newsroom/node_modules/@noble/curves/abstract/modular.js

"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.FpLegendre = FpLegendre;
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;
/**
 * Utils for modular division and fields.
 * Field over 11 is a finite (Galois) field is integer number operations `mod 11`.
 * There is no division: it is replaced by modular multiplicative inverse.
 * @module
 */
/*! noble-curves - MIT License (c) 2022 Paul Miller (paulmillr.com) */
const utils_ts_1 = require("../utils.js");
// prettier-ignore
const _0n = BigInt(0), _1n = BigInt(1), _2n = /* @__PURE__ */ BigInt(2), _3n = /* @__PURE__ */ BigInt(3);
// prettier-ignore
const _4n = /* @__PURE__ */ BigInt(4), _5n = /* @__PURE__ */ BigInt(5), _7n = /* @__PURE__ */ BigInt(7);
// prettier-ignore
const _8n = /* @__PURE__ */ BigInt(8), _9n = /* @__PURE__ */ BigInt(9), _16n = /* @__PURE__ */ 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
 */
function pow(num, power, modulo) {
    return FpPow(Field(modulo), num, power);
}
/** 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.
 * Implemented using [Euclidean GCD](https://brilliant.org/wiki/extended-euclidean-algorithm/).
 */
function invert(number, modulo) {
    if (number === _0n)
        throw new Error('invert: expected non-zero number');
    if (modulo <= _0n)
        throw new Error('invert: expected positive modulus, got ' + modulo);
    // 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);
}
function assertIsSquare(Fp, root, n) {
    if (!Fp.eql(Fp.sqr(root), n))
        throw new Error('Cannot find square root');
}
// Not all roots are possible! Example which will throw:
// const NUM =
// n = 72057594037927816n;
// Fp = Field(BigInt('0x1a0111ea397fe69a4b1ba7b6434bacd764774b84f38512bf6730d2a0f6b0f6241eabfffeb153ffffb9feffffffffaaab'));
function sqrt3mod4(Fp, n) {
    const p1div4 = (Fp.ORDER + _1n) / _4n;
    const root = Fp.pow(n, p1div4);
    assertIsSquare(Fp, root, n);
    return root;
}
function sqrt5mod8(Fp, n) {
    const p5div8 = (Fp.ORDER - _5n) / _8n;
    const n2 = Fp.mul(n, _2n);
    const v = Fp.pow(n2, p5div8);
    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));
    assertIsSquare(Fp, root, n);
    return root;
}
// Based on RFC9380, Kong algorithm
// prettier-ignore
function sqrt9mod16(P) {
    const Fp_ = Field(P);
    const tn = tonelliShanks(P);
    const c1 = tn(Fp_, Fp_.neg(Fp_.ONE)); //  1. c1 = sqrt(-1) in F, i.e., (c1^2) == -1 in F
    const c2 = tn(Fp_, c1); //  2. c2 = sqrt(c1) in F, i.e., (c2^2) == c1 in F
    const c3 = tn(Fp_, Fp_.neg(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
    return (Fp, n) => {
        let tv1 = Fp.pow(n, c4); //  1. tv1 = x^c4
        let tv2 = Fp.mul(tv1, c1); //  2. tv2 = c1 * tv1
        const tv3 = Fp.mul(tv1, c2); //  3. tv3 = c2 * tv1
        const tv4 = Fp.mul(tv1, c3); //  4. tv4 = c3 * tv1
        const e1 = Fp.eql(Fp.sqr(tv2), n); //  5.  e1 = (tv2^2) == x
        const e2 = Fp.eql(Fp.sqr(tv3), n); //  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.eql(Fp.sqr(tv2), n); //  9.  e3 = (tv2^2) == x
        const root = Fp.cmov(tv1, tv2, e3); // 10.  z = CMOV(tv1, tv2, e3)   # Select sqrt from tv1 & tv2
        assertIsSquare(Fp, root, n);
        return root;
    };
}
/**
 * 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
 * @param P field order
 * @returns function that takes field Fp (created from P) and number n
 */
function tonelliShanks(P) {
    // Initialization (precomputation).
