remove commitment from signature

circuits/keypair.circom

@@ -12,13 +12,11 @@ template Keypair() {
 
 template Signature() {
     signal input privateKey;
-    signal input commitment;
     signal input merklePath;
     signal output out;
 
-    component hasher = Poseidon(3);
+    component hasher = Poseidon(2);
     hasher.inputs[0] <== privateKey;
-    hasher.inputs[1] <== commitment;
-    hasher.inputs[2] <== merklePath;
+    hasher.inputs[1] <== merklePath;
     out <== hasher.out;
 }

circuits/transaction.circom

@@ -11,7 +11,7 @@ Utxo structure:
 }
 
 commitment = hash(amount, pubKey, blinding)
-nullifier = hash(commitment, merklePath, sign(commitment + merklePath, privKey))
+nullifier = hash(commitment, merklePath, sign(merklePath, privKey))
 */
 
 // Universal JoinSplit transaction with nIns inputs and 2 outputs
@@ -57,7 +57,6 @@ template Transaction(levels, nIns, nOuts, zeroLeaf) {
 
         inSignature[tx] = Signature();
         inSignature[tx].privateKey <== inPrivateKey[tx];
-        inSignature[tx].commitment <== inUtxoHasher[tx].out;
         inSignature[tx].merklePath <== inPathIndices[tx];
 
         nullifierHasher[tx] = Poseidon(3);

src/keypair.js

@@ -85,8 +85,8 @@ class Keypair {
    * @param {string|number|BigNumber} merklePath a hex string with merkle path
    * @returns {BigNumber} a hex string with signature
    */
-  sign(commitment, merklePath) {
-    return poseidonHash([this.privkey, commitment, merklePath])
+  sign(merklePath) {
+    return poseidonHash([this.privkey, merklePath])
   }
 
   /**

src/utxo.js

@@ -46,7 +46,7 @@ class Utxo {
       ) {
         throw new Error('Can not compute nullifier without utxo index or private key')
       }
-      const signature = this.keypair.privkey ? this.keypair.sign(this.getCommitment(), this.index || 0) : 0
+      const signature = this.keypair.privkey ? this.keypair.sign(this.index || 0) : 0
       this._nullifier = poseidonHash([this.getCommitment(), this.index || 0, signature])
     }
     return this._nullifier