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