Forkchoice Ethereum Mainnet

pragma solidity ^0.5.10;

/** @title  A contract for generating unique identifiers
  *
  * @notice  A contract that provides an identifier generation scheme,
  * guaranteeing uniqueness across all contracts that inherit from it,
  * as well as the unpredictability of future identifiers.
  *
  * @dev  This contract is intended to be inherited by any contract that
  * implements the callback software pattern for cooperative custodianship.
  *
*/
contract LockRequestable {

    // MEMBERS
    /// @notice  the count of all invocations of `generateLockId`.
    uint256 public lockRequestCount;

    // CONSTRUCTOR
    constructor() public {
        lockRequestCount = 0;
    }

    // FUNCTIONS
    /** @notice  Returns a fresh unique identifier.
      *
      * @dev the generation scheme uses three components.
      * First, the blockhash of the previous block.
      * Second, the deployed address.
      * Third, the next value of the counter.
      * This ensures that identifiers are unique across all contracts
      * following this scheme, and that future identifiers are
      * unpredictable.
      *
      * @return a 32-byte unique identifier.
    */
    function generateLockId() internal returns (bytes32 lockId) {
        return keccak256(abi.encodePacked(blockhash(block.number - 1), address(this), ++lockRequestCount));
    }
}

contract ERC20Interface {

    // METHODS

    // NOTE:
    //   public getter functions are not currently recognised as an
    //   implementation of the matching abstract function by the compiler.

    // https://github.com/ethereum/EIPs/blob/master/EIPS/eip-20.md#name
    // function name() public view returns (string);

    // https://github.com/ethereum/EIPs/blob/master/EIPS/eip-20.md#symbol
    // function symbol() public view returns (string);

    // https://github.com/ethereum/EIPs/blob/master/EIPS/eip-20.md#totalsupply
    // function decimals() public view returns (uint8);

    // https://github.com/ethereum/EIPs/blob/master/EIPS/eip-20.md#totalsupply
    function totalSupply() public view returns (uint256);

    // https://github.com/ethereum/EIPs/blob/master/EIPS/eip-20.md#balanceof
    function balanceOf(address _owner) public view returns (uint256 balance);

    // https://github.com/ethereum/EIPs/blob/master/EIPS/eip-20.md#transfer
    function transfer(address _to, uint256 _value) public returns (bool success);

    // https://github.com/ethereum/EIPs/blob/master/EIPS/eip-20.md#transferfrom
    function transferFrom(address _from, address _to, uint256 _value) public returns (bool success);

    // https://github.com/ethereum/EIPs/blob/master/EIPS/eip-20.md#approve
    function approve(address _spender, uint256 _value) public returns (bool success);

    // https://github.com/ethereum/EIPs/blob/master/EIPS/eip-20.md#allowance
    function allowance(address _owner, address _spender) public view returns (uint256 remaining);

    // EVENTS
    // https://github.com/ethereum/EIPs/blob/master/EIPS/eip-20.md#transfer-1
    event Transfer(address indexed _from, address indexed _to, uint256 _value);

    // https://github.com/ethereum/EIPs/blob/master/EIPS/eip-20.md#approval
    event Approval(address indexed _owner, address indexed _spender, uint256 _value);
}

/** @title  A dual control contract.
  *
  * @notice  A general-purpose contract that implements dual control over
  * co-operating contracts through a callback mechanism.
  *
  * @dev  This contract implements dual control through a 2-of-N
  * threshold multi-signature scheme. The contract recognizes a set of N signers,
  * and will unlock requests with signatures from any distinct pair of them.
  * This contract signals the unlocking through a co-operative callback
  * scheme.
  * This contract also provides time lock and revocation features.
  * Requests made by a 'primary' account have a default time lock applied.
  * All other requests must pay a 1 ETH stake and have an extended time lock
  * applied.
  * A request that is completed will prevent all previous pending requests
  * that share the same callback from being completed: this is the
  * revocation feature.
  *
  */
contract Custodian {

    // TYPES
    /** @dev  The `Request` struct stores a pending unlocking.
      * `callbackAddress` and `callbackSelector` are the data required to
      * make a callback. The custodian completes the process by
      * calling `callbackAddress.call(callbackSelector, lockId)`, which
      * signals to the contract co-operating with the Custodian that
      * the 2-of-N signatures have been provided and verified.
      */
    struct Request {
        bytes32 lockId;
        bytes4 callbackSelector;  // bytes4 and address can be packed into 1 word
        address callbackAddress;
        uint256 idx;
        uint256 timestamp;
        bool extended;
    }

    // EVENTS
    /// @dev  Emitted by successful `requestUnlock` calls.
    event Requested(
        bytes32 _lockId,
        address _callbackAddress,
        bytes4 _callbackSelector,
        uint256 _nonce,
        address _whitelistedAddress,
        bytes32 _requestMsgHash,
        uint256 _timeLockExpiry
    );

    /// @dev  Emitted by `completeUnlock` calls on requests in the time-locked state.
    event TimeLocked(
        uint256 _timeLockExpiry,
        bytes32 _requestMsgHash
    );

    /// @dev  Emitted by successful `completeUnlock` calls.
    event Completed(
        bytes32 _lockId,
        bytes32 _requestMsgHash,
        address _signer1,
        address _signer2
    );

    /// @dev  Emitted by `completeUnlock` calls where the callback failed.
    event Failed(
        bytes32 _lockId,
        bytes32 _requestMsgHash,
        address _signer1,
        address _signer2
    );

