mirror of
https://github.com/pezkuwichain/pezkuwi-wasm.git
synced 2026-04-21 23:48:00 +00:00
472 lines
17 KiB
JavaScript
472 lines
17 KiB
JavaScript
/**
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* Minimal JS implementation of sr25519 cryptography for Pezkuwi.
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*
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* Uses [Merlin](https://merlin.cool/index.html),
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* a transcript construction, built on [Strobe](https://strobe.sourceforge.io).
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* Merlin ensures two parties agree on the same state when communicating.
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*
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* More: https://wiki.pezkuwi.network/docs/learn-cryptography.
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*/
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import { mod } from '@noble/curves/abstract/modular.js';
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import { aInRange, bitMask, bytesToNumberLE, equalBytes, isBytes, numberToBytesLE, } from '@noble/curves/abstract/utils.js';
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import { ed25519, RistrettoPoint } from '@noble/curves/ed25519.js';
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import { keccakP } from '@noble/hashes/sha3.js';
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import { sha512 } from '@noble/hashes/sha512.js';
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import { concatBytes, randomBytes, u32, utf8ToBytes } from '@noble/hashes/utils.js';
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// prettier-ignore
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const _0n = BigInt(0), _3n = BigInt(3);
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function toData(d) {
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if (typeof d === 'string')
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return utf8ToBytes(d);
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if (isBytes(d))
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return d;
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throw new Error('Wrong data');
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}
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// Could've used bytes from hashes/assert, but we add extra arg
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function abytes(title, b, ...lengths) {
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if (!isBytes(b))
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throw new Error(`${title}: Uint8Array expected`);
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if (lengths.length && !lengths.includes(b.length))
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throw new Error(`${title}: Uint8Array expected of length ${lengths}, not of length=${b.length}`);
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}
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function checkU32(title, n) {
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if (!Number.isSafeInteger(n) || n < 0 || n > 4294967295)
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throw new Error(`${title}: wrong u32 integer: ${n}`);
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return n;
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}
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function cleanBytes(...list) {
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for (const t of list)
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t.fill(0);
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}
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const EMPTY = Uint8Array.of();
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const CURVE_ORDER = ed25519.CURVE.n;
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function parseScalar(title, bytes) {
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abytes(title, bytes, 32);
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const n = bytesToNumberLE(bytes);
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aInRange(title, n, _0n, CURVE_ORDER);
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return n;
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}
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const modN = (n) => mod(n, CURVE_ORDER);
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// STROBE128 (minimal version required for Merlin)
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// - https://strobe.sourceforge.io/specs/
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// We can implement full version, but seems nobody uses this much.
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const STROBE_R = 166;
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const Flags = {
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I: 1,
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A: 1 << 1,
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C: 1 << 2,
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T: 1 << 3,
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M: 1 << 4,
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K: 1 << 5,
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};
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// Differences: suffix, additional methods/flags
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class Strobe128 {
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constructor(protocolLabel) {
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this.state = new Uint8Array(200);
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this.pos = 0;
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this.posBegin = 0;
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this.curFlags = 0;
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this.state.set([1, STROBE_R + 2, 1, 0, 1, 96], 0);
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this.state.set(utf8ToBytes('STROBEv1.0.2'), 6);
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this.state32 = u32(this.state);
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this.keccakF1600();
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this.metaAD(protocolLabel, false);
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}
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keccakF1600() {
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keccakP(this.state32);
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}
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runF() {
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this.state[this.pos] ^= this.posBegin;
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this.state[this.pos + 1] ^= 0x04;
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this.state[STROBE_R + 1] ^= 0x80;
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this.keccakF1600();
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this.pos = 0;
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this.posBegin = 0;
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}
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// keccak.update()
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absorb(data) {
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for (let i = 0; i < data.length; i++) {
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this.state[this.pos++] ^= data[i];
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if (this.pos === STROBE_R)
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this.runF();
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}
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}
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// keccak.xof()
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squeeze(len) {
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const data = new Uint8Array(len);
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for (let i = 0; i < data.length; i++) {
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data[i] = this.state[this.pos];
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this.state[this.pos++] = 0;
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if (this.pos === STROBE_R)
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this.runF();
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}
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return data;
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}
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overwrite(data) {
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for (let i = 0; i < data.length; i++) {
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this.state[this.pos++] = data[i];
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if (this.pos === STROBE_R)
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this.runF();
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}
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}
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beginOp(flags, more) {
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if (more) {
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if (this.curFlags !== flags) {
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throw new Error(`Continued op with changed flags from ${this.curFlags.toString(2)} to ${flags.toString(2)}`);
