From a533ad9ffb62163a42d4fa9a09984c5dd4e5c41d Mon Sep 17 00:00:00 2001
From: Alexey <peretsmobil@gmail.com>
Date: Tue, 28 Apr 2020 10:36:48 +0300
Subject: [PATCH] Add explicit constrains for recepient, relayer and fee

---
 circuits/withdraw.circom | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/circuits/withdraw.circom b/circuits/withdraw.circom
index bed8cd6..54c3838 100644
--- a/circuits/withdraw.circom
+++ b/circuits/withdraw.circom
@@ -50,6 +50,18 @@ template Withdraw(levels) {
         tree.pathElements[i] <== pathElements[i];
         tree.pathIndices[i] <== pathIndices[i];
     }
+
+    // Add hidden signals to make sure that tampering with recipient or fee will invalidate the snark proof
+    // Most likely it is not required, but it's better to stay on the safe side and it only takes 2 constraints
+    // Squares are used to prevent optimizer from removing those constraints
+    signal recipientSquare;
+    signal feeSquare;
+    signal relayerSquare;
+    signal refundSquare;
+    recipientSquare <== recipient * recipient;
+    feeSquare <== fee * fee;
+    relayerSquare <== relayer * relayer;
+    refundSquare <== refund * refund;
 }
 
 component main = Withdraw(20);