    /// @dev  Emitted by successful `extendRequestTimeLock` calls.
    event TimeLockExtended(
        uint256 _timeLockExpiry,
        bytes32 _requestMsgHash
    );

     // MEMBERS
    /** @dev  The count of all requests.
      * This value is used as a nonce, incorporated into the request hash.
      */
    uint256 public requestCount;

    /// @dev  The set of signers: signatures from two signers unlock a pending request.
    mapping (address => bool) public signerSet;

    /// @dev  The map of request hashes to pending requests.
    mapping (bytes32 => Request) public requestMap;

    /// @dev  The map of callback addresses to callback selectors to request indexes.
    mapping (address => mapping (bytes4 => uint256)) public lastCompletedIdxs;

    /** @dev  The default period (in seconds) to time-lock requests.
      * All requests will be subject to this default time lock, and the duration
      * is fixed at contract creation.
      */
    uint256 public defaultTimeLock;

    /** @dev  The extended period (in seconds) to time-lock requests.
      * Requests not from the primary account are subject to this time lock.
      * The primary account may also elect to extend the time lock on requests
      * that originally received the default.
      */
    uint256 public extendedTimeLock;

    /// @dev  The primary account is the privileged account for making requests.
    address public primary;

    // CONSTRUCTOR
    constructor(
        address[] memory _signers,
        uint256 _defaultTimeLock,
        uint256 _extendedTimeLock,
        address _primary
    )
        public
    {
        // check for at least two `_signers`
        require(_signers.length >= 2, "at least two `_signers`");

         // validate time lock params
        require(_defaultTimeLock <= _extendedTimeLock, "valid timelock params");
        defaultTimeLock = _defaultTimeLock;
        extendedTimeLock = _extendedTimeLock;

        primary = _primary;

        // explicitly initialize `requestCount` to zero
        requestCount = 0;
        // turn the array into a set
        for (uint i = 0; i < _signers.length; i++) {
            // no zero addresses or duplicates
            require(_signers[i] != address(0) && !signerSet[_signers[i]], "no zero addresses or duplicates");
            signerSet[_signers[i]] = true;
        }
    }

    // MODIFIERS
    modifier onlyPrimary {
        require(msg.sender == primary, "only primary");
        _;
    }

     modifier onlySigner {
        require(signerSet[msg.sender], "only signer");
        _;
    }

    // METHODS
    /** @notice  Requests an unlocking with a lock identifier and a callback.
      *
      * @dev  If called by an account other than the primary a 1 ETH stake
      * must be paid. When the request is unlocked stake will be transferred to the message sender.
      * This is an anti-spam measure. As well as the callback
      * and the lock identifier parameters a 'whitelisted address' is required
      * for compatibility with existing signature schemes.
      *
      * @param  _lockId  The identifier of a pending request in a co-operating contract.
      * @param  _callbackAddress  The address of a co-operating contract.
      * @param  _callbackSelector  The function selector of a function within
      * the co-operating contract at address `_callbackAddress`.
      * @param  _whitelistedAddress  An address whitelisted in existing
      * offline control protocols.
      *
      * @return  requestMsgHash  The hash of a request message to be signed.
    */
    function requestUnlock(
        bytes32 _lockId,
        address _callbackAddress,
        bytes4 _callbackSelector,
        address _whitelistedAddress
    )
        public
        payable
        returns (bytes32 requestMsgHash)
    {
        require(msg.sender == primary || msg.value >= 1 ether, "sender is primary or stake is paid");

        // disallow using a zero value for the callback address
        require(_callbackAddress != address(0), "no zero value for callback address");

        uint256 requestIdx = ++requestCount;
        // compute a nonce value
        // - the blockhash prevents prediction of future nonces
        // - the address of this contract prevents conflicts with co-operating contracts using this scheme
        // - the counter prevents conflicts arising from multiple txs within the same block
        uint256 nonce = uint256(keccak256(abi.encodePacked(blockhash(block.number - 1), address(this), requestIdx)));

        requestMsgHash = keccak256(
            abi.encodePacked(
                nonce,
                _whitelistedAddress,
                uint256(0xFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF)
            )
        );
        requestMap[requestMsgHash] = Request({
            lockId: _lockId,
            callbackSelector: _callbackSelector,
            callbackAddress: _callbackAddress,
            idx: requestIdx,
            timestamp: block.timestamp,
            extended: false
        });

        // compute the expiry time
        uint256 timeLockExpiry = block.timestamp;
        if (msg.sender == primary) {
            timeLockExpiry += defaultTimeLock;
        } else {
            timeLockExpiry += extendedTimeLock;

            // any sender that is not the creator will get the extended time lock
            requestMap[requestMsgHash].extended = true;
        }

        emit Requested(_lockId, _callbackAddress, _callbackSelector, nonce, _whitelistedAddress, requestMsgHash, timeLockExpiry);
    }

    /** @notice  Completes a pending unlocking with two signatures.
      *
      * @dev  Given a request message hash as two signatures of it from
      * two distinct signers in the signer set, this function completes the
      * unlocking of the pending request by executing the callback.
      *
      * @param  _requestMsgHash  The request message hash of a pending request.
      * @param  _recoveryByte1  The public key recovery byte (27 or 28)
      * @param  _ecdsaR1  The R component of an ECDSA signature (R, S) pair
      * @param  _ecdsaS1  The S component of an ECDSA signature (R, S) pair
      * @param  _recoveryByte2  The public key recovery byte (27 or 28)
      * @param  _ecdsaR2  The R component of an ECDSA signature (R, S) pair
      * @param  _ecdsaS2  The S component of an ECDSA signature (R, S) pair
      *
      * @return  success  True if the callback successfully executed.
    */
    function completeUnlock(
        bytes32 _requestMsgHash,
        uint8 _recoveryByte1, bytes32 _ecdsaR1, bytes32 _ecdsaS1,
        uint8 _recoveryByte2, bytes32 _ecdsaR2, bytes32 _ecdsaS2
    )
        public
        onlySigner
        returns (bool success)
    {
        Request storage request = requestMap[_requestMsgHash];

