0

The token .sol:

// ----------------------------------------------------------------------------
// '0xBitcoin Token' contract
// Mineable ERC20 Token using Proof Of Work
//
// Symbol      : 0xBTC
// Name        : 0xBitcoin Token
// Total supply: 21,000,000.00
// Decimals    : 8
//
// ----------------------------------------------------------------------------

// ----------------------------------------------------------------------------
// Safe maths
// ----------------------------------------------------------------------------

library SafeMath {
    function add(uint a, uint b) internal pure returns (uint c) {
        c = a + b;
        require(c >= a);
    }

    function sub(uint a, uint b) internal pure returns (uint c) {
        require(b <= a);
        c = a - b;
    }

    function mul(uint a, uint b) internal pure returns (uint c) {
        c = a * b;
        require(a == 0 || c / a == b);
    }

    function div(uint a, uint b) internal pure returns (uint c) {
        require(b > 0);
        c = a / b;
    }
}

library ExtendedMath {
    //return the smaller of the two inputs (a or b)
    function limitLessThan(uint a, uint b) internal pure returns (uint c) {
        if(a > b) return b;
        return a;
    }
}

// ----------------------------------------------------------------------------
// ERC Token Standard #20 Interface
// https://github.com/ethereum/EIPs/blob/master/EIPS/eip-20-token-standard.md
// ----------------------------------------------------------------------------

contract ERC20Interface {
    function totalSupply() public constant returns (uint);
    function balanceOf(address tokenOwner) public constant returns (uint balance);
    function allowance(address tokenOwner, address spender) public constant returns (uint remaining);
    function transfer(address to, uint tokens) public returns (bool success);
    function approve(address spender, uint tokens) public returns (bool success);
    function transferFrom(address from, address to, uint tokens) public returns (bool success);

    event Transfer(address indexed from, address indexed to, uint tokens);
    event Approval(address indexed tokenOwner, address indexed spender, uint tokens);
}

// ----------------------------------------------------------------------------
// Contract function to receive approval and execute function in one call
//
// Borrowed from MiniMeToken
// ----------------------------------------------------------------------------

contract ApproveAndCallFallBack {
    function receiveApproval(address from, uint256 tokens, address token, bytes data) public;
}

// ----------------------------------------------------------------------------
// Owned contract
// ----------------------------------------------------------------------------

contract Owned {
    address public owner;
    address public newOwner;

    event OwnershipTransferred(address indexed _from, address indexed _to);

    function Owned() public {
        owner = msg.sender;
    }

    modifier onlyOwner {
        require(msg.sender == owner);
        _;
    }

    function transferOwnership(address _newOwner) public onlyOwner {
        newOwner = _newOwner;
    }

    function acceptOwnership() public {
        require(msg.sender == newOwner);
        OwnershipTransferred(owner, newOwner);
        owner = newOwner;
        newOwner = address(0);
    }
}

// ----------------------------------------------------------------------------
// ERC20 Token, with the addition of symbol, name and decimals and an
// initial fixed supply
// ----------------------------------------------------------------------------

contract _0xBitcoinToken is ERC20Interface, Owned {
    using SafeMath for uint;
    using ExtendedMath for uint;

    string public symbol;
    string public  name;
    uint8 public decimals;
    uint public _totalSupply;
    uint public latestDifficultyPeriodStarted;
    uint public epochCount;//number of 'blocks' mined
    uint public _BLOCKS_PER_READJUSTMENT = 1024;

    //a little number
    uint public  _MINIMUM_TARGET = 2**16;
    //a big number is easier ; just find a solution that is smaller
    //uint public  _MAXIMUM_TARGET = 2**224;  bitcoin uses 224
    uint public  _MAXIMUM_TARGET = 2**234;
    uint public miningTarget;
    bytes32 public challengeNumber;   //generate a new one when a new reward is minted

    uint public rewardEra;
    uint public maxSupplyForEra;

    address public lastRewardTo;
    uint public lastRewardAmount;
    uint public lastRewardEthBlockNumber;
    bool locked = false;
    mapping(bytes32 => bytes32) solutionForChallenge;
    uint public tokensMinted;
    mapping(address => uint) balances;
    mapping(address => mapping(address => uint)) allowed;

    event Mint(address indexed from, uint reward_amount, uint epochCount, bytes32 newChallengeNumber);

    // ------------------------------------------------------------------------
    // Constructor
    // ------------------------------------------------------------------------

    function _0xBitcoinToken() public onlyOwner{
        symbol = "0xBTC";
        name = "0xBitcoin Token";
        decimals = 8;
        _totalSupply = 21000000 * 10**uint(decimals);

        if(locked) revert();

        locked = true;
        tokensMinted = 0;
        rewardEra = 0;
        maxSupplyForEra = _totalSupply.div(2);
        miningTarget = _MAXIMUM_TARGET;

        latestDifficultyPeriodStarted = block.number;
        _startNewMiningEpoch();

