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- "use strict";
- Object.defineProperty(exports, "__esModule", { value: true });
- exports.isNegativeLE = void 0;
- exports.mod = mod;
- exports.pow = pow;
- exports.pow2 = pow2;
- exports.invert = invert;
- exports.tonelliShanks = tonelliShanks;
- exports.FpSqrt = FpSqrt;
- exports.validateField = validateField;
- exports.FpPow = FpPow;
- exports.FpInvertBatch = FpInvertBatch;
- exports.FpDiv = FpDiv;
- exports.FpIsSquare = FpIsSquare;
- exports.nLength = nLength;
- exports.Field = Field;
- exports.FpSqrtOdd = FpSqrtOdd;
- exports.FpSqrtEven = FpSqrtEven;
- exports.hashToPrivateScalar = hashToPrivateScalar;
- exports.getFieldBytesLength = getFieldBytesLength;
- exports.getMinHashLength = getMinHashLength;
- exports.mapHashToField = mapHashToField;
- /*! noble-curves - MIT License (c) 2022 Paul Miller (paulmillr.com) */
- // Utilities for modular arithmetics and finite fields
- const utils_js_1 = require("./utils.js");
- // prettier-ignore
- const _0n = BigInt(0), _1n = BigInt(1), _2n = BigInt(2), _3n = BigInt(3);
- // prettier-ignore
- const _4n = BigInt(4), _5n = BigInt(5), _8n = BigInt(8);
- // prettier-ignore
- const _9n = BigInt(9), _16n = BigInt(16);
- // Calculates a modulo b
- function mod(a, b) {
- const result = a % b;
- return result >= _0n ? result : b + result;
- }
- /**
- * Efficiently raise num to power and do modular division.
- * Unsafe in some contexts: uses ladder, so can expose bigint bits.
- * @example
- * pow(2n, 6n, 11n) // 64n % 11n == 9n
- */
- // TODO: use field version && remove
- function pow(num, power, modulo) {
- if (modulo <= _0n || power < _0n)
- throw new Error('Expected power/modulo > 0');
- if (modulo === _1n)
- return _0n;
- let res = _1n;
- while (power > _0n) {
- if (power & _1n)
- res = (res * num) % modulo;
- num = (num * num) % modulo;
- power >>= _1n;
- }
- return res;
- }
- // Does x ^ (2 ^ power) mod p. pow2(30, 4) == 30 ^ (2 ^ 4)
- function pow2(x, power, modulo) {
- let res = x;
- while (power-- > _0n) {
- res *= res;
- res %= modulo;
- }
- return res;
- }
- // Inverses number over modulo
- function invert(number, modulo) {
- if (number === _0n || modulo <= _0n) {
- throw new Error(`invert: expected positive integers, got n=${number} mod=${modulo}`);
- }
- // Euclidean GCD https://brilliant.org/wiki/extended-euclidean-algorithm/
- // Fermat's little theorem "CT-like" version inv(n) = n^(m-2) mod m is 30x slower.
- let a = mod(number, modulo);
- let b = modulo;
- // prettier-ignore
- let x = _0n, y = _1n, u = _1n, v = _0n;
- while (a !== _0n) {
- // JIT applies optimization if those two lines follow each other
- const q = b / a;
- const r = b % a;
- const m = x - u * q;
- const n = y - v * q;
- // prettier-ignore
- b = a, a = r, x = u, y = v, u = m, v = n;
- }
- const gcd = b;
- if (gcd !== _1n)
- throw new Error('invert: does not exist');
- return mod(x, modulo);
- }
- /**
- * Tonelli-Shanks square root search algorithm.
- * 1. https://eprint.iacr.org/2012/685.pdf (page 12)
- * 2. Square Roots from 1; 24, 51, 10 to Dan Shanks
- * Will start an infinite loop if field order P is not prime.
- * @param P field order
- * @returns function that takes field Fp (created from P) and number n
- */
- function tonelliShanks(P) {
- // Legendre constant: used to calculate Legendre symbol (a | p),
- // which denotes the value of a^((p-1)/2) (mod p).