        // copy storage to locals before `delete`
        bytes32 lockId = request.lockId;
        address callbackAddress = request.callbackAddress;
        bytes4 callbackSelector = request.callbackSelector;

        // failing case of the lookup if the callback address is zero
        require(callbackAddress != address(0), "no zero value for callback address");

        // reject confirms of earlier withdrawals buried under later confirmed withdrawals
        require(request.idx > lastCompletedIdxs[callbackAddress][callbackSelector],
        "reject confirms of earlier withdrawals buried under later confirmed withdrawals");

        address signer1 = ecrecover(
            keccak256(abi.encodePacked("\x19Ethereum Signed Message:\n32", _requestMsgHash)),
            _recoveryByte1,
            _ecdsaR1,
            _ecdsaS1
        );
        require(signerSet[signer1], "signer is set");

        address signer2 = ecrecover(
            keccak256(abi.encodePacked("\x19Ethereum Signed Message:\n32", _requestMsgHash)),
            _recoveryByte2,
            _ecdsaR2,
            _ecdsaS2
        );
        require(signerSet[signer2], "signer is set");
        require(signer1 != signer2, "signers are different");

        if (request.extended && ((block.timestamp - request.timestamp) < extendedTimeLock)) {
            emit TimeLocked(request.timestamp + extendedTimeLock, _requestMsgHash);
            return false;
        } else if ((block.timestamp - request.timestamp) < defaultTimeLock) {
            emit TimeLocked(request.timestamp + defaultTimeLock, _requestMsgHash);
            return false;
        } else {
            if (address(this).balance > 0) {
                // reward sender with anti-spam payments
                msg.sender.transfer(address(this).balance);
            }

            // raise the waterline for the last completed unlocking
            lastCompletedIdxs[callbackAddress][callbackSelector] = request.idx;
            // and delete the request
            delete requestMap[_requestMsgHash];

            // invoke callback
            (success,) = callbackAddress.call(abi.encodeWithSelector(callbackSelector, lockId));

            if (success) {
                emit Completed(lockId, _requestMsgHash, signer1, signer2);
            } else {
                emit Failed(lockId, _requestMsgHash, signer1, signer2);
            }
        }
    }

    /** @notice  Reclaim the storage of a pending request that is uncompletable.
      *
      * @dev  If a pending request shares the callback (address and selector) of
      * a later request has been completed, then the request can no longer
      * be completed. This function will reclaim the contract storage of the
      * pending request.
      *
      * @param  _requestMsgHash  The request message hash of a pending request.
    */
    function deleteUncompletableRequest(bytes32 _requestMsgHash) public {
        Request storage request = requestMap[_requestMsgHash];

        uint256 idx = request.idx;

        require(0 < idx && idx < lastCompletedIdxs[request.callbackAddress][request.callbackSelector],
        "there must be a completed latter request with same callback");

        delete requestMap[_requestMsgHash];
    }

    /** @notice  Extend the time lock of a pending request.
      *
      * @dev  Requests made by the primary account receive the default time lock.
      * This function allows the primary account to apply the extended time lock
      * to one its own requests.
      *
      * @param  _requestMsgHash  The request message hash of a pending request.
    */
    function extendRequestTimeLock(bytes32 _requestMsgHash) public onlyPrimary {
        Request storage request = requestMap[_requestMsgHash];

        // reject ‘null’ results from the map lookup
        // this can only be the case if an unknown `_requestMsgHash` is received
        require(request.callbackAddress != address(0), "reject ‘null’ results from the map lookup");

        // `extendRequestTimeLock` must be idempotent
        require(request.extended != true, "`extendRequestTimeLock` must be idempotent");

        // set the `extended` flag; note that this is never unset
        request.extended = true;

        emit TimeLockExtended(request.timestamp + extendedTimeLock, _requestMsgHash);
    }
}

/** @title  A contract to inherit upgradeable custodianship.
  *
  * @notice  A contract that provides re-usable code for upgradeable
  * custodianship. That custodian may be an account or another contract.
  *
  * @dev  This contract is intended to be inherited by any contract
  * requiring a custodian to control some aspect of its functionality.
  * This contract provides the mechanism for that custodianship to be
  * passed from one custodian to the next.
  *
*/
contract CustodianUpgradeable is LockRequestable {

    // TYPES
    /// @dev  The struct type for pending custodian changes.
    struct CustodianChangeRequest {
        address proposedNew;
    }

    // MEMBERS
    /// @dev  The address of the account or contract that acts as the custodian.
    address public custodian;

    /// @dev  The map of lock ids to pending custodian changes.
    mapping (bytes32 => CustodianChangeRequest) public custodianChangeReqs;

    // CONSTRUCTOR
    constructor(
        address _custodian
    )
      LockRequestable()
      public
    {
        custodian = _custodian;
    }

    // MODIFIERS
    modifier onlyCustodian {
        require(msg.sender == custodian, "only custodian");
        _;
    }

    // PUBLIC FUNCTIONS
    // (UPGRADE)

