# Smart Contract

## `constructor()`

```solidity
constructor(address _publicKey, uint256 _cluID) {
        publicKey = _publicKey;
        cluID = _cluID;
}
```

The `_publicKey` that you need to put if you are using our public backend service is **`0xd1309C93a4bF7C7a1eE81E5fC8291Adb583cc602`** and the **`cluID`** is **`0`**

## `useclu3()`

```solidity
function useclu3(uint256 _timestamp, bytes memory signature) public returns(bool) {
        bytes32 message = keccak256(abi.encodePacked(msg.sender, _timestamp, cluID));
        if(recoverSigner(message, signature) == publicKey) {
            if(checkStorage(Strings.toString(_timestamp))){
                return true;
            } else {
                revert("timestamp + cluID already used");
            }
        }
        revert("Invalid signature");
}
```

The arguments that needs to be passed are the **`_timestamp`** and the **`signature of the message`** returned by the backend service.


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