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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,142 @@ | ||
| const crypto = require('crypto'); | ||
| const $ = require('../util/preconditions'); | ||
| const JS = require('../util/js'); | ||
| const BN = require('./bn'); | ||
| const Point = require('./point'); | ||
| const TaggedHash = require('./taggedhash'); | ||
|
|
||
| const Schnorr = function Schnorr() { | ||
| if (!(this instanceof Schnorr)) { | ||
| return new Schnorr(); | ||
| } | ||
| return this; | ||
| }; | ||
|
|
||
| Schnorr.prototype.set = function() {}; | ||
|
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||
| /** | ||
| * Create a schnorr signature | ||
| * @param {PrivateKey|Buffer|BN} privateKey | ||
| * @param {String|Buffer} message Hex string or buffer | ||
| * @param {String|Buffer} aux Hex string or buffer | ||
| * @returns {Buffer} | ||
| * @link https://github.com/bitcoin/bips/blob/master/bip-0340.mediawiki#Default_Signing | ||
| */ | ||
| Schnorr.sign = function(privateKey, message, aux) { | ||
| privateKey = Buffer.isBuffer(privateKey) ? privateKey : privateKey.toBuffer(); | ||
| if (privateKey.length !== 32) { | ||
| throw new Error('Private key should be 32 bytes for schnorr signatures'); | ||
| } | ||
|
|
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| if (typeof message === 'string') { | ||
| $.checkArgument(JS.isHexaString(message), 'Schnorr message string is not hex'); | ||
| message = Buffer.from(message, 'hex') | ||
| } | ||
| $.checkArgument($.isType(message, 'Buffer'), 'Schnorr message must be a hex string or buffer'); | ||
|
|
||
| if (!aux) { | ||
| aux = crypto.randomBytes(32); | ||
| } | ||
| if (typeof aux === 'string') { | ||
| $.checkArgument(JS.isHexaString(aux), 'Schnorr aux string is not hex'); | ||
| aux = Buffer.from(aux, 'hex') | ||
| } | ||
| $.checkArgument($.isType(aux, 'Buffer'), 'Schnorr aux must be a hex string or buffer'); | ||
|
|
||
| const G = Point.getG(); | ||
| const n = Point.getN(); | ||
|
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||
| const dPrime = new BN(privateKey); | ||
| if (dPrime.eqn(0) || dPrime.gte(n)) { | ||
| throw new Error('Invalid private key for schnorr signing'); | ||
| } | ||
| const P = G.mul(dPrime); | ||
| const Pbuf = Buffer.from(P.encodeCompressed().slice(1)); // slice(1) removes the encoding prefix byte | ||
| const d = P.y.isEven() ? dPrime : n.sub(dPrime); | ||
| const t = d.xor(new BN(new TaggedHash('BIP0340/aux', aux).finalize())); | ||
| const rand = new TaggedHash('BIP0340/nonce', Buffer.concat([t.toBuffer(), Pbuf, message])).finalize(); | ||
| const kPrime = new BN(rand).mod(n); | ||
| if (kPrime.eqn(0)) { | ||
| throw new Error('Error creating schnorr signature'); | ||
| } | ||
| const R = G.mul(kPrime); | ||
| const Rbuf = Buffer.from(R.encodeCompressed().slice(1)); // slice(1) removes the encoding prefix byte | ||
| const k = R.y.isEven() ? kPrime : n.sub(kPrime); | ||
| const e = new BN(new TaggedHash('BIP0340/challenge', Buffer.concat([Rbuf, Pbuf, message])).finalize()).mod(n); | ||
| const sig = Buffer.concat([Rbuf, k.add(e.mul(d)).mod(n).toBuffer()]); | ||
|
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||
| if (!Schnorr.verify(Pbuf, message, sig)) { | ||
| throw new Error('Error creating schnorr signature. Verification failed'); | ||
| } | ||
| return sig; | ||
| }; | ||
|
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||
|
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| /** | ||
| * Verify a schnorr signature | ||
| * @param {PublicKey|Buffer} publicKey | ||
| * @param {String|Buffer} message Hex string or buffer | ||
| * @param {String|Signature|Buffer} signature Hex string, Signature instance, or buffer | ||
| * @returns {Boolean} | ||
| * @link https://github.com/bitcoin/bips/blob/master/bip-0340.mediawiki#Verification | ||
| */ | ||
| Schnorr.verify = function(publicKey, message, signature) { | ||
| if ($.isType(publicKey, 'PublicKey')) { | ||
| publicKey = publicKey.point.x.toBuffer(); | ||
| } | ||
| if (publicKey.length !== 32) { | ||
| throw new Error('Public key should be 32 bytes for schnorr signatures'); | ||
| } | ||
|
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||
| if (typeof message === 'string') { | ||
| $.checkArgument(JS.isHexaString(message), 'Schnorr message string is not hex'); | ||