    /** @notice  Requests a change of the custodian associated with this contract.
      *
      * @dev  Returns a unique lock id associated with the request.
      * Anyone can call this function, but confirming the request is authorized
      * by the custodian.
      *
      * @param  _proposedCustodian  The address of the new custodian.
      * @return  lockId  A unique identifier for this request.
      */
    function requestCustodianChange(address _proposedCustodian) public returns (bytes32 lockId) {
        require(_proposedCustodian != address(0), "no null value for `_proposedCustodian`");

        lockId = generateLockId();

        custodianChangeReqs[lockId] = CustodianChangeRequest({
            proposedNew: _proposedCustodian
        });

        emit CustodianChangeRequested(lockId, msg.sender, _proposedCustodian);
    }

    /** @notice  Confirms a pending change of the custodian associated with this contract.
      *
      * @dev  When called by the current custodian with a lock id associated with a
      * pending custodian change, the `address custodian` member will be updated with the
      * requested address.
      *
      * @param  _lockId  The identifier of a pending change request.
      */
    function confirmCustodianChange(bytes32 _lockId) public onlyCustodian {
        custodian = getCustodianChangeReq(_lockId);

        delete custodianChangeReqs[_lockId];

        emit CustodianChangeConfirmed(_lockId, custodian);
    }

    // PRIVATE FUNCTIONS
    function getCustodianChangeReq(bytes32 _lockId) private view returns (address _proposedNew) {
        CustodianChangeRequest storage changeRequest = custodianChangeReqs[_lockId];

        // reject ‘null’ results from the map lookup
        // this can only be the case if an unknown `_lockId` is received
        require(changeRequest.proposedNew != address(0), "reject ‘null’ results from the map lookup");

        return changeRequest.proposedNew;
    }

    //EVENTS
    /// @dev  Emitted by successful `requestCustodianChange` calls.
    event CustodianChangeRequested(
        bytes32 _lockId,
        address _msgSender,
        address _proposedCustodian
    );

    /// @dev Emitted by successful `confirmCustodianChange` calls.
    event CustodianChangeConfirmed(bytes32 _lockId, address _newCustodian);
}

/** @title  A contract to inherit upgradeable token implementations.
  *
  * @notice  A contract that provides re-usable code for upgradeable
  * token implementations. It itself inherits from `CustodianUpgradable`
  * as the upgrade process is controlled by the custodian.
  *
  * @dev  This contract is intended to be inherited by any contract
  * requiring a reference to the active token implementation, either
  * to delegate calls to it, or authorize calls from it. This contract
  * provides the mechanism for that implementation to be replaced,
  * which constitutes an implementation upgrade.
  *
  */
contract ERC20ImplUpgradeable is CustodianUpgradeable  {

    // TYPES
    /// @dev  The struct type for pending implementation changes.
    struct ImplChangeRequest {
        address proposedNew;
    }

    // MEMBERS
    // @dev  The reference to the active token implementation.
    ERC20Impl public erc20Impl;

    /// @dev  The map of lock ids to pending implementation changes.
    mapping (bytes32 => ImplChangeRequest) public implChangeReqs;

    // CONSTRUCTOR
    constructor(address _custodian) CustodianUpgradeable(_custodian) public {
        erc20Impl = ERC20Impl(0x0);
    }

    // MODIFIERS
    modifier onlyImpl {
        require(msg.sender == address(erc20Impl), "only ERC20Impl");
        _;
    }

    // PUBLIC FUNCTIONS
    // (UPGRADE)
    /** @notice  Requests a change of the active implementation associated
      * with this contract.
      *
      * @dev  Returns a unique lock id associated with the request.
      * Anyone can call this function, but confirming the request is authorized
      * by the custodian.
      *
      * @param  _proposedImpl  The address of the new active implementation.
      * @return  lockId  A unique identifier for this request.
      */
    function requestImplChange(address _proposedImpl) public returns (bytes32 lockId) {
        require(_proposedImpl != address(0), "no null value for `_proposedImpl`");

        lockId = generateLockId();

        implChangeReqs[lockId] = ImplChangeRequest({
            proposedNew: _proposedImpl
        });

        emit ImplChangeRequested(lockId, msg.sender, _proposedImpl);
    }

    /** @notice  Confirms a pending change of the active implementation
      * associated with this contract.
      *
      * @dev  When called by the custodian with a lock id associated with a
      * pending change, the `ERC20Impl erc20Impl` member will be updated
      * with the requested address.
      *
      * @param  _lockId  The identifier of a pending change request.
      */
    function confirmImplChange(bytes32 _lockId) public onlyCustodian {
        erc20Impl = getImplChangeReq(_lockId);

        delete implChangeReqs[_lockId];

        emit ImplChangeConfirmed(_lockId, address(erc20Impl));
    }

    // PRIVATE FUNCTIONS
    function getImplChangeReq(bytes32 _lockId) private view returns (ERC20Impl _proposedNew) {
        ImplChangeRequest storage changeRequest = implChangeReqs[_lockId];

        // reject ‘null’ results from the map lookup
        // this can only be the case if an unknown `_lockId` is received
        require(changeRequest.proposedNew != address(0), "reject ‘null’ results from the map lookup");

        return ERC20Impl(changeRequest.proposedNew);
    }

    //EVENTS
    /// @dev  Emitted by successful `requestImplChange` calls.
    event ImplChangeRequested(
        bytes32 _lockId,
        address _msgSender,
        address _proposedImpl
    );