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}
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return;
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}
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if ((flags & Flags.T) !== 0)
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throw new Error('T flag is not supported');
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const oldBegin = this.posBegin;
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this.posBegin = this.pos + 1;
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this.curFlags = flags;
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this.absorb(new Uint8Array([oldBegin, flags]));
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const forceF = (flags & (Flags.C | Flags.K)) !== 0;
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if (forceF && this.pos !== 0)
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this.runF();
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}
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// Public API
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metaAD(data, more) {
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this.beginOp(Flags.M | Flags.A, more);
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this.absorb(toData(data));
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}
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AD(data, more) {
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this.beginOp(Flags.A, more);
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this.absorb(toData(data));
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}
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PRF(len, more) {
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this.beginOp(Flags.I | Flags.A | Flags.C, more);
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return this.squeeze(len);
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}
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KEY(data, more) {
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this.beginOp(Flags.A | Flags.C, more);
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this.overwrite(toData(data));
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}
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// Utils
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clone() {
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const n = new Strobe128('0'); // tmp
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n.pos = this.pos;
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n.posBegin = this.posBegin;
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n.state.set(this.state);
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n.curFlags = this.curFlags;
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return n;
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}
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clean() {
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this.state.fill(0); // also clears state32, because same buffer
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this.pos = 0;
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this.curFlags = 0;
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this.posBegin = 0;
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}
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}
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// /STROBE128
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// Merlin
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// https://merlin.cool/index.html
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class Merlin {
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constructor(label) {
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this.strobe = new Strobe128('Merlin v1.0');
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this.appendMessage('dom-sep', label);
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}
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appendMessage(label, message) {
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this.strobe.metaAD(label, false);
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checkU32('Merlin.appendMessage', message.length);
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this.strobe.metaAD(numberToBytesLE(message.length, 4), true);
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this.strobe.AD(message, false);
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}
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challengeBytes(label, len) {
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this.strobe.metaAD(label, false);
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checkU32('Merlin.challengeBytes', len);
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this.strobe.metaAD(numberToBytesLE(len, 4), true);
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return this.strobe.PRF(len, false);
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}
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clean() {
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this.strobe.clean();
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}
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}
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// /Merlin
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// Merlin signging context/transcript (sr25519 specific stuff, Merlin and Strobe are generic (but minimal))
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class SigningContext extends Merlin {
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constructor(name, rng = randomBytes) {
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super(name);
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this.rng = rng;
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}
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label(label) {
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this.appendMessage('', label);
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}
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bytes(bytes) {
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this.appendMessage('sign-bytes', bytes);
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return this;
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}
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protoName(label) {
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this.appendMessage('proto-name', label);
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}
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commitPoint(label, point) {
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this.appendMessage(label, point.toRawBytes());
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}
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challengeScalar(label) {
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return modN(bytesToNumberLE(this.challengeBytes(label, 64)));
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}
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witnessScalar(label, nonceSeeds = []) {
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return modN(bytesToNumberLE(this.witnessBytes(label, 64, nonceSeeds)));
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}
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witnessBytes(label, len, nonceSeeds = []) {
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checkU32('SigningContext.witnessBytes', len);
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const strobeRng = this.strobe.clone();
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for (const ns of nonceSeeds) {
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strobeRng.metaAD(label, false);
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checkU32('SigningContext.witnessBytes nonce length', ns.length);
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strobeRng.metaAD(numberToBytesLE(ns.length, 4), true);
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strobeRng.KEY(ns, false);
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}
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const random = this.rng(32);
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strobeRng.metaAD('rng', false);
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strobeRng.KEY(random, false);
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strobeRng.metaAD(numberToBytesLE(len, 4), false);
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return strobeRng.PRF(len, false);
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}
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}
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// /Merlin signing context
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const MASK = bitMask(256);
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// == (n * CURVE.h) % CURVE_BIT_MASK
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const encodeScalar = (n) => numberToBytesLE((n << _3n) & MASK, 32);
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// n / CURVE.h
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const decodeScalar = (n) => bytesToNumberLE(n) >> _3n;
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// NOTE: secretKey is 64 bytes (key + nonce). This required for HDKD, since key can be derived not only from seed, but from other keys.
