463 lines
18 KiB
JavaScript
463 lines
18 KiB
JavaScript
/**
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* Implements [Poseidon](https://www.poseidon-hash.info) ZK-friendly hash.
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*
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* There are many poseidon variants with different constants.
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* We don't provide them: you should construct them manually.
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* Check out [micro-starknet](https://github.com/paulmillr/micro-starknet) package for a proper example.
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* @module
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*/
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/*! noble-curves - MIT License (c) 2022 Paul Miller (paulmillr.com) */
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import { asafenumber, bitGet, validateObject } from "../utils.js";
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import { FpInvertBatch, FpPow, validateField } from "./modular.js";
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// Grain LFSR (Linear-Feedback Shift Register): https://eprint.iacr.org/2009/109.pdf
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function grainLFSR(state) {
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// Advances the caller-provided 80-entry state array in place; only the length
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// is checked here, so entries are assumed to already be bits.
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let pos = 0;
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if (state.length !== 80)
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throw new Error('grainLFRS: wrong state length, should be 80 bits');
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const getBit = () => {
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const r = (offset) => state[(pos + offset) % 80];
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const bit = r(62) ^ r(51) ^ r(38) ^ r(23) ^ r(13) ^ r(0);
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state[pos] = bit;
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pos = ++pos % 80;
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return !!bit;
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};
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for (let i = 0; i < 160; i++)
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getBit();
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return () => {
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// https://en.wikipedia.org/wiki/Shrinking_generator
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while (true) {
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const b1 = getBit();
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const b2 = getBit();
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if (!b1)
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continue;
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return b2;
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}
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};
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}
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function assertValidPosOpts(opts) {
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const { Fp, roundsFull } = opts;
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validateField(Fp);
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validateObject(opts, {
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t: 'number',
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roundsFull: 'number',
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roundsPartial: 'number',
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}, {
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isSboxInverse: 'boolean',
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});
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for (const k of ['t', 'roundsFull', 'roundsPartial']) {
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asafenumber(opts[k], k);
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if (opts[k] < 1)
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throw new Error('invalid number ' + k);
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}
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// Poseidon splits full rounds as `R_F / 2`, then partial rounds, then `R_F / 2` again.
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if (roundsFull & 1)
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throw new Error('roundsFull is not even' + roundsFull);
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}
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function poseidonGrain(opts) {
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assertValidPosOpts(opts);
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const { Fp } = opts;
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const state = Array(80).fill(1);
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let pos = 0;
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const writeBits = (value, bitCount) => {
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for (let i = bitCount - 1; i >= 0; i--)
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state[pos++] = Number(bitGet(value, i));
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};
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const _0n = BigInt(0);
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const _1n = BigInt(1);
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// The Grain seed layout is fixed-width: `Fp.BITS` and `t` use 12 bits,
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// `roundsFull` and `roundsPartial` use 10, so larger values are truncated here.
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// This is intentional for compatibility with snarkVM / arkworks PoseidonGrainLFSR:
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// they write the same fixed-width seed fields without range checks, then still consume
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// the LFSR using the caller-provided round count for ARK/MDS generation.
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// Normalizing or rejecting here would diverge from those implementations.
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writeBits(_1n, 2); // prime field
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writeBits(opts.isSboxInverse ? _1n : _0n, 4); // b2..b5
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writeBits(BigInt(Fp.BITS), 12); // b6..b17
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writeBits(BigInt(opts.t), 12); // b18..b29
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writeBits(BigInt(opts.roundsFull), 10); // b30..b39
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writeBits(BigInt(opts.roundsPartial), 10); // b40..b49
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const getBit = grainLFSR(state);
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return (count, reject) => {
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const res = [];
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for (let i = 0; i < count; i++) {
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while (true) {
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let num = _0n;
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for (let i = 0; i < Fp.BITS; i++) {
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num <<= _1n;
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if (getBit())
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num |= _1n;
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}
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if (reject && num >= Fp.ORDER)
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continue; // rejection sampling
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res.push(Fp.create(num));
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break;
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}
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}
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return res;
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};
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}
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// NOTE: this is not standard but used often for constant generation for poseidon
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// (grain LFRS-like structure)
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/**
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* @param opts - Poseidon grain options. See {@link PoseidonGrainOpts}.
