pragma solidity ^0.4.17;

/**
 * @title SafeMath
 * @dev Math operations with safety checks that throw on error
 */
library SafeMath {
    function mul(uint256 a, uint256 b) internal pure returns (uint256) {
        if (a == 0) {
            return 0;
        }
        uint256 c = a * b;
        assert(c / a == b);
        return c;
    }

    function div(uint256 a, uint256 b) internal pure returns (uint256) {
        // assert(b > 0); // Solidity automatically throws when dividing by 0
        uint256 c = a / b;
        // assert(a == b * c + a % b); // There is no case in which this doesn't hold
        return c;
    }

    function sub(uint256 a, uint256 b) internal pure returns (uint256) {
        assert(b <= a);
        return a - b;
    }

    function add(uint256 a, uint256 b) internal pure returns (uint256) {
        uint256 c = a + b;
        assert(c >= a);
        return c;
    }
}

/**
 * @title Ownable
 * @dev The Ownable contract has an owner address, and provides basic authorization control
 * functions, this simplifies the implementation of "user permissions".
 */
contract Ownable {
    address public owner;

    /**
      * @dev The Ownable constructor sets the original `owner` of the contract to the sender
      * account.
      */
    function Ownable() public {
        owner = msg.sender;
    }

    /**
      * @dev Throws if called by any account other than the owner.
      */
    modifier onlyOwner() {
        require(msg.sender == owner);
        _;
    }

    /**
    * @dev Allows the current owner to transfer control of the contract to a newOwner.
    * @param newOwner The address to transfer ownership to.
    */
    function transferOwnership(address newOwner) public onlyOwner {
        if (newOwner != address(0)) {
            owner = newOwner;
        }
    }

}

/**
 * @title ERC20Basic
 * @dev Simpler version of ERC20 interface
 * @dev see https://github.com/ethereum/EIPs/issues/20
 */
contract ERC20Basic {
    uint public _totalSupply;
    function totalSupply() public constant returns (uint);
    function balanceOf(address who) public constant returns (uint);
    function transfer(address to, uint value) public;
    event Transfer(address indexed from, address indexed to, uint value);
}

/**
 * @title ERC20 interface
 * @dev see https://github.com/ethereum/EIPs/issues/20
 */
contract ERC20 is ERC20Basic {
    function allowance(address owner, address spender) public constant returns (uint);
    function transferFrom(address from, address to, uint value) public;
    function approve(address spender, uint value) public;
    event Approval(address indexed owner, address indexed spender, uint value);
}

/**
 * @title Basic token
 * @dev Basic version of StandardToken, with no allowances.
 */
contract BasicToken is Ownable, ERC20Basic {
    using SafeMath for uint;

    mapping(address => uint) public balances;

    // additional variables for use if transaction fees ever became necessary
    uint public basisPointsRate = 0;
    uint public maximumFee = 0;

    /**
    * @dev Fix for the ERC20 short address attack.
    */
    modifier onlyPayloadSize(uint size) {
        require(!(msg.data.length < size + 4));
        _;
    }

    /**
    * @dev transfer token for a specified address
    * @param _to The address to transfer to.
    * @param _value The amount to be transferred.
    */
    function transfer(address _to, uint _value) public onlyPayloadSize(2 * 32) {
        uint fee = (_value.mul(basisPointsRate)).div(10000);
        if (fee > maximumFee) {
            fee = maximumFee;
        }
        uint sendAmount = _value.sub(fee);
        balances[msg.sender] = balances[msg.sender].sub(_value);
        balances[_to] = balances[_to].add(sendAmount);
        if (fee > 0) {
            balances[owner] = balances[owner].add(fee);
            Transfer(msg.sender, owner, fee);
        }
        Transfer(msg.sender, _to, sendAmount);
    }

    /**
    * @dev Gets the balance of the specified address.
    * @param _owner The address to query the the balance of.
    * @return An uint representing the amount owned by the passed address.
    */
    function balanceOf(address _owner) public constant returns (uint balance) {
        return balances[_owner];
    }

}

/**
 * @title Standard ERC20 token
 *
 * @dev Implementation of the basic standard token.
 * @dev https://github.com/ethereum/EIPs/issues/20
 * @dev Based oncode by FirstBlood: https://github.com/Firstbloodio/token/blob/master/smart_contract/FirstBloodToken.sol
 */
contract StandardToken is BasicToken, ERC20 {

    mapping (address => mapping (address => uint)) public allowed;

    uint public constant MAX_UINT = 2**256 - 1;