    /// @dev Emitted by successful `confirmImplChange` calls.
    event ImplChangeConfirmed(bytes32 _lockId, address _newImpl);
}

/** @title  Public interface to ERC20 compliant token.
  *
  * @notice  This contract is a permanent entry point to an ERC20 compliant
  * system of contracts.
  *
  * @dev  This contract contains no business logic and instead
  * delegates to an instance of ERC20Impl. This contract also has no storage
  * that constitutes the operational state of the token. This contract is
  * upgradeable in the sense that the `custodian` can update the
  * `erc20Impl` address, thus redirecting the delegation of business logic.
  * The `custodian` is also authorized to pass custodianship.
  *
*/
contract ERC20Proxy is ERC20Interface, ERC20ImplUpgradeable {

    // MEMBERS
    /// @notice  Returns the name of the token.
    string public name;

    /// @notice  Returns the symbol of the token.
    string public symbol;

    /// @notice  Returns the number of decimals the token uses.
    uint8 public decimals;

    // CONSTRUCTOR
    constructor(
        string memory _name,
        string memory _symbol,
        uint8 _decimals,
        address _custodian
    )
        ERC20ImplUpgradeable(_custodian)
        public
    {
        name = _name;
        symbol = _symbol;
        decimals = _decimals;
    }

    // PUBLIC FUNCTIONS
    // (ERC20Interface)
    /** @notice  Returns the total token supply.
      *
      * @return  the total token supply.
      */
    function totalSupply() public view returns (uint256) {
        return erc20Impl.totalSupply();
    }

    /** @notice  Returns the account balance of another account with an address
      * `_owner`.
      *
      * @return  balance  the balance of account with address `_owner`.
      */
    function balanceOf(address _owner) public view returns (uint256 balance) {
        return erc20Impl.balanceOf(_owner);
    }

    /** @dev Internal use only.
      */
    function emitTransfer(address _from, address _to, uint256 _value) public onlyImpl {
        emit Transfer(_from, _to, _value);
    }

    /** @notice  Transfers `_value` amount of tokens to address `_to`.
      *
      * @dev Will fire the `Transfer` event. Will revert if the `_from`
      * account balance does not have enough tokens to spend.
      *
      * @return  success  true if transfer completes.
      */
    function transfer(address _to, uint256 _value) public returns (bool success) {
        return erc20Impl.transferWithSender(msg.sender, _to, _value);
    }

    /** @notice  Transfers `_value` amount of tokens from address `_from`
      * to address `_to`.
      *
      * @dev  Will fire the `Transfer` event. Will revert unless the `_from`
      * account has deliberately authorized the sender of the message
      * via some mechanism.
      *
      * @return  success  true if transfer completes.
      */
    function transferFrom(address _from, address _to, uint256 _value) public returns (bool success) {
        return erc20Impl.transferFromWithSender(msg.sender, _from, _to, _value);
    }

    /** @dev Internal use only.
      */
    function emitApproval(address _owner, address _spender, uint256 _value) public onlyImpl {
        emit Approval(_owner, _spender, _value);
    }

    /** @notice  Allows `_spender` to withdraw from your account multiple times,
      * up to the `_value` amount. If this function is called again it
      * overwrites the current allowance with _value.
      *
      * @dev  Will fire the `Approval` event.
      *
      * @return  success  true if approval completes.
      */
    function approve(address _spender, uint256 _value) public returns (bool success) {
        return erc20Impl.approveWithSender(msg.sender, _spender, _value);
    }

    /** @notice Increases the amount `_spender` is allowed to withdraw from
      * your account.
      * This function is implemented to avoid the race condition in standard
      * ERC20 contracts surrounding the `approve` method.
      *
      * @dev  Will fire the `Approval` event. This function should be used instead of
      * `approve`.
      *
      * @return  success  true if approval completes.
      */
    function increaseApproval(address _spender, uint256 _addedValue) public returns (bool success) {
        return erc20Impl.increaseApprovalWithSender(msg.sender, _spender, _addedValue);
    }

    /** @notice  Decreases the amount `_spender` is allowed to withdraw from
      * your account. This function is implemented to avoid the race
      * condition in standard ERC20 contracts surrounding the `approve` method.
      *
      * @dev  Will fire the `Approval` event. This function should be used
      * instead of `approve`.
      *
      * @return  success  true if approval completes.
      */
    function decreaseApproval(address _spender, uint256 _subtractedValue) public returns (bool success) {
        return erc20Impl.decreaseApprovalWithSender(msg.sender, _spender, _subtractedValue);
    }

    /** @notice  Returns how much `_spender` is currently allowed to spend from
      * `_owner`'s balance.
      *
      * @return  remaining  the remaining allowance.
      */
    function allowance(address _owner, address _spender) public view returns (uint256 remaining) {
        return erc20Impl.allowance(_owner, _spender);
    }
}

/** @title  ERC20 compliant token balance store.
  *
  * @notice  This contract serves as the store of balances, allowances, and
  * supply for the ERC20 compliant token. No business logic exists here.
  *
  * @dev  This contract contains no business logic and instead
  * is the final destination for any change in balances, allowances, or token
  * supply. This contract is upgradeable in the sense that its custodian can
  * update the `erc20Impl` address, thus redirecting the source of logic that
  * determines how the balances will be updated.
  *
  */
contract ERC20Store is ERC20ImplUpgradeable {

    // MEMBERS
    /// @dev  The total token supply.
    uint256 public totalSupply;

    /// @dev  The mapping of balances.
    mapping (address => uint256) public balances;

