Bitcoin implemented as a token smart contract on Ethereum.
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Latest commit 129c771 Mar 20, 2018


Deployed on Ethereum


An ERC20 token that is mined using PoW through a SmartContract

  • No pre-mine
  • No ICO
  • 21,000,000 tokens total
  • Difficulty target auto-adjusts with PoW hashrate
  • Rewards decrease as more tokens are minted
  • Compatible with all services that support ERC20 tokens

How does it work?

Typically, ERC20 tokens will grant all tokens to the owner or will have an ICO and demand that large amounts of Ether be sent to the owner. Instead of granting tokens to the 'contract owner', all 0xbitcoin tokens are locked within the smart contract initially. These tokens are dispensed, 50 at a time, by calling the function 'mint' and using Proof of Work, just like mining bitcoin. Here is what that looks like:

 function mint(uint256 nonce, bytes32 challenge_digest) public returns (bool success) {

    uint reward_amount = getMiningReward();

    bytes32 digest =  keccak256(challengeNumber, msg.sender, nonce );

    if (digest != challenge_digest) revert();

    //the digest must be smaller than the target
    if(uint256(digest) > miningTarget) revert();

     uint hashFound = rewardHashesFound[digest];
     rewardHashesFound[digest] = epochCount;
     if(hashFound != 0) revert();  //prevent the same answer from awarding twice

    balances[msg.sender] = balances[msg.sender].add(reward_amount);

    tokensMinted = tokensMinted.add(reward_amount);

    //set readonly diagnostics data
    lastRewardTo = msg.sender;
    lastRewardAmount = reward_amount;
    lastRewardEthBlockNumber = block.number;
    //start a new round of mining with a new 'challengeNumber'

      Mint(msg.sender, reward_amount, epochCount, challengeNumber );

   return true;


As you can see, a special number called a 'nonce' has to be passed into this function in order for tokens to be dispensed. This number has to fit a special 'puzzle' similar to a sudoku puzzle, and this is called Proof of Work. To find this special number, it is necessary to run a mining program. A cpu miner exists for mining 0xbitcoin tokens and it can be downloaded here:

Transfer ERC20 Tokens


Deployed on Ropsten: 0x9D2Cc383E677292ed87f63586086CfF62a009010

npm install -g ethereumjs-testrpc ( testrpc

truffle test