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export function getPublicKey(secretKey) {
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abytes('secretKey', secretKey, 64);
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const scalar = decodeScalar(secretKey.subarray(0, 32));
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return RistrettoPoint.BASE.multiply(scalar).toRawBytes();
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}
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export function secretFromSeed(seed) {
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abytes('seed', seed, 32);
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const r = sha512(seed);
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// NOTE: different from ed25519
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r[0] &= 248;
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r[31] &= 63;
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r[31] |= 64;
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// this will strip upper 3 bits and lower 3 bits
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const key = encodeScalar(decodeScalar(r.subarray(0, 32)));
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const nonce = r.subarray(32, 64);
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const res = concatBytes(key, nonce);
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cleanBytes(key, nonce, r);
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return res;
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}
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// Seems like ed25519 keypair? Generates keypair from other keypair in ed25519 format
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// NOTE: not exported from wasm. Do we need this at all?
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export function fromKeypair(pair) {
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abytes('keypair', pair, 96);
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const sk = pair.subarray(0, 32);
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const nonce = pair.subarray(32, 64);
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const pubBytes = pair.subarray(64, 96);
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const key = encodeScalar(bytesToNumberLE(sk));
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const realPub = getPublicKey(pair.subarray(0, 64));
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if (!equalBytes(pubBytes, realPub))
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throw new Error('wrong public key');
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// No need to clean since subarray's
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return concatBytes(key, nonce, realPub);
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}
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// Basic sign. NOTE: context is currently constant. Please open issue if you need different one.
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const BIZINIKIWI_CONTEXT = utf8ToBytes('bizinikiwi');
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export function sign(secretKey, message, rng = randomBytes) {
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abytes('message', message);
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abytes('secretKey', secretKey, 64);
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const t = new SigningContext('SigningContext', rng);
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t.label(BIZINIKIWI_CONTEXT);
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t.bytes(message);
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const keyScalar = decodeScalar(secretKey.subarray(0, 32));
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const nonce = secretKey.subarray(32, 64);
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const pubPoint = RistrettoPoint.fromHex(getPublicKey(secretKey));
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t.protoName('Schnorr-sig');
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t.commitPoint('sign:pk', pubPoint);
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const r = t.witnessScalar('signing', [nonce]);
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const R = RistrettoPoint.BASE.multiply(r);
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t.commitPoint('sign:R', R);
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const k = t.challengeScalar('sign:c');
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const s = modN(k * keyScalar + r);
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const res = concatBytes(R.toRawBytes(), numberToBytesLE(s, 32));
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res[63] |= 128; // add Schnorrkel marker
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t.clean();
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return res;
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}
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export function verify(message, signature, publicKey) {
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abytes('message', message);
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abytes('signature', signature, 64);
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abytes('publicKey', publicKey, 32);
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if ((signature[63] & 128) === 0)
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throw new Error('Schnorrkel marker missing');
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const sBytes = Uint8Array.from(signature.subarray(32, 64)); // copy before modification
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sBytes[31] &= 127; // remove Schnorrkel marker
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const R = RistrettoPoint.fromHex(signature.subarray(0, 32));
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const s = bytesToNumberLE(sBytes);
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aInRange('s', s, _0n, CURVE_ORDER); // Just in case, it will be checked at multiplication later
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const t = new SigningContext('SigningContext');
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t.label(BIZINIKIWI_CONTEXT);
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t.bytes(message);
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const pubPoint = RistrettoPoint.fromHex(publicKey);