    /// @dev  The mapping of allowances.
    mapping (address => mapping (address => uint256)) public allowed;

    // CONSTRUCTOR
    constructor(address _custodian) ERC20ImplUpgradeable(_custodian) public {
        totalSupply = 0;
    }

    // PUBLIC FUNCTIONS
    // (ERC20 Ledger)

    /** @notice  The function to set the total supply of tokens.
      *
      * @dev  Intended for use by token implementation functions
      * that update the total supply. The only authorized caller
      * is the active implementation.
      *
      * @param _newTotalSupply the value to set as the new total supply
      */
    function setTotalSupply(
        uint256 _newTotalSupply
    )
        public
        onlyImpl
    {
        totalSupply = _newTotalSupply;
    }

    /** @notice  Sets how much `_owner` allows `_spender` to transfer on behalf
      * of `_owner`.
      *
      * @dev  Intended for use by token implementation functions
      * that update spending allowances. The only authorized caller
      * is the active implementation.
      *
      * @param  _owner  The account that will allow an on-behalf-of spend.
      * @param  _spender  The account that will spend on behalf of the owner.
      * @param  _value  The limit of what can be spent.
      */
    function setAllowance(
        address _owner,
        address _spender,
        uint256 _value
    )
        public
        onlyImpl
    {
        allowed[_owner][_spender] = _value;
    }

    /** @notice  Sets the balance of `_owner` to `_newBalance`.
      *
      * @dev  Intended for use by token implementation functions
      * that update balances. The only authorized caller
      * is the active implementation.
      *
      * @param  _owner  The account that will hold a new balance.
      * @param  _newBalance  The balance to set.
      */
    function setBalance(
        address _owner,
        uint256 _newBalance
    )
        public
        onlyImpl
    {
        balances[_owner] = _newBalance;
    }

    /** @notice Adds `_balanceIncrease` to `_owner`'s balance.
      *
      * @dev  Intended for use by token implementation functions
      * that update balances. The only authorized caller
      * is the active implementation.
      * WARNING: the caller is responsible for preventing overflow.
      *
      * @param  _owner  The account that will hold a new balance.
      * @param  _balanceIncrease  The balance to add.
      */
    function addBalance(
        address _owner,
        uint256 _balanceIncrease
    )
        public
        onlyImpl
    {
        balances[_owner] = balances[_owner] + _balanceIncrease;
    }
}

/** @title  ERC20 compliant token intermediary contract holding core logic.
  *
  * @notice  This contract serves as an intermediary between the exposed ERC20
  * interface in ERC20Proxy and the store of balances in ERC20Store. This
  * contract contains core logic that the proxy can delegate to
  * and that the store is called by.
  *
  * @dev  This contract contains the core logic to implement the
  * ERC20 specification as well as several extensions.
  * 1. Changes to the token supply.
  * 2. Batched transfers.
  * 3. Relative changes to spending approvals.
  * 4. Delegated transfer control ('sweeping').
  *
  */
contract ERC20Impl is CustodianUpgradeable {

    // TYPES
    /// @dev  The struct type for pending increases to the token supply (print).
    struct PendingPrint {
        address receiver;
        uint256 value;
    }

    // MEMBERS
    /// @dev  The reference to the proxy.
    ERC20Proxy public erc20Proxy;

    /// @dev  The reference to the store.
    ERC20Store public erc20Store;

    /// @dev  The sole authorized caller of delegated transfer control ('sweeping').
    address public sweeper;

    /** @dev  The static message to be signed by an external account that
      * signifies their permission to forward their balance to any arbitrary
      * address. This is used to consolidate the control of all accounts
      * backed by a shared keychain into the control of a single key.
      * Initialized as the concatenation of the address of this contract
      * and the word "sweep". This concatenation is done to prevent a replay
      * attack in a subsequent contract, where the sweeping message could
      * potentially be replayed to re-enable sweeping ability.
      */
    bytes32 public sweepMsg;

    /** @dev  The mapping that stores whether the address in question has
      * enabled sweeping its contents to another account or not.
      * If an address maps to "true", it has already enabled sweeping,
      * and thus does not need to re-sign the `sweepMsg` to enact the sweep.
      */
    mapping (address => bool) public sweptSet;

    /// @dev  The map of lock ids to pending token increases.
    mapping (bytes32 => PendingPrint) public pendingPrintMap;

    /// @dev The map of blocked addresses.
    mapping (address => bool) public blocked;

    // CONSTRUCTOR
    constructor(
          address _erc20Proxy,
          address _erc20Store,
          address _custodian,
          address _sweeper
    )
        CustodianUpgradeable(_custodian)
        public
    {
        require(_sweeper != address(0), "no null value for `_sweeper`");
        erc20Proxy = ERC20Proxy(_erc20Proxy);
        erc20Store = ERC20Store(_erc20Store);

        sweeper = _sweeper;
        sweepMsg = keccak256(abi.encodePacked(address(this), "sweep"));
    }

    // MODIFIERS
    modifier onlyProxy {
        require(msg.sender == address(erc20Proxy), "only ERC20Proxy");
        _;
    }
    modifier onlySweeper {
        require(msg.sender == sweeper, "only sweeper");
        _;
    }