| message = Buffer.from(message, 'hex'); | ||
| } | ||
| if (message.length !== 32) { | ||
| throw new Error('Message should be a 32 byte buffer'); | ||
| } | ||
|
|
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| if (typeof signature === 'string') { | ||
| $.checkArgument(JS.isHexaString(signature), 'Schnorr signature string is not hex'); | ||
| signature = Buffer.from(signature, 'hex'); | ||
| } | ||
| if (typeof signature.toBuffer === 'function') { | ||
| signature = signature.toBuffer(); | ||
| if (signature.length === 65) { | ||
| signature = signature.slice(0, 64); // remove the sighashType byte | ||
| } | ||
| } | ||
| if (signature.length !== 64) { | ||
| throw new Error('Signature should be a 64 byte buffer'); | ||
| } | ||
|
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||
| try { | ||
| const p = Point.getP(); | ||
| const n = Point.getN(); | ||
|
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| const P = Point.fromX(false, publicKey).liftX(); | ||
| const r = new BN(signature.slice(0, 32)); | ||
| const s = new BN(signature.slice(32, 64)); | ||
| if (r.gte(p) || s.gte(n)) { | ||
| return false; | ||
| } | ||
| const e = getE(r, P, message); | ||
| const G = Point.getG(); | ||
| const R = G.mul(s).add(P.mul(e).neg()); | ||
| if (R.inf || !R.y.isEven() || !R.x.eq(r)) { | ||
| return false; | ||
| } | ||
| return true; | ||
| } catch (e) { | ||
| return false; | ||
| } | ||
| }; | ||
|
|
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| /* Utility function used in Verify() */ | ||
| const getE = function(r, P, message) { | ||
| const n = Point.getN(); | ||
| const hash = new TaggedHash('BIP0340/challenge', Buffer.concat([r.toBuffer({ size: 32 }), P.x.toBuffer({ size: 32 }), message])).finalize(); | ||
| return new BN(hash).mod(n); | ||
| }; | ||
|
|
||
| module.exports = Schnorr; |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,52 @@ | ||
| const Hash = require('./hash'); | ||
| const BufferWriter = require('../encoding/bufferwriter'); | ||
| const inherits = require('inherits'); | ||
|
|
||
| /** | ||
| * Creates a tag hash to ensure uniqueness of a message between purposes. | ||
| * For example, if there's a potential for a collision of messages between | ||
| * multiple purposes, a tag can be added to guard against such collisions. | ||
| * @link https://github.com/bitcoin/bips/blob/master/bip-0340.mediawiki#Design (see 'Tagged Hashes') | ||
| * @param {String} tag The tag to prevent message collisions. Should uniquely reflect the purpose of the message. | ||
| * @param {Buffer|String} message (optional) | ||
| * @param {String} messageEncoding (default: 'hex') If `message` is a string, provide the encoding | ||
| * @returns {TaggedHash} Instance of a BufferWriter with the written tag and `finalize` method | ||
| */ | ||
| function TaggedHash(tag, message, messageEncoding = 'hex') { | ||
| if (!(this instanceof TaggedHash)) { | ||
| return new TaggedHash(tag, message, messageEncoding); | ||
| } | ||
| BufferWriter.apply(this); | ||
| tag = Buffer.from(tag); | ||
|
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| const taghash = Hash.sha256(tag); | ||
| this.write(taghash); | ||
| this.write(taghash); | ||
| if (message) { | ||
| message = Buffer.isBuffer(message) ? message : Buffer.from(message, messageEncoding); | ||
| this.write(message); | ||
| } | ||
| return this; | ||
| }; | ||
|
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| inherits(TaggedHash, BufferWriter); | ||
|
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| /** | ||
| * Returns a 32-byte SHA256 hash of the double tagged hashes concat'd with the message | ||
| * as defined by BIP-340: SHA256(SHA256(tag), SHA256(tag), message) | ||
| * @returns {Buffer} | ||
| */ | ||
| TaggedHash.prototype.finalize = function() { | ||
| return Buffer.from(Hash.sha256(this.toBuffer())); | ||
| }; | ||
|
|
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| /** | ||
| * Commonly used tags | ||
| */ | ||
| Object.defineProperties(TaggedHash, { | ||
| TAPSIGHASH: { get: () => new TaggedHash('TapSighash') }, | ||
| TAPLEAF: { get: () => new TaggedHash('TapLeaf') }, | ||
| TAPBRANCH: { get: () => new TaggedHash('TapBranch') } | ||
| }); | ||
|
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| module.exports = TaggedHash; |
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