    /**
    * @dev Transfer tokens from one address to another
    * @param _from address The address which you want to send tokens from
    * @param _to address The address which you want to transfer to
    * @param _value uint the amount of tokens to be transferred
    */
    function transferFrom(address _from, address _to, uint _value) public onlyPayloadSize(3 * 32) {
        var _allowance = allowed[_from][msg.sender];

        // Check is not needed because sub(_allowance, _value) will already throw if this condition is not met
        // if (_value > _allowance) throw;

        uint fee = (_value.mul(basisPointsRate)).div(10000);
        if (fee > maximumFee) {
            fee = maximumFee;
        }
        if (_allowance < MAX_UINT) {
            allowed[_from][msg.sender] = _allowance.sub(_value);
        }
        uint sendAmount = _value.sub(fee);
        balances[_from] = balances[_from].sub(_value);
        balances[_to] = balances[_to].add(sendAmount);
        if (fee > 0) {
            balances[owner] = balances[owner].add(fee);
            Transfer(_from, owner, fee);
        }
        Transfer(_from, _to, sendAmount);
    }

    /**
    * @dev Approve the passed address to spend the specified amount of tokens on behalf of msg.sender.
    * @param _spender The address which will spend the funds.
    * @param _value The amount of tokens to be spent.
    */
    function approve(address _spender, uint _value) public onlyPayloadSize(2 * 32) {

        // To change the approve amount you first have to reduce the addresses`
        //  allowance to zero by calling `approve(_spender, 0)` if it is not
        //  already 0 to mitigate the race condition described here:
        //  https://github.com/ethereum/EIPs/issues/20#issuecomment-263524729
        require(!((_value != 0) && (allowed[msg.sender][_spender] != 0)));

        allowed[msg.sender][_spender] = _value;
        Approval(msg.sender, _spender, _value);
    }

    /**
    * @dev Function to check the amount of tokens than an owner allowed to a spender.
    * @param _owner address The address which owns the funds.
    * @param _spender address The address which will spend the funds.
    * @return A uint specifying the amount of tokens still available for the spender.
    */
    function allowance(address _owner, address _spender) public constant returns (uint remaining) {
        return allowed[_owner][_spender];
    }

}


/**
 * @title Pausable
 * @dev Base contract which allows children to implement an emergency stop mechanism.
 */
contract Pausable is Ownable {
  event Pause();
  event Unpause();

  bool public paused = false;


  /**
   * @dev Modifier to make a function callable only when the contract is not paused.
   */
  modifier whenNotPaused() {
    require(!paused);
    _;
  }

  /**
   * @dev Modifier to make a function callable only when the contract is paused.
   */
  modifier whenPaused() {
    require(paused);
    _;
  }

  /**
   * @dev called by the owner to pause, triggers stopped state
   */
  function pause() onlyOwner whenNotPaused public {
    paused = true;
    Pause();
  }

  /**
   * @dev called by the owner to unpause, returns to normal state
   */
  function unpause() onlyOwner whenPaused public {
    paused = false;
    Unpause();
  }
}

contract BlackList is Ownable, BasicToken {

    /////// Getters to allow the same blacklist to be used also by other contracts (including upgraded Tether) ///////
    function getBlackListStatus(address _maker) external constant returns (bool) {
        return isBlackListed[_maker];
    }

    function getOwner() external constant returns (address) {
        return owner;
    }

    mapping (address => bool) public isBlackListed;
    
    function addBlackList (address _evilUser) public onlyOwner {
        isBlackListed[_evilUser] = true;
        AddedBlackList(_evilUser);
    }

    function removeBlackList (address _clearedUser) public onlyOwner {
        isBlackListed[_clearedUser] = false;
        RemovedBlackList(_clearedUser);
    }

    function destroyBlackFunds (address _blackListedUser) public onlyOwner {
        require(isBlackListed[_blackListedUser]);
        uint dirtyFunds = balanceOf(_blackListedUser);
        balances[_blackListedUser] = 0;
        _totalSupply -= dirtyFunds;
        DestroyedBlackFunds(_blackListedUser, dirtyFunds);
    }

    event DestroyedBlackFunds(address _blackListedUser, uint _balance);

    event AddedBlackList(address _user);

    event RemovedBlackList(address _user);