- // (a | p) ≡ 1 if a is a square (mod p)
- // (a | p) ≡ -1 if a is not a square (mod p)
- // (a | p) ≡ 0 if a ≡ 0 (mod p)
- const legendreC = (P - _1n) / _2n;
- let Q, S, Z;
- // Step 1: By factoring out powers of 2 from p - 1,
- // find q and s such that p - 1 = q*(2^s) with q odd
- for (Q = P - _1n, S = 0; Q % _2n === _0n; Q /= _2n, S++)
- ;
- // Step 2: Select a non-square z such that (z | p) ≡ -1 and set c ≡ zq
- for (Z = _2n; Z < P && pow(Z, legendreC, P) !== P - _1n; Z++)
- ;
- // Fast-path
- if (S === 1) {
- const p1div4 = (P + _1n) / _4n;
- return function tonelliFast(Fp, n) {
- const root = Fp.pow(n, p1div4);
- if (!Fp.eql(Fp.sqr(root), n))
- throw new Error('Cannot find square root');
- return root;
- };
- }
- // Slow-path
- const Q1div2 = (Q + _1n) / _2n;
- return function tonelliSlow(Fp, n) {
- // Step 0: Check that n is indeed a square: (n | p) should not be ≡ -1
- if (Fp.pow(n, legendreC) === Fp.neg(Fp.ONE))
- throw new Error('Cannot find square root');
- let r = S;
- // TODO: will fail at Fp2/etc
- let g = Fp.pow(Fp.mul(Fp.ONE, Z), Q); // will update both x and b
- let x = Fp.pow(n, Q1div2); // first guess at the square root
- let b = Fp.pow(n, Q); // first guess at the fudge factor
- while (!Fp.eql(b, Fp.ONE)) {
- if (Fp.eql(b, Fp.ZERO))
- return Fp.ZERO; // https://en.wikipedia.org/wiki/Tonelli%E2%80%93Shanks_algorithm (4. If t = 0, return r = 0)
- // Find m such b^(2^m)==1
- let m = 1;
- for (let t2 = Fp.sqr(b); m < r; m++) {
- if (Fp.eql(t2, Fp.ONE))
- break;
- t2 = Fp.sqr(t2); // t2 *= t2
- }
- // NOTE: r-m-1 can be bigger than 32, need to convert to bigint before shift, otherwise there will be overflow
- const ge = Fp.pow(g, _1n << BigInt(r - m - 1)); // ge = 2^(r-m-1)
- g = Fp.sqr(ge); // g = ge * ge
- x = Fp.mul(x, ge); // x *= ge
- b = Fp.mul(b, g); // b *= g
- r = m;
- }
- return x;
- };
- }
- function FpSqrt(P) {
- // NOTE: different algorithms can give different roots, it is up to user to decide which one they want.
- // For example there is FpSqrtOdd/FpSqrtEven to choice root based on oddness (used for hash-to-curve).
- // P ≡ 3 (mod 4)
- // √n = n^((P+1)/4)
- if (P % _4n === _3n) {
- // Not all roots possible!
- // const ORDER =
- // 0x1a0111ea397fe69a4b1ba7b6434bacd764774b84f38512bf6730d2a0f6b0f6241eabfffeb153ffffb9feffffffffaaabn;
- // const NUM = 72057594037927816n;
- const p1div4 = (P + _1n) / _4n;
- return function sqrt3mod4(Fp, n) {
- const root = Fp.pow(n, p1div4);
- // Throw if root**2 != n
- if (!Fp.eql(Fp.sqr(root), n))
- throw new Error('Cannot find square root');
- return root;
- };
- }
- // Atkin algorithm for q ≡ 5 (mod 8), https://eprint.iacr.org/2012/685.pdf (page 10)
- if (P % _8n === _5n) {
- const c1 = (P - _5n) / _8n;
- return function sqrt5mod8(Fp, n) {
- const n2 = Fp.mul(n, _2n);
- const v = Fp.pow(n2, c1);
- const nv = Fp.mul(n, v);
- const i = Fp.mul(Fp.mul(nv, _2n), v);
- const root = Fp.mul(nv, Fp.sub(i, Fp.ONE));
- if (!Fp.eql(Fp.sqr(root), n))
- throw new Error('Cannot find square root');
- return root;
- };
- }
- // P ≡ 9 (mod 16)
- if (P % _16n === _9n) {
- // NOTE: tonelli is too slow for bls-Fp2 calculations even on start
- // Means we cannot use sqrt for constants at all!
