85 lines
2.5 KiB
JavaScript
85 lines
2.5 KiB
JavaScript
const { ethers } = require('hardhat')
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const { BigNumber } = ethers
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const { randomBN, poseidonHash, toBuffer } = require('./utils')
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const { Keypair } = require('./keypair')
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class Utxo {
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/** Initialize a new UTXO - unspent transaction output or input. Note, a full TX consists of 2/16 inputs and 2 outputs
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*
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* @param {BigNumber | BigInt | number | string} amount UTXO amount
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* @param {BigNumber | BigInt | number | string} blinding Blinding factor
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* @param {Keypair} keypair
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* @param {number|null} index UTXO index in the merkle tree
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*/
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constructor({ amount = 0, keypair = new Keypair(), blinding = randomBN(), index = null } = {}) {
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this.amount = BigNumber.from(amount)
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this.blinding = BigNumber.from(blinding)
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this.keypair = keypair
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this.index = index
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}
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/**
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* Returns commitment for this UTXO
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*
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* @returns {BigNumber}
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*/
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getCommitment() {
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if (!this._commitment) {
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this._commitment = poseidonHash([this.amount, this.keypair.pubkey, this.blinding])
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}
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return this._commitment
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}
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/**
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* Returns nullifier for this UTXO
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*
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* @returns {BigNumber}
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*/
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getNullifier() {
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if (!this._nullifier) {
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if (
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this.amount > 0 &&
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(this.index === undefined ||
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this.index === null ||
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this.keypair.privkey === undefined ||
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this.keypair.privkey === null)
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) {
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throw new Error('Can not compute nullifier without utxo index or private key')
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}
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const signature = this.keypair.privkey ? this.keypair.sign(this.getCommitment(), this.index || 0) : 0
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this._nullifier = poseidonHash([this.getCommitment(), this.index || 0, signature])
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}
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return this._nullifier
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}
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/**
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* Encrypt UTXO data using the current keypair
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*
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* @returns {string} `0x`-prefixed hex string with data
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*/
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encrypt() {
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const bytes = Buffer.concat([toBuffer(this.amount, 31), toBuffer(this.blinding, 31)])
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return this.keypair.encrypt(bytes)
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}
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/**
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* Decrypt a UTXO
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*
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* @param {Keypair} keypair keypair used to decrypt
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* @param {string} data hex string with data
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* @param {number} index UTXO index in merkle tree
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* @returns {Utxo}
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*/
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static decrypt(keypair, data, index) {
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const buf = keypair.decrypt(data)
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return new Utxo({
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amount: BigNumber.from('0x' + buf.slice(0, 31).toString('hex')),
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blinding: BigNumber.from('0x' + buf.slice(31, 62).toString('hex')),
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keypair,
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index,
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})
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}
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}
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module.exports = Utxo
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