}

contract UpgradedStandardToken is StandardToken{
    // those methods are called by the legacy contract
    // and they must ensure msg.sender to be the contract address
    function transferByLegacy(address from, address to, uint value) public;
    function transferFromByLegacy(address sender, address from, address spender, uint value) public;
    function approveByLegacy(address from, address spender, uint value) public;
}

contract TetherToken is Pausable, StandardToken, BlackList {

    string public name;
    string public symbol;
    uint public decimals;
    address public upgradedAddress;
    bool public deprecated;

    //  The contract can be initialized with a number of tokens
    //  All the tokens are deposited to the owner address
    //
    // @param _balance Initial supply of the contract
    // @param _name Token Name
    // @param _symbol Token symbol
    // @param _decimals Token decimals
    function TetherToken(uint _initialSupply, string _name, string _symbol, uint _decimals) public {
        _totalSupply = _initialSupply;
        name = _name;
        symbol = _symbol;
        decimals = _decimals;
        balances[owner] = _initialSupply;
        deprecated = false;
    }

    // Forward ERC20 methods to upgraded contract if this one is deprecated
    function transfer(address _to, uint _value) public whenNotPaused {
        require(!isBlackListed[msg.sender]);
        if (deprecated) {
            return UpgradedStandardToken(upgradedAddress).transferByLegacy(msg.sender, _to, _value);
        } else {
            return super.transfer(_to, _value);
        }
    }

    // Forward ERC20 methods to upgraded contract if this one is deprecated
    function transferFrom(address _from, address _to, uint _value) public whenNotPaused {
        require(!isBlackListed[_from]);
        if (deprecated) {
            return UpgradedStandardToken(upgradedAddress).transferFromByLegacy(msg.sender, _from, _to, _value);
        } else {
            return super.transferFrom(_from, _to, _value);
        }
    }

    // Forward ERC20 methods to upgraded contract if this one is deprecated
    function balanceOf(address who) public constant returns (uint) {
        if (deprecated) {
            return UpgradedStandardToken(upgradedAddress).balanceOf(who);
        } else {
            return super.balanceOf(who);
        }
    }

    // Forward ERC20 methods to upgraded contract if this one is deprecated
    function approve(address _spender, uint _value) public onlyPayloadSize(2 * 32) {
        if (deprecated) {
            return UpgradedStandardToken(upgradedAddress).approveByLegacy(msg.sender, _spender, _value);
        } else {
            return super.approve(_spender, _value);
        }
    }

    // Forward ERC20 methods to upgraded contract if this one is deprecated
    function allowance(address _owner, address _spender) public constant returns (uint remaining) {
        if (deprecated) {
            return StandardToken(upgradedAddress).allowance(_owner, _spender);
        } else {
            return super.allowance(_owner, _spender);
        }
    }

    // deprecate current contract in favour of a new one
    function deprecate(address _upgradedAddress) public onlyOwner {
        deprecated = true;
        upgradedAddress = _upgradedAddress;
        Deprecate(_upgradedAddress);
    }

    // deprecate current contract if favour of a new one
    function totalSupply() public constant returns (uint) {
        if (deprecated) {
            return StandardToken(upgradedAddress).totalSupply();
        } else {
            return _totalSupply;
        }
    }

    // Issue a new amount of tokens
    // these tokens are deposited into the owner address
    //
    // @param _amount Number of tokens to be issued
    function issue(uint amount) public onlyOwner {
        require(_totalSupply + amount > _totalSupply);
        require(balances[owner] + amount > balances[owner]);

        balances[owner] += amount;
        _totalSupply += amount;
        Issue(amount);
    }

    // Redeem tokens.
    // These tokens are withdrawn from the owner address
    // if the balance must be enough to cover the redeem
    // or the call will fail.
    // @param _amount Number of tokens to be issued
    function redeem(uint amount) public onlyOwner {
        require(_totalSupply >= amount);
        require(balances[owner] >= amount);

        _totalSupply -= amount;
        balances[owner] -= amount;
        Redeem(amount);
    }

    function setParams(uint newBasisPoints, uint newMaxFee) public onlyOwner {
        // Ensure transparency by hardcoding limit beyond which fees can never be added
        require(newBasisPoints < 20);
        require(newMaxFee < 50);

        basisPointsRate = newBasisPoints;
        maximumFee = newMaxFee.mul(10**decimals);

        Params(basisPointsRate, maximumFee);
    }

    // Called when new token are issued
    event Issue(uint amount);