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* @param skipMDS - Number of MDS samples to skip.
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* @returns Generated constants.
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* @throws If the generated MDS matrix contains a zero denominator. {@link Error}
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* @example
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* Generate Poseidon round constants and an MDS matrix from the Grain LFSR.
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*
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* ```ts
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* import { grainGenConstants } from '@noble/curves/abstract/poseidon.js';
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* import { Field } from '@noble/curves/abstract/modular.js';
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* const Fp = Field(17n);
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* const constants = grainGenConstants({ Fp, t: 2, roundsFull: 8, roundsPartial: 8 });
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* ```
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*/
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export function grainGenConstants(opts, skipMDS = 0) {
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const { Fp, t, roundsFull, roundsPartial } = opts;
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// `skipMDS` counts how many candidate matrices to discard before taking one.
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asafenumber(skipMDS, 'skipMDS');
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if (skipMDS < 0)
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throw new Error('invalid number skipMDS');
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const rounds = roundsFull + roundsPartial;
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// `sboxPower` is carried in the opts shape for Poseidon compatibility, but
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// Grain constant generation here only depends on field/size/round counts/inverse flag.
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const sample = poseidonGrain(opts);
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const roundConstants = [];
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for (let r = 0; r < rounds; r++)
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roundConstants.push(sample(t, true));
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if (skipMDS > 0)
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for (let i = 0; i < skipMDS; i++)
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sample(2 * t, false);
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const xs = sample(t, false);
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const ys = sample(t, false);
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// Construct MDS Matrix M[i][j] = 1 / (xs[i] + ys[j])
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const mds = [];
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for (let i = 0; i < t; i++) {
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const row = [];
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for (let j = 0; j < t; j++) {
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const xy = Fp.add(xs[i], ys[j]);
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if (Fp.is0(xy))
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throw new Error(`Error generating MDS matrix: xs[${i}] + ys[${j}] resulted in zero.`);
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row.push(xy);
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}
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mds.push(FpInvertBatch(Fp, row));
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}
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return { roundConstants, mds };
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}
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/**
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* @param opts - Poseidon options. See {@link PoseidonOpts}.
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* @returns Normalized poseidon options.
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* @throws If the Poseidon options, constants, or MDS matrix are invalid. {@link Error}
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* @example
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* Validate generated constants before constructing a permutation.
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*
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* ```ts
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* import { grainGenConstants, validateOpts } from '@noble/curves/abstract/poseidon.js';
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* import { Field } from '@noble/curves/abstract/modular.js';
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* const Fp = Field(17n);
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* const constants = grainGenConstants({ Fp, t: 2, roundsFull: 8, roundsPartial: 8 });
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* const opts = validateOpts({ ...constants, Fp, t: 2, roundsFull: 8, roundsPartial: 8, sboxPower: 3 });
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* ```
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*/
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export function validateOpts(opts) {
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// This only normalizes shapes and field membership for the provided constants;
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// it does not prove the stronger MDS/security criteria discussed in the specs.
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assertValidPosOpts(opts);
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const { Fp, mds, reversePartialPowIdx: rev, roundConstants: rc } = opts;
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const { roundsFull, roundsPartial, sboxPower, t } = opts;
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// MDS is TxT matrix
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if (!Array.isArray(mds) || mds.length !== t)
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throw new Error('Poseidon: invalid MDS matrix');
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const _mds = mds.map((mdsRow) => {
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if (!Array.isArray(mdsRow) || mdsRow.length !== t)
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throw new Error('invalid MDS matrix row: ' + mdsRow);
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return mdsRow.map((i) => {
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if (typeof i !== 'bigint')
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throw new Error('invalid MDS matrix bigint: ' + i);
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// Hardcoded Poseidon MDS matrices often use signed entries like `-1`;
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// accept bigint representatives here and reduce them into the field.
