solidity.md

Blackbox Coding Challenge: Hack The Token Contract

Problem Description

You've been given the below token smart contract. Your goal is to identify the vulnerabilities and hack the contract to get more tokens.

Submission Instructions:

Once completed, please create a new repository called "Blackbox Hack The Token Contract" under your personal github account. Then email your interviewer a link to the new repo.

Submission Requirements

You should submit a revised contract and a brief explanation (2-3 sentences) of the vulnerability and your plan of action

You may write your program in any of the following languages:

• Solidity (0.4+)

Token Smart Contract

  pragma solidity ^0.4.23;

  contract Token {

    mapping(address => uint) balances;
    uint public totalSupply;

    function Token(uint _initialSupply) public {
      balances[msg.sender] = totalSupply = _initialSupply;
    }

    function transfer(address _to, uint _value) public returns (bool) {
      require(balances[msg.sender] - _value >= 0);
      balances[msg.sender] -= _value;
      balances[_to] += _value;
      return true;
    }

    function balanceOf(address _owner) public view returns (uint balance) {
      return balances[_owner];
    }
  }