180 lines
7.3 KiB
JavaScript
180 lines
7.3 KiB
JavaScript
"use strict";
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Object.defineProperty(exports, "__esModule", { value: true });
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exports.expand_message_xmd = expand_message_xmd;
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exports.expand_message_xof = expand_message_xof;
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exports.hash_to_field = hash_to_field;
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exports.isogenyMap = isogenyMap;
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exports.createHasher = createHasher;
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const modular_js_1 = require("./modular.js");
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const utils_js_1 = require("./utils.js");
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// Octet Stream to Integer. "spec" implementation of os2ip is 2.5x slower vs bytesToNumberBE.
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const os2ip = utils_js_1.bytesToNumberBE;
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// Integer to Octet Stream (numberToBytesBE)
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function i2osp(value, length) {
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if (value < 0 || value >= 1 << (8 * length)) {
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throw new Error(`bad I2OSP call: value=${value} length=${length}`);
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}
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const res = Array.from({ length }).fill(0);
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for (let i = length - 1; i >= 0; i--) {
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res[i] = value & 0xff;
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value >>>= 8;
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}
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return new Uint8Array(res);
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}
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function strxor(a, b) {
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const arr = new Uint8Array(a.length);
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for (let i = 0; i < a.length; i++) {
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arr[i] = a[i] ^ b[i];
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}
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return arr;
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}
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function anum(item) {
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if (!Number.isSafeInteger(item))
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throw new Error('number expected');
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}
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// Produces a uniformly random byte string using a cryptographic hash function H that outputs b bits
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// https://www.rfc-editor.org/rfc/rfc9380#section-5.3.1
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function expand_message_xmd(msg, DST, lenInBytes, H) {
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(0, utils_js_1.abytes)(msg);
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(0, utils_js_1.abytes)(DST);
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anum(lenInBytes);
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// https://www.rfc-editor.org/rfc/rfc9380#section-5.3.3
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if (DST.length > 255)
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DST = H((0, utils_js_1.concatBytes)((0, utils_js_1.utf8ToBytes)('H2C-OVERSIZE-DST-'), DST));
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const { outputLen: b_in_bytes, blockLen: r_in_bytes } = H;
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const ell = Math.ceil(lenInBytes / b_in_bytes);
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if (ell > 255)
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throw new Error('Invalid xmd length');
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const DST_prime = (0, utils_js_1.concatBytes)(DST, i2osp(DST.length, 1));
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const Z_pad = i2osp(0, r_in_bytes);
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const l_i_b_str = i2osp(lenInBytes, 2); // len_in_bytes_str
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const b = new Array(ell);
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const b_0 = H((0, utils_js_1.concatBytes)(Z_pad, msg, l_i_b_str, i2osp(0, 1), DST_prime));
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b[0] = H((0, utils_js_1.concatBytes)(b_0, i2osp(1, 1), DST_prime));
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for (let i = 1; i <= ell; i++) {
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const args = [strxor(b_0, b[i - 1]), i2osp(i + 1, 1), DST_prime];
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b[i] = H((0, utils_js_1.concatBytes)(...args));
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}
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const pseudo_random_bytes = (0, utils_js_1.concatBytes)(...b);
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return pseudo_random_bytes.slice(0, lenInBytes);
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}
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// Produces a uniformly random byte string using an extendable-output function (XOF) H.
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// 1. The collision resistance of H MUST be at least k bits.
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// 2. H MUST be an XOF that has been proved indifferentiable from
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// a random oracle under a reasonable cryptographic assumption.
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// https://www.rfc-editor.org/rfc/rfc9380#section-5.3.2
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function expand_message_xof(msg, DST, lenInBytes, k, H) {
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(0, utils_js_1.abytes)(msg);
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(0, utils_js_1.abytes)(DST);
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anum(lenInBytes);
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// https://www.rfc-editor.org/rfc/rfc9380#section-5.3.3
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// DST = H('H2C-OVERSIZE-DST-' || a_very_long_DST, Math.ceil((lenInBytes * k) / 8));
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if (DST.length > 255) {
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const dkLen = Math.ceil((2 * k) / 8);
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DST = H.create({ dkLen }).update((0, utils_js_1.utf8ToBytes)('H2C-OVERSIZE-DST-')).update(DST).digest();
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}
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if (lenInBytes > 65535 || DST.length > 255)
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throw new Error('expand_message_xof: invalid lenInBytes');
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return (H.create({ dkLen: lenInBytes })
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.update(msg)
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.update(i2osp(lenInBytes, 2))
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// 2. DST_prime = DST || I2OSP(len(DST), 1)
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.update(DST)
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.update(i2osp(DST.length, 1))
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.digest());
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}
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/**
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* Hashes arbitrary-length byte strings to a list of one or more elements of a finite field F
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* https://www.rfc-editor.org/rfc/rfc9380#section-5.2
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* @param msg a byte string containing the message to hash
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* @param count the number of elements of F to output
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* @param options `{DST: string, p: bigint, m: number, k: number, expand: 'xmd' | 'xof', hash: H}`, see above
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* @returns [u_0, ..., u_(count - 1)], a list of field elements.