        //The owner gets nothing! You must mine this ERC20 token
        //balances[owner] = _totalSupply;
        //Transfer(address(0), owner, _totalSupply);
    }

    function mint(uint256 nonce, bytes32 challenge_digest) public returns (bool success) {
        // the PoW must contain work that includes a recent ethereum block hash (challenge number) and the msg.sender's address to prevent MITM attacks
        bytes32 digest =  keccak256(challengeNumber, msg.sender, nonce );

        // the challenge digest must match the expected
        if (digest != challenge_digest) revert();

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

        // only allow one reward for each challenge
         bytes32 solution = solutionForChallenge[challengeNumber];
         solutionForChallenge[challengeNumber] = digest;
         if(solution != 0x0) revert();  //prevent the same answer from awarding twice
        uint reward_amount = getMiningReward();
        balances[msg.sender] = balances[msg.sender].add(reward_amount);
        tokensMinted = tokensMinted.add(reward_amount);

        // Cannot mint more tokens than there are
        assert(tokensMinted <= maxSupplyForEra);

        // set readonly diagnostics data
        lastRewardTo = msg.sender;
        lastRewardAmount = reward_amount;
        lastRewardEthBlockNumber = block.number;

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

        return true;
    }

    // a new 'block' to be mined
    function _startNewMiningEpoch() internal {
        // if max supply for the era will be exceeded next reward round then enter the new era before that happens
        // 40 is the final reward era, almost all tokens minted
        // once the final era is reached, more tokens will not be given out because the assert function
        if (tokensMinted.add(getMiningReward()) > maxSupplyForEra && rewardEra < 39) {
            rewardEra = rewardEra + 1;
        }

        // set the next minted supply at which the era will change
        // total supply is 2100000000000000  because of 8 decimal places
        maxSupplyForEra = _totalSupply - _totalSupply.div( 2**(rewardEra + 1));
        epochCount = epochCount.add(1);

        // every so often, readjust difficulty. Dont readjust when deploying
        if (epochCount % _BLOCKS_PER_READJUSTMENT == 0) {
            _reAdjustDifficulty();
        }

        // make the latest ethereum block hash a part of the next challenge for PoW to prevent pre-mining future blocks
        // do this last since this is a protection mechanism in the mint() function
        challengeNumber = block.blockhash(block.number - 1);
    }

    // https://en.bitcoin.it/wiki/Difficulty#What_is_the_formula_for_difficulty.3F
    // as of 2017 the bitcoin difficulty was up to 17 zeroes, it was only 8 in the early days
    // readjust the target by 5 percent
    function _reAdjustDifficulty() internal {
        uint ethBlocksSinceLastDifficultyPeriod = block.number - latestDifficultyPeriodStarted;
        // assume 360 ethereum blocks per hour
        // we want miners to spend 10 minutes to mine each 'block', about 60 ethereum blocks = one 0xbitcoin epoch
        uint epochsMined = _BLOCKS_PER_READJUSTMENT; //256
        uint targetEthBlocksPerDiffPeriod = epochsMined * 60; //should be 60 times slower than ethereum

        // if there were less eth blocks passed in time than expected
        if (ethBlocksSinceLastDifficultyPeriod < targetEthBlocksPerDiffPeriod ) {
            uint excess_block_pct = (targetEthBlocksPerDiffPeriod.mul(100)).div( ethBlocksSinceLastDifficultyPeriod );

            uint excess_block_pct_extra = excess_block_pct.sub(100).limitLessThan(1000);
            // If there were 5% more blocks mined than expected then this is 5.  If there were 100% more blocks mined than expected then this is 100.

            // make it harder
            miningTarget = miningTarget.sub(miningTarget.div(2000).mul(excess_block_pct_extra));   //by up to 50 %
        } else {
            uint shortage_block_pct = (ethBlocksSinceLastDifficultyPeriod.mul(100)).div( targetEthBlocksPerDiffPeriod );
            uint shortage_block_pct_extra = shortage_block_pct.sub(100).limitLessThan(1000); //always between 0 and 1000

            // make it easier
            miningTarget = miningTarget.add(miningTarget.div(2000).mul(shortage_block_pct_extra));   //by up to 50 %
        }

        latestDifficultyPeriodStarted = block.number;

        if(miningTarget < _MINIMUM_TARGET) { // very difficult
            miningTarget = _MINIMUM_TARGET;
        }

        if(miningTarget > _MAXIMUM_TARGET) { // very easy
            miningTarget = _MAXIMUM_TARGET;
        }
    }


    // this is a recent ethereum block hash, used to prevent pre-mining future blocks
    function getChallengeNumber() public constant returns (bytes32) {
        return challengeNumber;
    }

    // the number of zeroes the digest of the PoW solution requires.  Auto adjusts
    function getMiningDifficulty() public constant returns (uint) {
        return _MAXIMUM_TARGET.div(miningTarget);
    }

    function getMiningTarget() public constant returns (uint) {
       return miningTarget;
    }