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return Fp.create(i);
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});
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});
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if (rev !== undefined && typeof rev !== 'boolean')
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throw new Error('invalid param reversePartialPowIdx=' + rev);
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if (roundsFull & 1)
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throw new Error('roundsFull is not even' + roundsFull);
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const rounds = roundsFull + roundsPartial;
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if (!Array.isArray(rc) || rc.length !== rounds)
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throw new Error('Poseidon: invalid round constants');
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const roundConstants = rc.map((rc) => {
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if (!Array.isArray(rc) || rc.length !== t)
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throw new Error('invalid round constants');
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return rc.map((i) => {
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if (typeof i !== 'bigint' || !Fp.isValid(i))
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throw new Error('invalid round constant');
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return Fp.create(i);
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});
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});
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// Freeze nested constants so exported handles cannot retune a live permutation instance.
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const freezeRows = (rows) => Object.freeze(rows.map((row) => Object.freeze(row)));
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if (!sboxPower || ![3, 5, 7, 17].includes(sboxPower))
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throw new Error('invalid sboxPower');
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const _sboxPower = BigInt(sboxPower);
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let sboxFn = (n) => FpPow(Fp, n, _sboxPower);
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// Unwrapped sbox power for common cases (195->142μs)
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if (sboxPower === 3)
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sboxFn = (n) => Fp.mul(Fp.sqrN(n), n);
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else if (sboxPower === 5)
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sboxFn = (n) => Fp.mul(Fp.sqrN(Fp.sqrN(n)), n);
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return Object.freeze({
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...opts,
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rounds,
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sboxFn,
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roundConstants: freezeRows(roundConstants),
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mds: freezeRows(_mds),
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});
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}
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/**
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* @param rc - Flattened round constants.
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* @param t - Poseidon width.
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* @returns Constants grouped by round.
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* @throws If the width or flattened constant array is invalid. {@link Error}
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* @example
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* Regroup a flat constant list into per-round chunks.
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*
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* ```ts
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* const rounds = splitConstants([1n, 2n, 3n, 4n], 2);
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* ```
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*/
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export function splitConstants(rc, t) {
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asafenumber(t, 't');
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if (t < 1)
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throw new Error('poseidonSplitConstants: invalid t');
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if (!Array.isArray(rc) || rc.length % t)
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throw new Error('poseidonSplitConstants: invalid rc');
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const res = [];
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let tmp = [];
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for (let i = 0; i < rc.length; i++) {
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const c = rc[i];
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if (typeof c !== 'bigint')
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throw new Error('invalid bigint=' + c);
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tmp.push(c);
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if (tmp.length === t) {
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res.push(tmp);
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tmp = [];
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}
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}
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return res;
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}
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/** Poseidon NTT-friendly hash. */
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/**
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* @param opts - Poseidon options. See {@link PoseidonOpts}.
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* @returns Poseidon permutation.
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* @throws If the Poseidon options or state vector are invalid. {@link Error}
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* @example
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* Build a Poseidon permutation from validated parameters and constants.