- //
- // const c1 = Fp.sqrt(Fp.negate(Fp.ONE)); // 1. c1 = sqrt(-1) in F, i.e., (c1^2) == -1 in F
- // const c2 = Fp.sqrt(c1); // 2. c2 = sqrt(c1) in F, i.e., (c2^2) == c1 in F
- // const c3 = Fp.sqrt(Fp.negate(c1)); // 3. c3 = sqrt(-c1) in F, i.e., (c3^2) == -c1 in F
- // const c4 = (P + _7n) / _16n; // 4. c4 = (q + 7) / 16 # Integer arithmetic
- // sqrt = (x) => {
- // let tv1 = Fp.pow(x, c4); // 1. tv1 = x^c4
- // let tv2 = Fp.mul(c1, tv1); // 2. tv2 = c1 * tv1
- // const tv3 = Fp.mul(c2, tv1); // 3. tv3 = c2 * tv1
- // let tv4 = Fp.mul(c3, tv1); // 4. tv4 = c3 * tv1
- // const e1 = Fp.equals(Fp.square(tv2), x); // 5. e1 = (tv2^2) == x
- // const e2 = Fp.equals(Fp.square(tv3), x); // 6. e2 = (tv3^2) == x
- // tv1 = Fp.cmov(tv1, tv2, e1); // 7. tv1 = CMOV(tv1, tv2, e1) # Select tv2 if (tv2^2) == x
- // tv2 = Fp.cmov(tv4, tv3, e2); // 8. tv2 = CMOV(tv4, tv3, e2) # Select tv3 if (tv3^2) == x
- // const e3 = Fp.equals(Fp.square(tv2), x); // 9. e3 = (tv2^2) == x
- // return Fp.cmov(tv1, tv2, e3); // 10. z = CMOV(tv1, tv2, e3) # Select the sqrt from tv1 and tv2
- // }
- }
- // Other cases: Tonelli-Shanks algorithm
- return tonelliShanks(P);
- }
- // Little-endian check for first LE bit (last BE bit);
- const isNegativeLE = (num, modulo) => (mod(num, modulo) & _1n) === _1n;
- exports.isNegativeLE = isNegativeLE;
- // prettier-ignore
- const FIELD_FIELDS = [
- 'create', 'isValid', 'is0', 'neg', 'inv', 'sqrt', 'sqr',
- 'eql', 'add', 'sub', 'mul', 'pow', 'div',
- 'addN', 'subN', 'mulN', 'sqrN'
- ];
- function validateField(field) {
- const initial = {
- ORDER: 'bigint',
- MASK: 'bigint',
- BYTES: 'isSafeInteger',
- BITS: 'isSafeInteger',
- };
- const opts = FIELD_FIELDS.reduce((map, val) => {
- map[val] = 'function';
- return map;
- }, initial);
- return (0, utils_js_1.validateObject)(field, opts);
- }
- // Generic field functions
- /**
- * Same as `pow` but for Fp: non-constant-time.
- * Unsafe in some contexts: uses ladder, so can expose bigint bits.
- */
- function FpPow(f, num, power) {
- // Should have same speed as pow for bigints
- // TODO: benchmark!
- if (power < _0n)
- throw new Error('Expected power > 0');
- if (power === _0n)
- return f.ONE;
- if (power === _1n)
- return num;
- let p = f.ONE;
- let d = num;
- while (power > _0n) {
- if (power & _1n)
- p = f.mul(p, d);
- d = f.sqr(d);
- power >>= _1n;
- }
- return p;
- }
- /**
- * Efficiently invert an array of Field elements.
- * `inv(0)` will return `undefined` here: make sure to throw an error.
- */
- function FpInvertBatch(f, nums) {
- const tmp = new Array(nums.length);
- // Walk from first to last, multiply them by each other MOD p
- const lastMultiplied = nums.reduce((acc, num, i) => {
- if (f.is0(num))
- return acc;
- tmp[i] = acc;
- return f.mul(acc, num);
- }, f.ONE);
- // Invert last element
- const inverted = f.inv(lastMultiplied);
- // Walk from last to first, multiply them by inverted each other MOD p
- nums.reduceRight((acc, num, i) => {
- if (f.is0(num))
- return acc;
- tmp[i] = f.mul(acc, tmp[i]);
- return f.mul(acc, num);
- }, inverted);
- return tmp;
- }
- function FpDiv(f, lhs, rhs) {
- return f.mul(lhs, typeof rhs === 'bigint' ? invert(rhs, f.ORDER) : f.inv(rhs));
- }
- // This function returns True whenever the value x is a square in the field F.