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if (pubPoint.equals(RistrettoPoint.ZERO))
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return false;
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t.protoName('Schnorr-sig');
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t.commitPoint('sign:pk', pubPoint);
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t.commitPoint('sign:R', R);
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const k = t.challengeScalar('sign:c');
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const sP = RistrettoPoint.BASE.multiply(s);
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const RR = pubPoint.negate().multiply(k).add(sP);
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t.clean();
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cleanBytes(sBytes);
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return RR.equals(R);
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}
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export function getSharedSecret(secretKey, publicKey) {
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abytes('secretKey', secretKey, 64);
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abytes('publicKey', publicKey, 32);
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const keyScalar = decodeScalar(secretKey.subarray(0, 32));
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const pubPoint = RistrettoPoint.fromHex(publicKey);
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if (pubPoint.equals(RistrettoPoint.ZERO))
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throw new Error('wrong public key (infinity)');
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return pubPoint.multiply(keyScalar).toRawBytes();
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}
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// Derive
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export const HDKD = {
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secretSoft(secretKey, chainCode, rng = randomBytes) {
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abytes('secretKey', secretKey, 64);
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abytes('chainCode', chainCode, 32);
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const masterScalar = decodeScalar(secretKey.subarray(0, 32));
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const masterNonce = secretKey.subarray(32, 64);
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const pubPoint = RistrettoPoint.fromHex(getPublicKey(secretKey));
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const t = new SigningContext('SchnorrRistrettoHDKD', rng);
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t.bytes(EMPTY);
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t.appendMessage('chain-code', chainCode);
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t.commitPoint('public-key', pubPoint);
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const scalar = t.challengeScalar('HDKD-scalar');
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const hdkdChainCode = t.challengeBytes('HDKD-chaincode', 32);
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const nonceSeed = concatBytes(numberToBytesLE(masterScalar, 32), masterNonce);
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const nonce = t.witnessBytes('HDKD-nonce', 32, [masterNonce, nonceSeed]);
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const key = encodeScalar(modN(masterScalar + scalar));
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const res = concatBytes(key, nonce);
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cleanBytes(key, nonce, nonceSeed, hdkdChainCode);
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t.clean();
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return res;
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},
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publicSoft(publicKey, chainCode) {
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abytes('publicKey', publicKey, 32);
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abytes('chainCode', chainCode, 32);
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const pubPoint = RistrettoPoint.fromHex(publicKey);
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const t = new SigningContext('SchnorrRistrettoHDKD');
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t.bytes(EMPTY);
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t.appendMessage('chain-code', chainCode);
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t.commitPoint('public-key', pubPoint);
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const scalar = t.challengeScalar('HDKD-scalar');
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t.challengeBytes('HDKD-chaincode', 32);
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t.clean();
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return pubPoint.add(RistrettoPoint.BASE.multiply(scalar)).toRawBytes();
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},
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secretHard(secretKey, chainCode) {
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abytes('secretKey', secretKey, 64);
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abytes('chainCode', chainCode, 32);
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const key = numberToBytesLE(decodeScalar(secretKey.subarray(0, 32)), 32);
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const t = new SigningContext('SchnorrRistrettoHDKD');
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t.bytes(EMPTY);
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t.appendMessage('chain-code', chainCode);
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t.appendMessage('secret-key', key);
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const msk = t.challengeBytes('HDKD-hard', 32);
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const hdkdChainCode = t.challengeBytes('HDKD-chaincode', 32);
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t.clean();
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const res = secretFromSeed(msk);
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cleanBytes(key, msk, hdkdChainCode);
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t.clean();
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return res;
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},
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};
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const dleq = {