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*/
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function hash_to_field(msg, count, options) {
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(0, utils_js_1.validateObject)(options, {
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DST: 'stringOrUint8Array',
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p: 'bigint',
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m: 'isSafeInteger',
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k: 'isSafeInteger',
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hash: 'hash',
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});
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const { p, k, m, hash, expand, DST: _DST } = options;
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(0, utils_js_1.abytes)(msg);
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anum(count);
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const DST = typeof _DST === 'string' ? (0, utils_js_1.utf8ToBytes)(_DST) : _DST;
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const log2p = p.toString(2).length;
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const L = Math.ceil((log2p + k) / 8); // section 5.1 of ietf draft link above
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const len_in_bytes = count * m * L;
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let prb; // pseudo_random_bytes
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if (expand === 'xmd') {
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prb = expand_message_xmd(msg, DST, len_in_bytes, hash);
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}
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else if (expand === 'xof') {
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prb = expand_message_xof(msg, DST, len_in_bytes, k, hash);
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}
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else if (expand === '_internal_pass') {
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// for internal tests only
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prb = msg;
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}
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else {
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throw new Error('expand must be "xmd" or "xof"');
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}
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const u = new Array(count);
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for (let i = 0; i < count; i++) {
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const e = new Array(m);
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for (let j = 0; j < m; j++) {
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const elm_offset = L * (j + i * m);
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const tv = prb.subarray(elm_offset, elm_offset + L);
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e[j] = (0, modular_js_1.mod)(os2ip(tv), p);
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}
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u[i] = e;
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}
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return u;
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}
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function isogenyMap(field, map) {
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// Make same order as in spec
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const COEFF = map.map((i) => Array.from(i).reverse());
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return (x, y) => {
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const [xNum, xDen, yNum, yDen] = COEFF.map((val) => val.reduce((acc, i) => field.add(field.mul(acc, x), i)));
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x = field.div(xNum, xDen); // xNum / xDen
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y = field.mul(y, field.div(yNum, yDen)); // y * (yNum / yDev)
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return { x, y };
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};
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}
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function createHasher(Point, mapToCurve, def) {
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if (typeof mapToCurve !== 'function')
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throw new Error('mapToCurve() must be defined');
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return {
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// Encodes byte string to elliptic curve.
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// hash_to_curve from https://www.rfc-editor.org/rfc/rfc9380#section-3
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hashToCurve(msg, options) {
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const u = hash_to_field(msg, 2, { ...def, DST: def.DST, ...options });
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const u0 = Point.fromAffine(mapToCurve(u[0]));
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const u1 = Point.fromAffine(mapToCurve(u[1]));
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const P = u0.add(u1).clearCofactor();
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P.assertValidity();
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return P;
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},
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// Encodes byte string to elliptic curve.
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// encode_to_curve from https://www.rfc-editor.org/rfc/rfc9380#section-3
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encodeToCurve(msg, options) {
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const u = hash_to_field(msg, 1, { ...def, DST: def.encodeDST, ...options });
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const P = Point.fromAffine(mapToCurve(u[0])).clearCofactor();
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P.assertValidity();
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return P;
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},
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// Same as encodeToCurve, but without hash
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mapToCurve(scalars) {
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if (!Array.isArray(scalars))
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throw new Error('mapToCurve: expected array of bigints');
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for (const i of scalars)
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if (typeof i !== 'bigint')
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throw new Error(`mapToCurve: expected array of bigints, got ${i} in array`);
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const P = Point.fromAffine(mapToCurve(scalars)).clearCofactor();
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P.assertValidity();
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return P;
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},
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};
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}
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//# sourceMappingURL=hash-to-curve.js.map
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