    // Caching initialization could boost perf by 7%.
    if (P < _3n)
        throw new Error('sqrt is not defined for small field');
    // Factor P - 1 = Q * 2^S, where Q is odd
    let Q = P - _1n;
    let S = 0;
    while (Q % _2n === _0n) {
        Q /= _2n;
        S++;
    }
    // Find the first quadratic non-residue Z >= 2
    let Z = _2n;
    const _Fp = Field(P);
    while (FpLegendre(_Fp, Z) === 1) {
        // Basic primality test for P. After x iterations, chance of
        // not finding quadratic non-residue is 2^x, so 2^1000.
        if (Z++ > 1000)
            throw new Error('Cannot find square root: probably non-prime P');
    }
    // Fast-path; usually done before Z, but we do "primality test".
    if (S === 1)
        return sqrt3mod4;
    // Slow-path
    // TODO: test on Fp2 and others
    let cc = _Fp.pow(Z, Q); // c = z^Q
    const Q1div2 = (Q + _1n) / _2n;
    return function tonelliSlow(Fp, n) {
        if (Fp.is0(n))
            return n;
        // Check if n is a quadratic residue using Legendre symbol
        if (FpLegendre(Fp, n) !== 1)
            throw new Error('Cannot find square root');
        // Initialize variables for the main loop
        let M = S;
        let c = Fp.mul(Fp.ONE, cc); // c = z^Q, move cc from field _Fp into field Fp
        let t = Fp.pow(n, Q); // t = n^Q, first guess at the fudge factor
        let R = Fp.pow(n, Q1div2); // R = n^((Q+1)/2), first guess at the square root
        // Main loop
        // while t != 1
        while (!Fp.eql(t, Fp.ONE)) {
            if (Fp.is0(t))
                return Fp.ZERO; // if t=0 return R=0
            let i = 1;
            // Find the smallest i >= 1 such that t^(2^i) ≡ 1 (mod P)
            let t_tmp = Fp.sqr(t); // t^(2^1)
            while (!Fp.eql(t_tmp, Fp.ONE)) {
                i++;
                t_tmp = Fp.sqr(t_tmp); // t^(2^2)...
                if (i === M)
                    throw new Error('Cannot find square root');
            }
            // Calculate the exponent for b: 2^(M - i - 1)
            const exponent = _1n << BigInt(M - i - 1); // bigint is important
            const b = Fp.pow(c, exponent); // b = 2^(M - i - 1)
            // Update variables
            M = i;
            c = Fp.sqr(b); // c = b^2
            t = Fp.mul(t, c); // t = (t * b^2)
            R = Fp.mul(R, b); // R = R*b
        }
        return R;
    };
}
/**
 * Square root for a finite field. Will try optimized versions first:
 *
 * 1. P ≡ 3 (mod 4)
 * 2. P ≡ 5 (mod 8)
 * 3. P ≡ 9 (mod 16)
 * 4. Tonelli-Shanks algorithm
 *
 * 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).
 */
function FpSqrt(P) {
    // P ≡ 3 (mod 4) => √n = n^((P+1)/4)
    if (P % _4n === _3n)
        return sqrt3mod4;
    // P ≡ 5 (mod 8) => Atkin algorithm, page 10 of https://eprint.iacr.org/2012/685.pdf
    if (P % _8n === _5n)
        return sqrt5mod8;
    // P ≡ 9 (mod 16) => Kong algorithm, page 11 of https://eprint.iacr.org/2012/685.pdf (algorithm 4)
    if (P % _16n === _9n)
        return sqrt9mod16(P);
    // 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: 'number',
        BITS: 'number',
    };
    const opts = FIELD_FIELDS.reduce((map, val) => {
        map[val] = 'function';
        return map;
    }, initial);
    (0, utils_ts_1._validateObject)(field, opts);
    // const max = 16384;
    // if (field.BYTES < 1 || field.BYTES > max) throw new Error('invalid field');
    // if (field.BITS < 1 || field.BITS > 8 * max) throw new Error('invalid field');
    return field;
}
// 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(Fp, num, power) {
    if (power < _0n)
        throw new Error('invalid exponent, negatives unsupported');
    if (power === _0n)
        return Fp.ONE;
    if (power === _1n)
        return num;
    let p = Fp.ONE;
    let d = num;
    while (power > _0n) {
        if (power & _1n)
            p = Fp.mul(p, d);
        d = Fp.sqr(d);
        power >>= _1n;
    }
    return p;
}
/**
 * Efficiently invert an array of Field elements.