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*
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* ```ts
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* import { grainGenConstants, poseidon } from '@noble/curves/abstract/poseidon.js';
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* import { Field } from '@noble/curves/abstract/modular.js';
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* const Fp = Field(17n);
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* const constants = grainGenConstants({ Fp, t: 2, roundsFull: 8, roundsPartial: 8 });
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* const hash = poseidon({ ...constants, Fp, t: 2, roundsFull: 8, roundsPartial: 8, sboxPower: 3 });
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* const state = hash([1n, 2n]);
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* ```
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*/
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export function poseidon(opts) {
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const _opts = validateOpts(opts);
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const { Fp, mds, roundConstants, rounds: totalRounds, roundsPartial, sboxFn, t } = _opts;
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const halfRoundsFull = _opts.roundsFull / 2;
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const partialIdx = _opts.reversePartialPowIdx ? t - 1 : 0;
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const poseidonRound = (values, isFull, idx) => {
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values = values.map((i, j) => Fp.add(i, roundConstants[idx][j]));
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if (isFull)
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values = values.map((i) => sboxFn(i));
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else
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values[partialIdx] = sboxFn(values[partialIdx]);
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// Matrix multiplication
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values = mds.map((i) => i.reduce((acc, i, j) => Fp.add(acc, Fp.mulN(i, values[j])), Fp.ZERO));
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return values;
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};
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const poseidonHash = function poseidonHash(values) {
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if (!Array.isArray(values) || values.length !== t)
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throw new Error('invalid values, expected array of bigints with length ' + t);
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// `.map()` skips sparse holes, which would leak `undefined` into round math below.
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values = values.slice();
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for (let j = 0; j < values.length; j++) {
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const i = values[j];
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if (typeof i !== 'bigint')
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throw new Error('invalid bigint=' + i);
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values[j] = Fp.create(i);
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}
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let lastRound = 0;
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// Apply r_f/2 full rounds.
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for (let i = 0; i < halfRoundsFull; i++)
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values = poseidonRound(values, true, lastRound++);
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// Apply r_p partial rounds.
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for (let i = 0; i < roundsPartial; i++)
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values = poseidonRound(values, false, lastRound++);
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// Apply r_f/2 full rounds.
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for (let i = 0; i < halfRoundsFull; i++)
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values = poseidonRound(values, true, lastRound++);
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if (lastRound !== totalRounds)
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throw new Error('invalid number of rounds');
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return values;
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};
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// For verification in tests
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Object.defineProperty(poseidonHash, 'roundConstants', {
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value: roundConstants,
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enumerable: true,
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});
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return poseidonHash;
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}
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/**
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* @param Fp - Field implementation.
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* @param rate - Sponge rate.
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* @param capacity - Sponge capacity.
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* @param hash - Poseidon permutation.
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* @example
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* Wrap one Poseidon permutation in a sponge interface.
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*
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* ```ts
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* import { PoseidonSponge, grainGenConstants, poseidon } from '@noble/curves/abstract/poseidon.js';
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* import { Field } from '@noble/curves/abstract/modular.js';
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* const Fp = Field(17n);
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* const constants = grainGenConstants({ Fp, t: 2, roundsFull: 8, roundsPartial: 8 });
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* const hash = poseidon({ ...constants, Fp, t: 2, roundsFull: 8, roundsPartial: 8, sboxPower: 3 });
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* const sponge = new PoseidonSponge(Fp, 1, 1, hash);
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* sponge.absorb([1n]);
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* const out = sponge.squeeze(1);
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* ```
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*/
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export class PoseidonSponge {
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Fp;
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rate;
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capacity;
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hash;
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state; // [...capacity, ...rate]
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pos = 0;
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isAbsorbing = true;
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constructor(Fp, rate, capacity, hash) {
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const width = spongeShape(rate, capacity);
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// The direct constructor accepts an arbitrary permutation hook, but callers still
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// need to preserve the `PoseidonFn.roundConstants` width metadata. Reject width
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// mismatches here instead of deferring them until the first `process()` call.
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if (width !== hash.roundConstants[0]?.length)
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throw new Error(`invalid sponge width: expected ${hash.roundConstants[0]?.length}, got ${width}`);
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this.Fp = Fp;
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this.hash = hash;
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this.rate = rate;
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this.capacity = capacity;
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this.state = new Array(width);
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this.clean();
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}
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process() {
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// The permutation is expected to return an owned state array. If callers inject a custom
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// hook that reuses external storage, `clean()` will zero that shared buffer too.
