想请教一个 solidity 以太坊合约的代码问题

pragma solidity ^0.4.23; contract Preservation { // public library contracts address public timeZone1Library; address public timeZone2Library; address public owner; uint storedTime; // Sets the function signature for delegatecall bytes4 constant setTimeSignature = bytes4(keccak256("setTime(uint256)")); event FLAG(string b64email, string slogan); constructor(address _timeZone1LibraryAddress, address _timeZone2LibraryAddress) public { timeZone1Library = _timeZone1LibraryAddress; timeZone2Library = _timeZone2LibraryAddress; owner = msg.sender; } // set the time for timezone 1 function setFirstTime(uint _timeStamp) public { timeZone1Library.delegatecall(setTimeSignature, _timeStamp); } // set the time for timezone 2 function setSecondTime(uint _timeStamp) public { timeZone2Library.delegatecall(setTimeSignature, _timeStamp); } function CaptureTheFlag(string b64email) public{ require (owner == msg.sender); emit FLAG(b64email, "Congratulations to capture the flag!"); } } // Simple library contract to set the time contract LibraryContract { // stores a timestamp uint storedTime; function setTime(uint _time) public { storedTime = _time; } } 

对以太坊相关一窍不通，看了不少文章还是有点摸不着头脑....

这是区块链安全想关的，想请教一下这段合约代码放在 Remix 上编译运行后调用CaptureTheFlag函数前有什么约束吗（这里的目的是调用该函数），我的猜想这里时间戳可能与uint256溢出有关