 * Exception-free. Will return `undefined` for 0 elements.
 * @param passZero map 0 to 0 (instead of undefined)
 */
function FpInvertBatch(Fp, nums, passZero = false) {
    const inverted = new Array(nums.length).fill(passZero ? Fp.ZERO : undefined);
    // Walk from first to last, multiply them by each other MOD p
    const multipliedAcc = nums.reduce((acc, num, i) => {
        if (Fp.is0(num))
            return acc;
        inverted[i] = acc;
        return Fp.mul(acc, num);
    }, Fp.ONE);
    // Invert last element
    const invertedAcc = Fp.inv(multipliedAcc);
    // Walk from last to first, multiply them by inverted each other MOD p
    nums.reduceRight((acc, num, i) => {
        if (Fp.is0(num))
            return acc;
        inverted[i] = Fp.mul(acc, inverted[i]);
        return Fp.mul(acc, num);
    }, invertedAcc);
    return inverted;
}
// TODO: remove
function FpDiv(Fp, lhs, rhs) {
    return Fp.mul(lhs, typeof rhs === 'bigint' ? invert(rhs, Fp.ORDER) : Fp.inv(rhs));
}
/**
 * Legendre symbol.
 * Legendre constant is 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), quadratic residue
 * * (a | p) ≡ -1   if a is not a square (mod p), quadratic non residue
 * * (a | p) ≡ 0    if a ≡ 0 (mod p)
 */
function FpLegendre(Fp, n) {
    // We can use 3rd argument as optional cache of this value
    // but seems unneeded for now. The operation is very fast.
    const p1mod2 = (Fp.ORDER - _1n) / _2n;
    const powered = Fp.pow(n, p1mod2);
    const yes = Fp.eql(powered, Fp.ONE);
    const zero = Fp.eql(powered, Fp.ZERO);
    const no = Fp.eql(powered, Fp.neg(Fp.ONE));
    if (!yes && !zero && !no)
        throw new Error('invalid Legendre symbol result');
    return yes ? 1 : zero ? 0 : -1;
}
// This function returns True whenever the value x is a square in the field F.
function FpIsSquare(Fp, n) {
    const l = FpLegendre(Fp, n);
    return l === 1;
}
// CURVE.n lengths
function nLength(n, nBitLength) {
    // Bit size, byte size of CURVE.n
    if (nBitLength !== undefined)
        (0, utils_ts_1.anumber)(nBitLength);
    const _nBitLength = nBitLength !== undefined ? nBitLength : n.toString(2).length;
    const nByteLength = Math.ceil(_nBitLength / 8);
    return { nBitLength: _nBitLength, nByteLength };
}
/**
 * Creates a finite field. Major performance optimizations:
 * * 1. Denormalized operations like mulN instead of mul.
 * * 2. Identical object shape: never add or remove keys.
 * * 3. `Object.freeze`.
 * Fragile: always run a benchmark on a change.
 * Security note: operations don't check 'isValid' for all elements for performance reasons,
 * it is caller responsibility to check this.
 * This is low-level code, please make sure you know what you're doing.
 *
 * Note about field properties:
 * * CHARACTERISTIC p = prime number, number of elements in main subgroup.
 * * ORDER q = similar to cofactor in curves, may be composite `q = p^m`.
 *
 * @param ORDER field order, probably prime, or could be composite
 * @param bitLen how many bits the field consumes
 * @param isLE (default: false) if encoding / decoding should be in little-endian
 * @param redef optional faster redefinitions of sqrt and other methods
 */
function Field(ORDER, bitLenOrOpts, // TODO: use opts only in v2?