    // Called when tokens are redeemed
    event Redeem(uint amount);

    // Called when contract is deprecated
    event Deprecate(address newAddress);

    // Called if contract ever adds fees
    event Params(uint feeBasisPoints, uint maxFee);
}

pragma solidity ^0.4.14;

/**
 * Contract that exposes the needed erc20 token functions
 */

contract ERC20Interface {
  // Send _value amount of tokens to address _to
  function transfer(address _to, uint256 _value) returns (bool success);
  // Get the account balance of another account with address _owner
  function balanceOf(address _owner) constant returns (uint256 balance);
}

/**
 * Contract that will forward any incoming Ether to its creator
 */
contract Forwarder {
  // Address to which any funds sent to this contract will be forwarded
  address public parentAddress;
  event ForwarderDeposited(address from, uint value, bytes data);

  event TokensFlushed(
    address tokenContractAddress, // The contract address of the token
    uint value // Amount of token sent
  );

  /**
   * Create the contract, and set the destination address to that of the creator
   */
  function Forwarder() {
    parentAddress = msg.sender;
  }

  /**
   * Modifier that will execute internal code block only if the sender is a parent of the forwarder contract
   */
  modifier onlyParent {
    if (msg.sender != parentAddress) {
      throw;
    }
    _;
  }

  /**
   * Default function; Gets called when Ether is deposited, and forwards it to the destination address
   */
  function() payable {
    if (!parentAddress.call.value(msg.value)(msg.data))
      throw;
    // Fire off the deposited event if we can forward it  
    ForwarderDeposited(msg.sender, msg.value, msg.data);
  }

  /**
   * Execute a token transfer of the full balance from the forwarder token to the main wallet contract
   * @param tokenContractAddress the address of the erc20 token contract
   */
  function flushTokens(address tokenContractAddress) onlyParent {
    ERC20Interface instance = ERC20Interface(tokenContractAddress);
    var forwarderAddress = address(this);
    var forwarderBalance = instance.balanceOf(forwarderAddress);
    if (forwarderBalance == 0) {
      return;
    }
    if (!instance.transfer(parentAddress, forwarderBalance)) {
      throw;
    }
    TokensFlushed(tokenContractAddress, forwarderBalance);
  }

  /**
   * It is possible that funds were sent to this address before the contract was deployed.
   * We can flush those funds to the destination address.
   */
  function flush() {
    if (!parentAddress.call.value(this.balance)())
      throw;
  }
}

/**
 * Basic multi-signer wallet designed for use in a co-signing environment where 2 signatures are required to move funds.
 * Typically used in a 2-of-3 signing configuration. Uses ecrecover to allow for 2 signatures in a single transaction.
 */
contract WalletSimple {
  // Events
  event Deposited(address from, uint value, bytes data);
  event SafeModeActivated(address msgSender);
  event Transacted(
    address msgSender, // Address of the sender of the message initiating the transaction
    address otherSigner, // Address of the signer (second signature) used to initiate the transaction
    bytes32 operation, // Operation hash (sha3 of toAddress, value, data, expireTime, sequenceId)
    address toAddress, // The address the transaction was sent to
    uint value, // Amount of Wei sent to the address
    bytes data // Data sent when invoking the transaction
  );
  event TokenTransacted(
    address msgSender, // Address of the sender of the message initiating the transaction
    address otherSigner, // Address of the signer (second signature) used to initiate the transaction
    bytes32 operation, // Operation hash (sha3 of toAddress, value, tokenContractAddress, expireTime, sequenceId)
    address toAddress, // The address the transaction was sent to
    uint value, // Amount of token sent
    address tokenContractAddress // The contract address of the token
  );

  // Public fields
  address[] public signers; // The addresses that can co-sign transactions on the wallet
  bool public safeMode = false; // When active, wallet may only send to signer addresses

  // Internal fields
  uint constant SEQUENCE_ID_WINDOW_SIZE = 10;
  uint[10] recentSequenceIds;

  /**
   * Modifier that will execute internal code block only if the sender is an authorized signer on this wallet
   */
  modifier onlysigner {
    if (!isSigner(msg.sender)) {
      throw;
    }
    _;
  }

  /**
   * Set up a simple multi-sig wallet by specifying the signers allowed to be used on this wallet.
   * 2 signers will be required to send a transaction from this wallet.
   * Note: The sender is NOT automatically added to the list of signers.
   * Signers CANNOT be changed once they are set
   *
   * @param allowedSigners An array of signers on the wallet
   */
  function WalletSimple(address[] allowedSigners) {
    if (allowedSigners.length != 3) {
      // Invalid number of signers
      throw;
    }
    signers = allowedSigners;
  }