- function FpIsSquare(f) {
- const legendreConst = (f.ORDER - _1n) / _2n; // Integer arithmetic
- return (x) => {
- const p = f.pow(x, legendreConst);
- return f.eql(p, f.ZERO) || f.eql(p, f.ONE);
- };
- }
- // CURVE.n lengths
- function nLength(n, nBitLength) {
- // Bit size, byte size of CURVE.n
- const _nBitLength = nBitLength !== undefined ? nBitLength : n.toString(2).length;
- const nByteLength = Math.ceil(_nBitLength / 8);
- return { nBitLength: _nBitLength, nByteLength };
- }
- /**
- * Initializes a finite field over prime. **Non-primes are not supported.**
- * Do not init in loop: slow. Very fragile: always run a benchmark on a change.
- * Major performance optimizations:
- * * a) denormalized operations like mulN instead of mul
- * * b) same object shape: never add or remove keys
- * * c) Object.freeze
- * @param ORDER prime positive bigint
- * @param bitLen how many bits the field consumes
- * @param isLE (def: false) if encoding / decoding should be in little-endian
- * @param redef optional faster redefinitions of sqrt and other methods
- */
- function Field(ORDER, bitLen, isLE = false, redef = {}) {
- if (ORDER <= _0n)
- throw new Error(`Expected Field ORDER > 0, got ${ORDER}`);
- const { nBitLength: BITS, nByteLength: BYTES } = nLength(ORDER, bitLen);
- if (BYTES > 2048)
- throw new Error('Field lengths over 2048 bytes are not supported');
- const sqrtP = FpSqrt(ORDER);
- const f = Object.freeze({
- ORDER,
- BITS,
- BYTES,
- MASK: (0, utils_js_1.bitMask)(BITS),
- ZERO: _0n,
- ONE: _1n,
- create: (num) => mod(num, ORDER),
- isValid: (num) => {
- if (typeof num !== 'bigint')
- throw new Error(`Invalid field element: expected bigint, got ${typeof num}`);
- return _0n <= num && num < ORDER; // 0 is valid element, but it's not invertible
- },
- is0: (num) => num === _0n,
- isOdd: (num) => (num & _1n) === _1n,
- neg: (num) => mod(-num, ORDER),
- eql: (lhs, rhs) => lhs === rhs,
- sqr: (num) => mod(num * num, ORDER),
- add: (lhs, rhs) => mod(lhs + rhs, ORDER),
- sub: (lhs, rhs) => mod(lhs - rhs, ORDER),
- mul: (lhs, rhs) => mod(lhs * rhs, ORDER),
- pow: (num, power) => FpPow(f, num, power),
- div: (lhs, rhs) => mod(lhs * invert(rhs, ORDER), ORDER),
- // Same as above, but doesn't normalize
- sqrN: (num) => num * num,
- addN: (lhs, rhs) => lhs + rhs,
- subN: (lhs, rhs) => lhs - rhs,
- mulN: (lhs, rhs) => lhs * rhs,
- inv: (num) => invert(num, ORDER),
- sqrt: redef.sqrt || ((n) => sqrtP(f, n)),
- invertBatch: (lst) => FpInvertBatch(f, lst),
- // TODO: do we really need constant cmov?
