From a19a22627721baf287d962bcb674166cc830198c Mon Sep 17 00:00:00 2001
From: poma <semenov.roma@gmail.com>
Date: Wed, 9 Jun 2021 14:19:22 +0300
Subject: [PATCH] keypair

---
 src/index.js   |  6 +++---
 src/kaypair.js | 31 +++++++++++++++++++++++++++++++
 src/utxo.js    | 30 ++++++++----------------------
 3 files changed, 42 insertions(+), 25 deletions(-)
 create mode 100644 src/kaypair.js

diff --git a/src/index.js b/src/index.js
index 2c2345e..3a02403 100644
--- a/src/index.js
+++ b/src/index.js
@@ -66,7 +66,7 @@ async function getProof({ inputs, outputs, tree, extAmount, fee, recipient, rela
 
     // data for 2 transaction inputs
     inAmount: inputs.map((x) => x.amount),
-    inPrivateKey: inputs.map((x) => x.privkey),
+    inPrivateKey: inputs.map((x) => x.keypair.privkey),
     inBlinding: inputs.map((x) => x.blinding),
     inPathIndices: inputMerklePathIndices,
     inPathElements: inputMerklePathElements,
@@ -74,7 +74,7 @@ async function getProof({ inputs, outputs, tree, extAmount, fee, recipient, rela
     // data for 2 transaction outputs
     outAmount: outputs.map((x) => x.amount),
     outBlinding: outputs.map((x) => x.blinding),
-    outPubkey: outputs.map((x) => x.pubkey),
+    outPubkey: outputs.map((x) => x.keypair.pubkey),
     outPathIndices: outputIndex >> Math.log2(outputs.length),
     outPathElements: outputPath.slice(Math.log2(outputs.length)),
   }
@@ -130,7 +130,7 @@ async function transact({ tornadoPool, utxo }) {
   const inputs = [utxo, new Utxo()]
   const outputs = [
     new Utxo({ amount: utxo.amount / 4 }),
-    new Utxo({ amount: (utxo.amount * 3) / 4, privkey: utxo.privkey }),
+    new Utxo({ amount: (utxo.amount * 3) / 4, keypair: utxo.keypair }),
   ]
 
   const { proof, args } = await getProof({
diff --git a/src/kaypair.js b/src/kaypair.js
new file mode 100644
index 0000000..feefcd0
--- /dev/null
+++ b/src/kaypair.js
@@ -0,0 +1,31 @@
+const { ethers } = require('hardhat')
+const { BigNumber } = ethers
+const { randomBN, poseidonHash, toFixedHex } = require('./utils')
+
+class Keypair {
+  constructor(privkey = randomBN()) {
+    this.privkey = privkey
+    this.pubkey = poseidonHash([this.privkey])
+    this.encryptionKey = 0 // todo
+  }
+
+  toString() {
+    return toFixedHex(this.pubkey) + toFixedHex(this.encryptionKey).slice(2)
+  }
+
+  static fromString(str) {
+    if (str.length === 130) {
+      str = str.slice(2)
+    }
+    if (str.length !== 128) {
+      throw new Error('Invalid key length')
+    }
+    return Object.assign(new Keypair(), {
+      privkey: null,
+      pubkey: BigNumber.from('0x' + str.slice(0, 64)),
+      encryptionKey: BigNumber.from('0x' + str.slice(64, 128)),
+    })
+  }
+}
+
+module.exports = Keypair
diff --git a/src/utxo.js b/src/utxo.js
index 47f2f45..6a60da1 100644
--- a/src/utxo.js
+++ b/src/utxo.js
@@ -1,43 +1,29 @@
 const { ethers } = require('hardhat')
 const { BigNumber } = ethers
 const { randomBN, poseidonHash } = require('./utils')
-
-function fromPrivkey(privkey) {
-  return {
-    privkey,
-    pubkey: poseidonHash([privkey]),
-  }
-}
+const Keypair = require('./kaypair')
 
 class Utxo {
-  constructor({ amount, pubkey, privkey, blinding, index } = {}) {
-    if (!pubkey) {
-      if (privkey) {
-        pubkey = fromPrivkey(privkey).pubkey
-      } else {
-        ;({ pubkey, privkey } = fromPrivkey(randomBN()))
-      }
-    }
-    this.amount = BigNumber.from(amount || 0)
-    this.blinding = blinding || randomBN()
-    this.pubkey = pubkey
-    this.privkey = privkey
+  constructor({ amount = 0, keypair = new Keypair(), blinding = randomBN(), index } = {}) {
+    this.amount = BigNumber.from(amount)
+    this.blinding = BigNumber.from(blinding)
+    this.keypair = keypair
     this.index = index
   }
 
   getCommitment() {
     if (!this._commitment) {
-      this._commitment = poseidonHash([this.amount, this.blinding, this.pubkey])
+      this._commitment = poseidonHash([this.amount, this.blinding, this.keypair.pubkey])
     }
     return this._commitment
   }
 
   getNullifier() {
     if (!this._nullifier) {
-      if (this.amount > 0 && (this.index === undefined || !this.privkey === undefined)) {
+      if (this.amount > 0 && (this.index === undefined || this.keypair.privkey === undefined || this.keypair.privkey === null)) {
         throw new Error('Can not compute nullifier without utxo index or private key')
       }
-      this._nullifier = poseidonHash([this.getCommitment(), this.index || 0, this.privkey || 0])
+      this._nullifier = poseidonHash([this.getCommitment(), this.index || 0, this.keypair.privkey || 0])
     }
     return this._nullifier
   }