    // 21m coins total
    // reward begins at 50 and is cut in half every reward era (as tokens are mined)
    function getMiningReward() public constant returns (uint) {
        // once we get half way thru the coins, only get 25 per block
        // every reward era, the reward amount halves.
        return (50 * 10**uint(decimals) ).div( 2**rewardEra ) ;
    }

    // help debug mining software
    function getMintDigest(uint256 nonce, bytes32 challenge_digest, bytes32 challenge_number) public view returns (bytes32 digesttest) {
        bytes32 digest = keccak256(challenge_number,msg.sender,nonce);
        return digest;
    }

    // help debug mining software
    function checkMintSolution(uint256 nonce, bytes32 challenge_digest, bytes32 challenge_number, uint testTarget) public view returns (bool success) {
        bytes32 digest = keccak256(challenge_number,msg.sender,nonce);
        if(uint256(digest) > testTarget) revert();
        return (digest == challenge_digest);
    }

    // ------------------------------------------------------------------------
    // Total supply
    // ------------------------------------------------------------------------
    function totalSupply() public constant returns (uint) {
        return _totalSupply  - balances[address(0)];
    }

    // ------------------------------------------------------------------------
    // Get the token balance for account `tokenOwner`
    // ------------------------------------------------------------------------
    function balanceOf(address tokenOwner) public constant returns (uint balance) {
        return balances[tokenOwner];
    }

    // ------------------------------------------------------------------------
    // Transfer the balance from token owner's account to `to` account
    // - Owner's account must have sufficient balance to transfer
    // - 0 value transfers are allowed
    // ------------------------------------------------------------------------

    function transfer(address to, uint tokens) public returns (bool success) {
        balances[msg.sender] = balances[msg.sender].sub(tokens);
        balances[to] = balances[to].add(tokens);
        Transfer(msg.sender, to, tokens);
        return true;
    }

    // ------------------------------------------------------------------------
    // Token owner can approve for `spender` to transferFrom(...) `tokens`
    // from the token owner's account
    //
    // https://github.com/ethereum/EIPs/blob/master/EIPS/eip-20-token-standard.md
    // recommends that there are no checks for the approval double-spend attack
    // as this should be implemented in user interfaces
    // ------------------------------------------------------------------------
    function approve(address spender, uint tokens) public returns (bool success) {
        allowed[msg.sender][spender] = tokens;
        Approval(msg.sender, spender, tokens);
        return true;
    }

    // ------------------------------------------------------------------------
    // Transfer `tokens` from the `from` account to the `to` account
    //
    // The calling account must already have sufficient tokens approve(...)-d
    // for spending from the `from` account and
    // - From account must have sufficient balance to transfer
    // - Spender must have sufficient allowance to transfer
    // - 0 value transfers are allowed
    // ------------------------------------------------------------------------
    function transferFrom(address from, address to, uint tokens) public returns (bool success) {
        balances[from] = balances[from].sub(tokens);
        allowed[from][msg.sender] = allowed[from][msg.sender].sub(tokens);
        balances[to] = balances[to].add(tokens);
        Transfer(from, to, tokens);
        return true;
    }

    // ------------------------------------------------------------------------
    // Returns the amount of tokens approved by the owner that can be
    // transferred to the spender's account
    // ------------------------------------------------------------------------
    function allowance(address tokenOwner, address spender) public constant returns (uint remaining) {
        return allowed[tokenOwner][spender];
    }

    // ------------------------------------------------------------------------
    // Token owner can approve for `spender` to transferFrom(...) `tokens`
    // from the token owner's account. The `spender` contract function
    // `receiveApproval(...)` is then executed
    // ------------------------------------------------------------------------
    function approveAndCall(address spender, uint tokens, bytes data) public returns (bool success) {
        allowed[msg.sender][spender] = tokens;
        Approval(msg.sender, spender, tokens);
        ApproveAndCallFallBack(spender).receiveApproval(msg.sender, tokens, this, data);
        return true;
    }

    // ------------------------------------------------------------------------
    // Don't accept ETH
    // ------------------------------------------------------------------------
    function () public payable {
        revert();
    }

    // ------------------------------------------------------------------------
    // Owner can transfer out any accidentally sent ERC20 tokens
    // ------------------------------------------------------------------------
    function transferAnyERC20Token(address tokenAddress, uint tokens) public onlyOwner returns (bool success) {
        return ERC20Interface(tokenAddress).transfer(owner, tokens);
    }
}
0

After running truffle migrate, the contract address will be displayed in the console window you migrated. Alternatively, you can look in the produced JSONs and it will be towards the end under "networks", [networkId], "address".

"networks": { "1": { "events": {}, "links": {}, "address": "0x6e017d0c76884f524ed6bc84edfdac40195e582a", "transactionHash": "0x76867325534065bb9787b81e19ecd90d52f639a7113b22483bf599177f9c02af" } },

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.