, y) => {
- const [xNum, xDen, yNum, yDen] = COEFF.map((val) => val.reduce((acc, i) => field.add(field.mul(acc, x), i)));
- x = field.div(xNum, xDen); // xNum / xDen
- y = field.mul(y, field.div(yNum, yDen)); // y * (yNum / yDev)
- return { x, y };
- };
- }
- export function createHasher(Point, mapToCurve, def) {
- if (typeof mapToCurve !== 'function')
- throw new Error('mapToCurve() must be defined');
- return {
- // Encodes byte string to elliptic curve.
- // hash_to_curve from https://www.rfc-editor.org/rfc/rfc9380#section-3
- hashToCurve(msg, options) {
- const u = hash_to_field(msg, 2, { ...def, DST: def.DST, ...options });
- const u0 = Point.fromAffine(mapToCurve(u[0]));
- const u1 = Point.fromAffine(mapToCurve(u[1]));
- const P = u0.add(u1).clearCofactor();
- P.assertValidity();
- return P;
- },
- // Encodes byte string to elliptic curve.
- // encode_to_curve from https://www.rfc-editor.org/rfc/rfc9380#section-3
- encodeToCurve(msg, options) {
- const u = hash_to_field(msg, 1, { ...def, DST: def.encodeDST, ...options });
- const P = Point.fromAffine(mapToCurve(u[0])).clearCofactor();
- P.assertValidity();
- return P;
- },
- // Same as encodeToCurve, but without hash
- mapToCurve(scalars) {
- if (!Array.isArray(scalars))
- throw new Error('mapToCurve: expected array of bigints');
- for (const i of scalars)
- if (typeof i !== 'bigint')
- throw new Error(`mapToCurve: expected array of bigints, got ${i} in array`);
- const P = Point.fromAffine(mapToCurve(scalars)).clearCofactor();
- P.assertValidity();
- return P;
- },
- };
- }
- //# sourceMappingURL=hash-to-curve.js.map
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