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this.state = this.hash(this.state);
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}
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absorb(input) {
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for (const i of input)
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if (typeof i !== 'bigint' || !this.Fp.isValid(i))
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throw new Error('invalid input: ' + i);
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for (let i = 0; i < input.length;) {
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if (!this.isAbsorbing || this.pos === this.rate) {
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this.process();
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this.pos = 0;
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this.isAbsorbing = true;
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}
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const chunk = Math.min(this.rate - this.pos, input.length - i);
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for (let j = 0; j < chunk; j++) {
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const idx = this.capacity + this.pos++;
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this.state[idx] = this.Fp.add(this.state[idx], input[i++]);
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}
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}
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}
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squeeze(count) {
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// Rust oracles use unsigned counts. In JS we keep `squeeze(0) => []` for
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// compatibility, but still reject negative/fractional counts explicitly.
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asafenumber(count, 'count');
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if (count < 0)
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throw new Error('invalid number count');
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const res = [];
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while (res.length < count) {
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if (this.isAbsorbing || this.pos === this.rate) {
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this.process();
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this.pos = 0;
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this.isAbsorbing = false;
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}
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const chunk = Math.min(this.rate - this.pos, count - res.length);
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for (let i = 0; i < chunk; i++)
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res.push(this.state[this.capacity + this.pos++]);
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}
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return res;
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}
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clean() {
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this.state.fill(this.Fp.ZERO);
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this.isAbsorbing = true;
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this.pos = 0;
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}
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clone() {
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const c = new PoseidonSponge(this.Fp, this.rate, this.capacity, this.hash);
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c.pos = this.pos;
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c.isAbsorbing = this.isAbsorbing;
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c.state = [...this.state];
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return c;
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}
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}
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const spongeShape = (rate, capacity) => {
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asafenumber(rate, 'rate');
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asafenumber(capacity, 'capacity');
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// A sponge with zero rate cannot absorb or squeeze any field elements.
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if (rate < 1)
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throw new Error('invalid number rate');
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// Negative capacity can accidentally keep `rate + capacity` coherent while still
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// producing a nonsensical sponge shape.
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if (capacity < 0)
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throw new Error('invalid number capacity');
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return rate + capacity;
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};
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/**
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* The method is not defined in spec, but nevertheless used often.
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* Check carefully for compatibility: there are many edge cases, like absorbing an empty array.
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* We cross-test against:
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* - {@link https://github.com/ProvableHQ/snarkVM/tree/staging/algorithms | snarkVM algorithms}
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* - {@link https://github.com/arkworks-rs/crypto-primitives/tree/main | arkworks crypto-primitives}
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* @param opts - Sponge options. See {@link PoseidonSpongeOpts}.
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* @returns Factory for sponge instances.
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* @throws If the sponge dimensions or backing permutation options are invalid. {@link Error}
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* @example
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* Use the sponge helper to absorb several field elements and squeeze one digest.
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*
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* ```ts
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* import { grainGenConstants, poseidonSponge } from '@noble/curves/abstract/poseidon.js';
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* import { Field } from '@noble/curves/abstract/modular.js';
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* const Fp = Field(17n);
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* const constants = grainGenConstants({ Fp, t: 2, roundsFull: 8, roundsPartial: 8 });
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* const makeSponge = poseidonSponge({
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* ...constants,
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* Fp,
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* rate: 1,
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* capacity: 1,
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* roundsFull: 8,
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* roundsPartial: 8,
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* sboxPower: 3,
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* });
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* const sponge = makeSponge();
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* sponge.absorb([1n]);
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* const out = sponge.squeeze(1);
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* ```
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*/
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export function poseidonSponge(opts) {
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const { rate, capacity } = opts;
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const t = spongeShape(rate, capacity);
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// Re-use one hash instance between sponge instances; isolation depends on
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// poseidon(...) itself staying immutable and not carrying mutable call state.
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const hash = poseidon({ ...opts, t });
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const { Fp } = opts;
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return (() => new PoseidonSponge(Fp, rate, capacity, hash));
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}
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//# sourceMappingURL=poseidon.js.map
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