From 397942f94db7f2affd7807832b620c659ce711df Mon Sep 17 00:00:00 2001
From: poma <semenov.roma@gmail.com>
Date: Sat, 30 Oct 2021 20:14:47 +0100
Subject: [PATCH] reorder blinding, pubkey, amount

---
 circuits/transaction.circom | 22 +++++++++++-----------
 src/utxo.js                 |  8 ++++----
 2 files changed, 15 insertions(+), 15 deletions(-)

diff --git a/circuits/transaction.circom b/circuits/transaction.circom
index 0887d50..856d361 100644
--- a/circuits/transaction.circom
+++ b/circuits/transaction.circom
@@ -6,12 +6,12 @@ include "./keypair.circom"
 Utxo structure:
 {
     amount,
-    blinding, // random number
     pubkey,
+    blinding, // random number
 }
 
-commitment = hash(amount, blinding, pubKey)
-nullifier = hash(commitment, privKey, merklePath)
+commitment = hash(amount, pubKey, blinding)
+nullifier = hash(commitment, merklePath, privKey)
 */
 
 // Universal JoinSplit transaction with nIns inputs and 2 outputs
@@ -26,16 +26,16 @@ template Transaction(levels, nIns, nOuts, zeroLeaf) {
     // data for transaction inputs
     signal         input inputNullifier[nIns];
     signal private input inAmount[nIns];
-    signal private input inBlinding[nIns];
     signal private input inPrivateKey[nIns];
+    signal private input inBlinding[nIns];
     signal private input inPathIndices[nIns];
     signal private input inPathElements[nIns][levels];
 
     // data for transaction outputs
     signal         input outputCommitment[nOuts];
     signal private input outAmount[nOuts];
-    signal private input outBlinding[nOuts];
     signal private input outPubkey[nOuts];
+    signal private input outBlinding[nOuts];
 
     component inKeypair[nIns];
     component inUtxoHasher[nIns];
@@ -51,8 +51,8 @@ template Transaction(levels, nIns, nOuts, zeroLeaf) {
 
         inUtxoHasher[tx] = Poseidon(3);
         inUtxoHasher[tx].inputs[0] <== inAmount[tx];
-        inUtxoHasher[tx].inputs[1] <== inBlinding[tx];
-        inUtxoHasher[tx].inputs[2] <== inKeypair[tx].publicKey;
+        inUtxoHasher[tx].inputs[1] <== inKeypair[tx].publicKey;
+        inUtxoHasher[tx].inputs[2] <== inBlinding[tx];
 
         nullifierHasher[tx] = Poseidon(3);
         nullifierHasher[tx].inputs[0] <== inUtxoHasher[tx].out;
@@ -73,8 +73,8 @@ template Transaction(levels, nIns, nOuts, zeroLeaf) {
         checkRoot[tx].in[1] <== tree[tx].root;
         checkRoot[tx].enabled <== inAmount[tx];
 
-        // We don't need to range check input amounts, since all inputs are valid UTXOs that 
-        // were already checked as outputs in the previous transaction (or zero amount UTXOs that don't 
+        // We don't need to range check input amounts, since all inputs are valid UTXOs that
+        // were already checked as outputs in the previous transaction (or zero amount UTXOs that don't
         // need to be checked either).
 
         sumIns += inAmount[tx];
@@ -88,8 +88,8 @@ template Transaction(levels, nIns, nOuts, zeroLeaf) {
     for (var tx = 0; tx < nOuts; tx++) {
         outUtxoHasher[tx] = Poseidon(3);
         outUtxoHasher[tx].inputs[0] <== outAmount[tx];
-        outUtxoHasher[tx].inputs[1] <== outBlinding[tx];
-        outUtxoHasher[tx].inputs[2] <== outPubkey[tx];
+        outUtxoHasher[tx].inputs[1] <== outPubkey[tx];
+        outUtxoHasher[tx].inputs[2] <== outBlinding[tx];
         outUtxoHasher[tx].out === outputCommitment[tx];
 
         // Check that amount fits into 248 bits to prevent overflow
diff --git a/src/utxo.js b/src/utxo.js
index 5a9b192..65dd420 100644
--- a/src/utxo.js
+++ b/src/utxo.js
@@ -25,7 +25,7 @@ class Utxo {
    */
   getCommitment() {
     if (!this._commitment) {
-      this._commitment = poseidonHash([this.amount, this.blinding, this.keypair.pubkey])
+      this._commitment = poseidonHash([this.amount, this.keypair.pubkey, this.blinding])
     }
     return this._commitment
   }
@@ -57,7 +57,7 @@ class Utxo {
    * @returns {string} `0x`-prefixed hex string with data
    */
   encrypt() {
-    const bytes = Buffer.concat([toBuffer(this.blinding, 31), toBuffer(this.amount, 31)])
+    const bytes = Buffer.concat([toBuffer(this.amount, 31), toBuffer(this.blinding, 31)])
     return this.keypair.encrypt(bytes)
   }
 
@@ -72,8 +72,8 @@ class Utxo {
   static decrypt(keypair, data, index) {
     const buf = keypair.decrypt(data)
     return new Utxo({
-      blinding: BigNumber.from('0x' + buf.slice(0, 31).toString('hex')),
-      amount: BigNumber.from('0x' + buf.slice(31, 62).toString('hex')),
+      amount: BigNumber.from('0x' + buf.slice(0, 31).toString('hex')),
+      blinding: BigNumber.from('0x' + buf.slice(31, 62).toString('hex')),
       keypair,
       index,
     })