- // We don't have const-time bigints anyway, so probably will be not very useful
- cmov: (a, b, c) => (c ? b : a),
- toBytes: (num) => (isLE ? (0, utils_js_1.numberToBytesLE)(num, BYTES) : (0, utils_js_1.numberToBytesBE)(num, BYTES)),
- fromBytes: (bytes) => {
- if (bytes.length !== BYTES)
- throw new Error(`Fp.fromBytes: expected ${BYTES}, got ${bytes.length}`);
- return isLE ? (0, utils_js_1.bytesToNumberLE)(bytes) : (0, utils_js_1.bytesToNumberBE)(bytes);
- },
- });
- return Object.freeze(f);
- }
- function FpSqrtOdd(Fp, elm) {
- if (!Fp.isOdd)
- throw new Error(`Field doesn't have isOdd`);
- const root = Fp.sqrt(elm);
- return Fp.isOdd(root) ? root : Fp.neg(root);
- }
- function FpSqrtEven(Fp, elm) {
- if (!Fp.isOdd)
- throw new Error(`Field doesn't have isOdd`);
- const root = Fp.sqrt(elm);
- return Fp.isOdd(root) ? Fp.neg(root) : root;
- }
- /**
- * "Constant-time" private key generation utility.
- * Same as mapKeyToField, but accepts less bytes (40 instead of 48 for 32-byte field).
- * Which makes it slightly more biased, less secure.
- * @deprecated use mapKeyToField instead
- */
- function hashToPrivateScalar(hash, groupOrder, isLE = false) {
- hash = (0, utils_js_1.ensureBytes)('privateHash', hash);
- const hashLen = hash.length;
- const minLen = nLength(groupOrder).nByteLength + 8;
- if (minLen < 24 || hashLen < minLen || hashLen > 1024)
- throw new Error(`hashToPrivateScalar: expected ${minLen}-1024 bytes of input, got ${hashLen}`);
- const num = isLE ? (0, utils_js_1.bytesToNumberLE)(hash) : (0, utils_js_1.bytesToNumberBE)(hash);
- return mod(num, groupOrder - _1n) + _1n;
- }
- /**
- * Returns total number of bytes consumed by the field element.
- * For example, 32 bytes for usual 256-bit weierstrass curve.
- * @param fieldOrder number of field elements, usually CURVE.n
- * @returns byte length of field
- */
- function getFieldBytesLength(fieldOrder) {
- if (typeof fieldOrder !== 'bigint')
- throw new Error('field order must be bigint');
- const bitLength = fieldOrder.toString(2).length;
- return Math.ceil(bitLength / 8);
- }
- /**
- * Returns minimal amount of bytes that can be safely reduced
- * by field order.
- * Should be 2^-128 for 128-bit curve such as P256.
- * @param fieldOrder number of field elements, usually CURVE.n
- * @returns byte length of target hash
- */
- function getMinHashLength(fieldOrder) {
- const length = getFieldBytesLength(fieldOrder);
- return length + Math.ceil(length / 2);
- }
- /**
- * "Constant-time" private key generation utility.
- * Can take (n + n/2) or more bytes of uniform input e.g. from CSPRNG or KDF
- * and convert them into private scalar, with the modulo bias being negligible.
- * Needs at least 48 bytes of input for 32-byte private key.
- * https://research.kudelskisecurity.com/2020/07/28/the-definitive-guide-to-modulo-bias-and-how-to-avoid-it/
- * FIPS 186-5, A.2 https://csrc.nist.gov/publications/detail/fips/186/5/final
- * RFC 9380, https://www.rfc-editor.org/rfc/rfc9380#section-5
- * @param hash hash output from SHA3 or a similar function
- * @param groupOrder size of subgroup - (e.g. secp256k1.CURVE.n)
- * @param isLE interpret hash bytes as LE num
- * @returns valid private scalar
- */
- function mapHashToField(key, fieldOrder, isLE = false) {
- const len = key.length;
- const fieldLen = getFieldBytesLength(fieldOrder);
- const minLen = getMinHashLength(fieldOrder);
- // No small numbers: need to understand bias story. No huge numbers: easier to detect JS timings.
- if (len < 16 || len < minLen || len > 1024)
- throw new Error(`expected ${minLen}-1024 bytes of input, got ${len}`);
- const num = isLE ? (0, utils_js_1.bytesToNumberBE)(key) : (0, utils_js_1.bytesToNumberLE)(key);
- // `mod(x, 11)` can sometimes produce 0. `mod(x, 10) + 1` is the same, but no 0
- const reduced = mod(num, fieldOrder - _1n) + _1n;
- return isLE ? (0, utils_js_1.numberToBytesLE)(reduced, fieldLen) : (0, utils_js_1.numberToBytesBE)(reduced, fieldLen);
- }
- //# sourceMappingURL=modular.js.map
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