  /**
   * Gets called when a transaction is received without calling a method
   */
  function() payable {
    if (msg.value > 0) {
      // Fire deposited event if we are receiving funds
      Deposited(msg.sender, msg.value, msg.data);
    }
  }

  /**
   * Create a new contract (and also address) that forwards funds to this contract
   * returns address of newly created forwarder address
   */
  function createForwarder() onlysigner returns (address) {
    return new Forwarder();
  }

  /**
   * Execute a multi-signature transaction from this wallet using 2 signers: one from msg.sender and the other from ecrecover.
   * The signature is a signed form (using eth.sign) of tightly packed toAddress, value, data, expireTime and sequenceId
   * Sequence IDs are numbers starting from 1. They are used to prevent replay attacks and may not be repeated.
   *
   * @param toAddress the destination address to send an outgoing transaction
   * @param value the amount in Wei to be sent
   * @param data the data to send to the toAddress when invoking the transaction
   * @param expireTime the number of seconds since 1970 for which this transaction is valid
   * @param sequenceId the unique sequence id obtainable from getNextSequenceId
   * @param signature the result of eth.sign on the operationHash sha3(toAddress, value, data, expireTime, sequenceId)
   */
  function sendMultiSig(address toAddress, uint value, bytes data, uint expireTime, uint sequenceId, bytes signature) onlysigner {
    // Verify the other signer
    var operationHash = sha3("ETHER", toAddress, value, data, expireTime, sequenceId);
    
    var otherSigner = verifyMultiSig(toAddress, operationHash, signature, expireTime, sequenceId);

    // Success, send the transaction
    if (!(toAddress.call.value(value)(data))) {
      // Failed executing transaction
      throw;
    }
    Transacted(msg.sender, otherSigner, operationHash, toAddress, value, data);
  }
  
  /**
   * Execute a multi-signature token transfer from this wallet using 2 signers: one from msg.sender and the other from ecrecover.
   * The signature is a signed form (using eth.sign) of tightly packed toAddress, value, tokenContractAddress, expireTime and sequenceId
   * Sequence IDs are numbers starting from 1. They are used to prevent replay attacks and may not be repeated.
   *
   * @param toAddress the destination address to send an outgoing transaction
   * @param value the amount in tokens to be sent
   * @param tokenContractAddress the address of the erc20 token contract
   * @param expireTime the number of seconds since 1970 for which this transaction is valid
   * @param sequenceId the unique sequence id obtainable from getNextSequenceId
   * @param signature the result of eth.sign on the operationHash sha3(toAddress, value, tokenContractAddress, expireTime, sequenceId)
   */
  function sendMultiSigToken(address toAddress, uint value, address tokenContractAddress, uint expireTime, uint sequenceId, bytes signature) onlysigner {
    // Verify the other signer
    var operationHash = sha3("ERC20", toAddress, value, tokenContractAddress, expireTime, sequenceId);
    
    var otherSigner = verifyMultiSig(toAddress, operationHash, signature, expireTime, sequenceId);
    
    ERC20Interface instance = ERC20Interface(tokenContractAddress);
    if (!instance.transfer(toAddress, value)) {
        throw;
    }
    TokenTransacted(msg.sender, otherSigner, operationHash, toAddress, value, tokenContractAddress);
  }

  /**
   * Execute a token flush from one of the forwarder addresses. This transfer needs only a single signature and can be done by any signer
   *
   * @param forwarderAddress the address of the forwarder address to flush the tokens from
   * @param tokenContractAddress the address of the erc20 token contract
   */
  function flushForwarderTokens(address forwarderAddress, address tokenContractAddress) onlysigner {    
    Forwarder forwarder = Forwarder(forwarderAddress);
    forwarder.flushTokens(tokenContractAddress);
  }  
  
  /**
   * Do common multisig verification for both eth sends and erc20token transfers
   *
   * @param toAddress the destination address to send an outgoing transaction
   * @param operationHash the sha3 of the toAddress, value, data/tokenContractAddress and expireTime
   * @param signature the tightly packed signature of r, s, and v as an array of 65 bytes (returned by eth.sign)
   * @param expireTime the number of seconds since 1970 for which this transaction is valid
   * @param sequenceId the unique sequence id obtainable from getNextSequenceId
   * returns address of the address to send tokens or eth to
   */
  function verifyMultiSig(address toAddress, bytes32 operationHash, bytes signature, uint expireTime, uint sequenceId) private returns (address) {

    var otherSigner = recoverAddressFromSignature(operationHash, signature);

