1. 题目 I created a token bank. It allows anyone to deposit tokens by transferring them to the bank and then to withdraw those tokens later. It uses ERC 223 to accept the incoming tokens. The bank de...

1. 题目 To complete this challenge, become the owner 源码 12345678910111213141516pragma solidity ^0.4.21;contract AssumeOwnershipChallenge { address owner; bool public isComplete; functi...

1. 题目 To complete this challenge, send a transaction from the owner‘s account. 源码 123456789101112pragma solidity ^0.4.21;contract AccountTakeoverChallenge { address owner = 0x6B477781b0e68...

Public Key1. 题目 Recall that an address is the last 20 bytes of the keccak-256 hash of the address’s public key. To complete this challenge, find the public key for the owner‘s account. 源码 12345678...

Fuzzy identity1. 题目 1.1 This contract can only be used by me (smarx). I don’t trust myself to remember my private key, so I’ve made it so whatever address I’m using in the future will work: I al...

Fifty years1. 题目 1.1 This contract locks away ether. The initial ether is locked away until 50 years has passed, and subsequent contributions are locked until even later. All you have to do to com...

Donation1. 题目 1.1 A candidate you don’t like is accepting campaign contributions via the smart contract below. To complete this challenge, steal the candidate’s ether. 1.2 源码： 12345678910111213...

Mapping1. 题目 1.1 Who needs mappings? I’ve created a contract that can store key/value pairs using just an array. 1.2 源码： 12345678910111213141516171819pragma solidity ^0.4.21;contract MappingC...

Retirement fund1. 题目 1.1 This retirement fund is what economists call a commitment device. I’m trying to make sure I hold on to 1 ether for retirement. I’ve committed 1 ether to the contract belo...

Token whale1. 题目 1.1 要求： This ERC20-compatible token is hard to acquire. There’s a fixed supply of 1,000 tokens, all of which are yours to start with. Find a way to accumulate at least 1,000,000 t...