isLE = false, opts = {}) {
    if (ORDER <= _0n)
        throw new Error('invalid field: expected ORDER > 0, got ' + ORDER);
    let _nbitLength = undefined;
    let _sqrt = undefined;
    let modFromBytes = false;
    let allowedLengths = undefined;
    if (typeof bitLenOrOpts === 'object' && bitLenOrOpts != null) {
        if (opts.sqrt || isLE)
            throw new Error('cannot specify opts in two arguments');
        const _opts = bitLenOrOpts;
        if (_opts.BITS)
            _nbitLength = _opts.BITS;
        if (_opts.sqrt)
            _sqrt = _opts.sqrt;
        if (typeof _opts.isLE === 'boolean')
            isLE = _opts.isLE;
        if (typeof _opts.modFromBytes === 'boolean')
            modFromBytes = _opts.modFromBytes;
        allowedLengths = _opts.allowedLengths;
    }
    else {
        if (typeof bitLenOrOpts === 'number')
            _nbitLength = bitLenOrOpts;
        if (opts.sqrt)
            _sqrt = opts.sqrt;
    }
    const { nBitLength: BITS, nByteLength: BYTES } = nLength(ORDER, _nbitLength);
    if (BYTES > 2048)
        throw new Error('invalid field: expected ORDER of <= 2048 bytes');
    let sqrtP; // cached sqrtP
    const f = Object.freeze({
        ORDER,
        isLE,
        BITS,
        BYTES,
        MASK: (0, utils_ts_1.bitMask)(BITS),
        ZERO: _0n,
        ONE: _1n,
        allowedLengths: allowedLengths,
        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,
        // is valid and invertible
        isValidNot0: (num) => !f.is0(num) && f.isValid(num),
        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: _sqrt ||
            ((n) => {
                if (!sqrtP)
                    sqrtP = FpSqrt(ORDER);
                return sqrtP(f, n);
            }),
        toBytes: (num) => (isLE ? (0, utils_ts_1.numberToBytesLE)(num, BYTES) : (0, utils_ts_1.numberToBytesBE)(num, BYTES)),
        fromBytes: (bytes, skipValidation = true) => {
            if (allowedLengths) {
                if (!allowedLengths.includes(bytes.length) || bytes.length > BYTES) {
                    throw new Error('Field.fromBytes: expected ' + allowedLengths + ' bytes, got ' + bytes.length);
                }
                const padded = new Uint8Array(BYTES);
                // isLE add 0 to right, !isLE to the left.
                padded.set(bytes, isLE ? 0 : padded.length - bytes.length);
                bytes = padded;
            }
            if (bytes.length !== BYTES)
                throw new Error('Field.fromBytes: expected ' + BYTES + ' bytes, got ' + bytes.length);
            let scalar = isLE ? (0, utils_ts_1.bytesToNumberLE)(bytes) : (0, utils_ts_1.bytesToNumberBE)(bytes);
            if (modFromBytes)
                scalar = mod(scalar, ORDER);
            if (!skipValidation)
                if (!f.isValid(scalar))
                    throw new Error('invalid field element: outside of range 0..ORDER');
            // NOTE: we don't validate scalar here, please use isValid. This done such way because some
            // protocol may allow non-reduced scalar that reduced later or changed some other way.
            return scalar;
        },
        // TODO: we don't need it here, move out to separate fn
        invertBatch: (lst) => FpInvertBatch(f, lst),
        // We can't move this out because Fp6, Fp12 implement it
        // and it's unclear what to return in there.
        cmov: (a, b, c) => (c ? b : a),
    });
    return Object.freeze(f);
}
// Generic random scalar, we can do same for other fields if via Fp2.mul(Fp2.ONE, Fp2.random)?
// This allows unsafe methods like ignore bias or zero. These unsafe, but often used in different protocols (if deterministic RNG).
// which mean we cannot force this via opts.
// Not sure what to do with randomBytes, we can accept it inside opts if wanted.
// Probably need to export getMinHashLength somewhere?
// random(bytes?: Uint8Array, unsafeAllowZero = false, unsafeAllowBias = false) {
//   const LEN = !unsafeAllowBias ? getMinHashLength(ORDER) : BYTES;
//   if (bytes === undefined) bytes = randomBytes(LEN); // _opts.randomBytes?
//   const num = isLE ? bytesToNumberLE(bytes) : bytesToNumberBE(bytes);
//   // `mod(x, 11)` can sometimes produce 0. `mod(x, 10) + 1` is the same, but no 0
//   const reduced = unsafeAllowZero ? mod(num, ORDER) : mod(num, ORDER - _1n) + _1n;
//   return reduced;
// },
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_ts_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_ts_1.bytesToNumberLE)(hash) : (0, utils_ts_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_ts_1.bytesToNumberLE)(key) : (0, utils_ts_1.bytesToNumberBE)(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_ts_1.numberToBytesLE)(reduced, fieldLen) : (0, utils_ts_1.numberToBytesBE)(reduced, fieldLen);
}
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