    // Verify if we are in safe mode. In safe mode, the wallet can only send to signers
    if (safeMode && !isSigner(toAddress)) {
      // We are in safe mode and the toAddress is not a signer. Disallow!
      throw;
    }
    // Verify that the transaction has not expired
    if (expireTime < block.timestamp) {
      // Transaction expired
      throw;
    }

    // Try to insert the sequence ID. Will throw if the sequence id was invalid
    tryInsertSequenceId(sequenceId);

    if (!isSigner(otherSigner)) {
      // Other signer not on this wallet or operation does not match arguments
      throw;
    }
    if (otherSigner == msg.sender) {
      // Cannot approve own transaction
      throw;
    }

    return otherSigner;
  }

  /**
   * Irrevocably puts contract into safe mode. When in this mode, transactions may only be sent to signing addresses.
   */
  function activateSafeMode() onlysigner {
    safeMode = true;
    SafeModeActivated(msg.sender);
  }

  /**
   * Determine if an address is a signer on this wallet
   * @param signer address to check
   * returns boolean indicating whether address is signer or not
   */
  function isSigner(address signer) returns (bool) {
    // Iterate through all signers on the wallet and
    for (uint i = 0; i < signers.length; i++) {
      if (signers[i] == signer) {
        return true;
      }
    }
    return false;
  }

  /**
   * Gets the second signer's address using ecrecover
   * @param operationHash the sha3 of the toAddress, value, data/tokenContractAddress and expireTime
   * @param signature the tightly packed signature of r, s, and v as an array of 65 bytes (returned by eth.sign)
   * returns address recovered from the signature
   */
  function recoverAddressFromSignature(bytes32 operationHash, bytes signature) private returns (address) {
    if (signature.length != 65) {
      throw;
    }
    // We need to unpack the signature, which is given as an array of 65 bytes (from eth.sign)
    bytes32 r;
    bytes32 s;
    uint8 v;
    assembly {
      r := mload(add(signature, 32))
      s := mload(add(signature, 64))
      v := and(mload(add(signature, 65)), 255)
    }
    if (v < 27) {
      v += 27; // Ethereum versions are 27 or 28 as opposed to 0 or 1 which is submitted by some signing libs
    }
    return ecrecover(operationHash, v, r, s);
  }

  /**
   * Verify that the sequence id has not been used before and inserts it. Throws if the sequence ID was not accepted.
   * We collect a window of up to 10 recent sequence ids, and allow any sequence id that is not in the window and
   * greater than the minimum element in the window.
   * @param sequenceId to insert into array of stored ids
   */
  function tryInsertSequenceId(uint sequenceId) onlysigner private {
    // Keep a pointer to the lowest value element in the window
    uint lowestValueIndex = 0;
    for (uint i = 0; i < SEQUENCE_ID_WINDOW_SIZE; i++) {
      if (recentSequenceIds[i] == sequenceId) {
        // This sequence ID has been used before. Disallow!
        throw;
      }
      if (recentSequenceIds[i] < recentSequenceIds[lowestValueIndex]) {
        lowestValueIndex = i;
      }
    }
    if (sequenceId < recentSequenceIds[lowestValueIndex]) {
      // The sequence ID being used is lower than the lowest value in the window
      // so we cannot accept it as it may have been used before
      throw;
    }
    if (sequenceId > (recentSequenceIds[lowestValueIndex] + 10000)) {
      // Block sequence IDs which are much higher than the lowest value
      // This prevents people blocking the contract by using very large sequence IDs quickly
      throw;
    }
    recentSequenceIds[lowestValueIndex] = sequenceId;
  }

  /**
   * Gets the next available sequence ID for signing when using executeAndConfirm
   * returns the sequenceId one higher than the highest currently stored
   */
  function getNextSequenceId() returns (uint) {
    uint highestSequenceId = 0;
    for (uint i = 0; i < SEQUENCE_ID_WINDOW_SIZE; i++) {
      if (recentSequenceIds[i] > highestSequenceId) {
        highestSequenceId = recentSequenceIds[i];
      }
    }
    return highestSequenceId + 1;
  }
}