    /** @notice  Core logic of the ERC20 `approve` function.
      *
      * @dev  This function can only be called by the referenced proxy,
      * which has an `approve` function.
      * Every argument passed to that function as well as the original
      * `msg.sender` gets passed to this function.
      * NOTE: approvals for the zero address (unspendable) are disallowed.
      *
      * @param  _sender  The address initiating the approval in a proxy.
      */
    function approveWithSender(
        address _sender,
        address _spender,
        uint256 _value
    )
        public
        onlyProxy
        returns (bool success)
    {
        require(_spender != address(0), "no null value for `_spender`");
        require(blocked[_sender] != true, "_sender must not be blocked");
        require(blocked[_spender] != true, "_spender must not be blocked");
        erc20Store.setAllowance(_sender, _spender, _value);
        erc20Proxy.emitApproval(_sender, _spender, _value);
        return true;
    }

    /** @notice  Core logic of the `increaseApproval` function.
      *
      * @dev  This function can only be called by the referenced proxy,
      * which has an `increaseApproval` function.
      * Every argument passed to that function as well as the original
      * `msg.sender` gets passed to this function.
      * NOTE: approvals for the zero address (unspendable) are disallowed.
      *
      * @param  _sender  The address initiating the approval.
      */
    function increaseApprovalWithSender(
        address _sender,
        address _spender,
        uint256 _addedValue
    )
        public
        onlyProxy
        returns (bool success)
    {
        require(_spender != address(0),"no null value for_spender");
        require(blocked[_sender] != true, "_sender must not be blocked");
        require(blocked[_spender] != true, "_spender must not be blocked");
        uint256 currentAllowance = erc20Store.allowed(_sender, _spender);
        uint256 newAllowance = currentAllowance + _addedValue;

        require(newAllowance >= currentAllowance, "new allowance must not be smaller than previous");

        erc20Store.setAllowance(_sender, _spender, newAllowance);
        erc20Proxy.emitApproval(_sender, _spender, newAllowance);
        return true;
    }

    /** @notice  Core logic of the `decreaseApproval` function.
      *
      * @dev  This function can only be called by the referenced proxy,
      * which has a `decreaseApproval` function.
      * Every argument passed to that function as well as the original
      * `msg.sender` gets passed to this function.
      * NOTE: approvals for the zero address (unspendable) are disallowed.
      *
      * @param  _sender  The address initiating the approval.
      */
    function decreaseApprovalWithSender(
        address _sender,
        address _spender,
        uint256 _subtractedValue
    )
        public
        onlyProxy
        returns (bool success)
    {
        require(_spender != address(0), "no unspendable approvals"); // disallow unspendable approvals
        require(blocked[_sender] != true, "_sender must not be blocked");
        require(blocked[_spender] != true, "_spender must not be blocked");
        uint256 currentAllowance = erc20Store.allowed(_sender, _spender);
        uint256 newAllowance = currentAllowance - _subtractedValue;

        require(newAllowance <= currentAllowance, "new allowance must not be smaller than previous");

        erc20Store.setAllowance(_sender, _spender, newAllowance);
        erc20Proxy.emitApproval(_sender, _spender, newAllowance);
        return true;
    }

    /** @notice  Requests an increase in the token supply, with the newly created
      * tokens to be added to the balance of the specified account.
      *
      * @dev  Returns a unique lock id associated with the request.
      * Anyone can call this function, but confirming the request is authorized
      * by the custodian.
      * NOTE: printing to the zero address is disallowed.
      *
      * @param  _receiver  The receiving address of the print, if confirmed.
      * @param  _value  The number of tokens to add to the total supply and the
      * balance of the receiving address, if confirmed.
      *
      * @return  lockId  A unique identifier for this request.
      */
    function requestPrint(address _receiver, uint256 _value) public returns (bytes32 lockId) {
        require(_receiver != address(0), "no null value for `_receiver`");
        require(blocked[msg.sender] != true, "account blocked");
        require(blocked[_receiver] != true, "_receiver must not be blocked");
        lockId = generateLockId();

        pendingPrintMap[lockId] = PendingPrint({
            receiver: _receiver,
            value: _value
        });

        emit PrintingLocked(lockId, _receiver, _value);
    }

    /** @notice  Confirms a pending increase in the token supply.
      *
      * @dev  When called by the custodian with a lock id associated with a
      * pending increase, the amount requested to be printed in the print request
      * is printed to the receiving address specified in that same request.
      * NOTE: this function will not execute any print that would overflow the
      * total supply, but it will not revert either.
      *
      * @param  _lockId  The identifier of a pending print request.
      */
    function confirmPrint(bytes32 _lockId) public onlyCustodian {
        PendingPrint storage print = pendingPrintMap[_lockId];

        // reject ‘null’ results from the map lookup
        // this can only be the case if an unknown `_lockId` is received
        address receiver = print.receiver;
        require (receiver != address(0), "unknown `_lockId`");
        uint256 value = print.value;

        delete pendingPrintMap[_lockId];

        uint256 supply = erc20Store.totalSupply();
        uint256 newSupply = supply + value;
        if (newSupply >= supply) {
          erc20Store.setTotalSupply(newSupply);
          erc20Store.addBalance(receiver, value);

          emit PrintingConfirmed(_lockId, receiver, value);
          erc20Proxy.emitTransfer(address(0), receiver, value);
        }
    }