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proove(keyScalar, nonce, pubPoint, t, input, output) {
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t.protoName('DLEQProof');
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t.commitPoint('vrf:h', input);
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const r = t.witnessScalar(`proving${'\0'}0`, [nonce]);
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const R = RistrettoPoint.BASE.multiply(r);
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t.commitPoint('vrf:R=g^r', R);
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const Hr = input.multiply(r);
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t.commitPoint('vrf:h^r', Hr);
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t.commitPoint('vrf:pk', pubPoint);
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t.commitPoint('vrf:h^sk', output);
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const c = t.challengeScalar('prove');
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const s = modN(r - c * keyScalar);
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return { proof: { c, s }, proofBatchable: { R, Hr, s } };
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},
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verify(pubPoint, t, input, output, proof) {
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if (pubPoint.equals(RistrettoPoint.ZERO))
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return false;
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t.protoName('DLEQProof');
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t.commitPoint('vrf:h', input);
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const R = pubPoint.multiply(proof.c).add(RistrettoPoint.BASE.multiply(proof.s));
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t.commitPoint('vrf:R=g^r', R);
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const Hr = output.multiply(proof.c).add(input.multiply(proof.s));
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t.commitPoint('vrf:h^r', Hr);
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t.commitPoint('vrf:pk', pubPoint);
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t.commitPoint('vrf:h^sk', output);
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const realC = t.challengeScalar('prove');
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if (proof.c === realC)
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return { R, Hr, s: proof.s }; // proofBatchable
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return false;
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},
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};
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// VRF: Verifiable Random Function
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function initVRF(ctx, msg, extra, pubPoint, rng = randomBytes) {
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const t = new SigningContext('SigningContext', rng);
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t.label(ctx);
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t.bytes(msg);
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t.commitPoint('vrf-nm-pk', pubPoint);
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const hash = t.challengeBytes('VRFHash', 64);
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const input = RistrettoPoint.hashToCurve(hash);
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const transcript = new SigningContext('VRF', rng);
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if (extra.length)
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transcript.label(extra);
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t.clean();
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cleanBytes(hash);
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return { input, t: transcript };
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}
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export const vrf = {
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sign(msg, secretKey, ctx = EMPTY, extra = EMPTY, rng = randomBytes) {
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abytes('msg', msg);
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abytes('secretKey', secretKey, 64);
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abytes('ctx', ctx);
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abytes('extra', extra);
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const keyScalar = decodeScalar(secretKey.subarray(0, 32));
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const nonce = secretKey.subarray(32, 64);
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const pubPoint = RistrettoPoint.fromHex(getPublicKey(secretKey));
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const { input, t } = initVRF(ctx, msg, extra, pubPoint, rng);
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const output = input.multiply(keyScalar);
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const p = { input, output };
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const { proof } = dleq.proove(keyScalar, nonce, pubPoint, t, input, output);
|
|
const cBytes = numberToBytesLE(proof.c, 32);
|
|
const sBytes = numberToBytesLE(proof.s, 32);
|
|
const res = concatBytes(p.output.toRawBytes(), cBytes, sBytes);
|
|
cleanBytes(nonce, cBytes, sBytes);
|
|
return res;
|
|
},
|
|
verify(msg, signature, publicKey, ctx = EMPTY, extra = EMPTY, rng = randomBytes) {
|
|
abytes('msg', msg);
|
|
abytes('signature', signature, 96); // O(point) || c(scalar) || s(scalar)
|
|
abytes('pubkey', publicKey, 32);
|
|
abytes('ctx', ctx);
|
|
abytes('extra', extra);
|
|
const pubPoint = RistrettoPoint.fromHex(publicKey);
|
|
if (pubPoint.equals(RistrettoPoint.ZERO))
|
|
return false;
|
|
const proof = {
|
|
c: parseScalar('signature.c', signature.subarray(32, 64)),
|
|
s: parseScalar('signature.s', signature.subarray(64, 96)),
|
|
};
|
|
const { input, t } = initVRF(ctx, msg, extra, pubPoint, rng);
|
|
const output = RistrettoPoint.fromHex(signature.subarray(0, 32));
|
|
if (output.equals(RistrettoPoint.ZERO))
|
|
throw new Error('vrf.verify: wrong output point (identity)');
|
|
const proofBatchable = dleq.verify(pubPoint, t, input, output, proof);
|
|
return proofBatchable === false ? false : true;
|
|
},
|
|
};
|
|
// NOTE: for tests only, don't use
|
|
export const __tests = {
|
|
Strobe128,
|
|
Merlin,
|
|
SigningContext,
|
|
};
|
|
//# sourceMappingURL=index.js.map
|