From 45705daf1d691f42f2238688e85731ebd0f50964 Mon Sep 17 00:00:00 2001
From: Andriian Chestnykh <>
Date: Thu, 4 Apr 2024 16:00:34 +0100
Subject: [PATCH 1/2] Remove unnecessary hook

---
 contracts/examples/ERC20Verifier.sol | 13 -------------
 1 file changed, 13 deletions(-)

diff --git a/contracts/examples/ERC20Verifier.sol b/contracts/examples/ERC20Verifier.sol
index 1166862..bacb7fc 100644
--- a/contracts/examples/ERC20Verifier.sol
+++ b/contracts/examples/ERC20Verifier.sol
@@ -44,19 +44,6 @@ contract ERC20Verifier is ERC20Upgradeable, ZKPVerifier {
         $.TOKEN_AMOUNT_FOR_AIRDROP_PER_ID = 5 * 10 ** uint256(decimals());
     }
 
-    function _beforeProofSubmit(
-        uint64 /* requestId */,
-        uint256[] memory inputs,
-        ICircuitValidator validator
-    ) internal view override {
-        // check that challenge input is address of sender
-        address addr = PrimitiveTypeUtils.uint256LEToAddress(
-            inputs[validator.inputIndexOf('challenge')]
-        );
-        // this is linking between msg.sender and
-        require(_msgSender() == addr, 'address in proof is not a sender address');
-    }
-
     function _afterProofSubmit(
         uint64 requestId,
         uint256[] memory inputs,

From 92136f2f30ee4d246ddf8ce3ef2ef42a6287d13b Mon Sep 17 00:00:00 2001
From: Andriian Chestnykh <>
Date: Fri, 5 Apr 2024 07:11:09 +0100
Subject: [PATCH 2/2] Add one time minting restriction to
 ERC20LinkedUniversalVerifier.sol

---
 contracts/examples/ERC20LinkedUniversalVerifier.sol   | 11 ++++++++++-
 .../erc20-with-universal-verifier.ts                  |  2 +-
 2 files changed, 11 insertions(+), 2 deletions(-)

diff --git a/contracts/examples/ERC20LinkedUniversalVerifier.sol b/contracts/examples/ERC20LinkedUniversalVerifier.sol
index a6ec1cd..73469e8 100644
--- a/contracts/examples/ERC20LinkedUniversalVerifier.sol
+++ b/contracts/examples/ERC20LinkedUniversalVerifier.sol
@@ -12,6 +12,8 @@ contract ERC20LinkedUniversalVerifier is ERC20 {
     uint64 public constant TRANSFER_REQUEST_ID_MTP_VALIDATOR = 1;
 
     UniversalVerifier public verifier;
+    mapping(uint256 => address) public idToAddress;
+    mapping(address => uint256) public addressToId;
 
     uint256 public TOKEN_AMOUNT_FOR_AIRDROP_PER_ID = 5 * 10 ** uint256(decimals());
 
@@ -33,7 +35,14 @@ contract ERC20LinkedUniversalVerifier is ERC20 {
     }
 
     function mint(address to) public {
-        _mint(to, TOKEN_AMOUNT_FOR_AIRDROP_PER_ID);
+        uint256 id = verifier.getProofStorageField(to, TRANSFER_REQUEST_ID_SIG_VALIDATOR, "userID");
+        id = id == 0 ? verifier.getProofStorageField(to, TRANSFER_REQUEST_ID_MTP_VALIDATOR, "userID") : id;
+
+        if (idToAddress[id] == address(0) && addressToId[to] == 0) {
+            idToAddress[id] = to;
+            addressToId[to] = id;
+            _mint(to, TOKEN_AMOUNT_FOR_AIRDROP_PER_ID);
+        }
     }
 
     function _update(
diff --git a/test/validators/universal-verifier/erc20-with-universal-verifier.ts b/test/validators/universal-verifier/erc20-with-universal-verifier.ts
index b586d50..d01c2cd 100644
--- a/test/validators/universal-verifier/erc20-with-universal-verifier.ts
+++ b/test/validators/universal-verifier/erc20-with-universal-verifier.ts
@@ -33,7 +33,7 @@ describe('ERC 20 test', function () {
   let state: any, sig: any, mtp: any;
   let universalVerifier: Contract, erc20LinkedUniversalVerifier: Contract;
 
-  before(async () => {
+  beforeEach(async () => {
     const contractsSig = await deployValidatorContracts(
       'VerifierSigWrapper',
       'CredentialAtomicQuerySigV2Validator'