    /** @notice  Burns the specified value from the sender's balance.
      *
      * @dev  Sender's balanced is subtracted by the amount they wish to burn.
      *
      * @param  _value  The amount to burn.
      *
      * @return success true if the burn succeeded.
      */
    function burn(uint256 _value) public returns (bool success) {
        require(blocked[msg.sender] != true, "account blocked");
        uint256 balanceOfSender = erc20Store.balances(msg.sender);
        require(_value <= balanceOfSender, "disallow burning more, than amount of the balance");

        erc20Store.setBalance(msg.sender, balanceOfSender - _value);
        erc20Store.setTotalSupply(erc20Store.totalSupply() - _value);

        erc20Proxy.emitTransfer(msg.sender, address(0), _value);

        return true;
    }

     /** @notice  Burns the specified value from the balance in question.
      *
      * @dev  Suspected balance is subtracted by the amount which will be burnt.
      *
      * @dev If the suspected balance has less than the amount requested, it will be set to 0.
      *
      * @param  _from  The address of suspected balance.
      *
      * @param  _value  The amount to burn.
      *
      * @return success true if the burn succeeded.
      */
    function burn(address _from, uint256 _value) public onlyCustodian returns (bool success) {
        uint256 balance = erc20Store.balances(_from);
        if(_value <= balance){
            erc20Store.setBalance(_from, balance - _value);
            erc20Store.setTotalSupply(erc20Store.totalSupply() - _value);
            erc20Proxy.emitTransfer(_from, address(0), _value);
            emit Wiped(_from, _value, _value, balance - _value);
        }
        else {
            erc20Store.setBalance(_from,0);
            erc20Store.setTotalSupply(erc20Store.totalSupply() - balance);
            erc20Proxy.emitTransfer(_from, address(0), balance);
            emit Wiped(_from, _value, balance, 0);
        }
        return true;
    }

    /** @notice  A function for a sender to issue multiple transfers to multiple
      * different addresses at once. This function is implemented for gas
      * considerations when someone wishes to transfer, as one transaction is
      * cheaper than issuing several distinct individual `transfer` transactions.
      *
      * @dev  By specifying a set of destination addresses and values, the
      * sender can issue one transaction to transfer multiple amounts to
      * distinct addresses, rather than issuing each as a separate
      * transaction. The `_tos` and `_values` arrays must be equal length, and
      * an index in one array corresponds to the same index in the other array
      * (e.g. `_tos[0]` will receive `_values[0]`, `_tos[1]` will receive
      * `_values[1]`, and so on.)
      * NOTE: transfers to the zero address are disallowed.
      *
      * @param  _tos  The destination addresses to receive the transfers.
      * @param  _values  The values for each destination address.
      * @return  success  If transfers succeeded.
      */
    function batchTransfer(address[] memory _tos, uint256[] memory _values) public returns (bool success) {
        require(_tos.length == _values.length, "_tos and _values must be the same length");
        require(blocked[msg.sender] != true, "account blocked");
        uint256 numTransfers = _tos.length;
        uint256 senderBalance = erc20Store.balances(msg.sender);

        for (uint256 i = 0; i < numTransfers; i++) {
          address to = _tos[i];
          require(to != address(0), "no null values for _tos");
          require(blocked[to] != true, "_tos must not be blocked");
          uint256 v = _values[i];
          require(senderBalance >= v, "insufficient funds");

          if (msg.sender != to) {
            senderBalance -= v;
            erc20Store.addBalance(to, v);
          }
          erc20Proxy.emitTransfer(msg.sender, to, v);
        }

        erc20Store.setBalance(msg.sender, senderBalance);

        return true;
    }

    /** @notice  Enables the delegation of transfer control for many
      * accounts to the sweeper account, transferring any balances
      * as well to the given destination.
      *
      * @dev  An account delegates transfer control by signing the
      * value of `sweepMsg`. The sweeper account is the only authorized
      * caller of this function, so it must relay signatures on behalf
      * of accounts that delegate transfer control to it. Enabling
      * delegation is idempotent and permanent. If the account has a
      * balance at the time of enabling delegation, its balance is
      * also transferred to the given destination account `_to`.
      * NOTE: transfers to the zero address are disallowed.
      *
      * @param  _vs  The array of recovery byte components of the ECDSA signatures.
      * @param  _rs  The array of 'R' components of the ECDSA signatures.
      * @param  _ss  The array of 'S' components of the ECDSA signatures.
      * @param  _to  The destination for swept balances.
      */
    function enableSweep(uint8[] memory _vs, bytes32[] memory _rs, bytes32[] memory _ss, address _to) public onlySweeper {
        require(_to != address(0), "no null value for `_to`");
        require(blocked[_to] != true, "_to must not be blocked");
        require((_vs.length == _rs.length) && (_vs.length == _ss.length), "_vs[], _rs[], _ss lengths are different");

        uint256 numSignatures = _vs.length;
        uint256 sweptBalance = 0;

        for (uint256 i = 0; i < numSignatures; ++i) {
            address from = ecrecover(keccak256(abi.encodePacked("\x19Ethereum Signed Message:\n32",sweepMsg)), _vs[i], _rs[i], _ss[i]);
            require(blocked[from] != true, "_froms must not be blocked");
            // ecrecover returns 0 on malformed input
            if (from != address(0)) {
                sweptSet[from] = true;

                uint256 fromBalance = erc20Store.balances(from);

                if (fromBalance > 0) {
                    sweptBalance += fromBalance;

                    erc20Store.setBalance(from, 0);

                    erc20Proxy.emitTransfer(from, _to, fromBalance);
                }
            }
        }

        if (sweptBalance > 0) {
          erc20Store.addBalance(_to, sweptBalance);
        }
    }

    /** @notice  For accounts that have delegated, transfer control
      * to the sweeper, this function transfers their balances to the given
      * destination.
      *
      * @dev The sweeper account is the only authorized caller of
      * this function. This function accepts an array of addresses to have their
      * balances transferred for gas efficiency purposes.
      * NOTE: any a...

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