// Contract: DigiMiners
// Target function: function toEthSignedMessageHash(bytes memory s)
  /**
   * @dev Transfers ownership of the contract to a new account (`newOwner`).
   * Internal function without access restriction.
   */
  function _transferOwnership(address newOwner) internal virtual {
    address oldOwner = _owner;
    _owner = newOwner;
    emit OwnershipTransferred(oldOwner, newOwner);
  }
}

library Address {
  /**
   * @dev Returns true if `account` is a contract.
   *
   * [IMPORTANT]
   * ====
   * It is unsafe to assume that an address for which this function returns
   * false is an externally-owned account (EOA) and not a contract.
   *
   * Among others, `isContract` will return false for the following
   * types of addresses:
   *
   *  - an externally-owned account
   *  - a contract in construction
   *  - an address where a contract will be created
   *  - an address where a contract lived, but was destroyed
   * ====
   *
   * [IMPORTANT]
   * ====
   * You shouldn't rely on `isContract` to protect against flash loan attacks!
   *
   * Preventing calls from contracts is highly discouraged. It breaks composability, breaks support for smart wallets
   * like Gnosis Safe, and does not provide security since it can be circumvented by calling from a contract
   * constructor.
   * ====
   */
  function isContract(address account) internal view returns (bool) {
    // This method relies on extcodesize/address.code.length, which returns 0
    // for contracts in construction, since the code is only stored at the end
    // of the constructor execution.

    return account.code.length > 0;
  }

  /**
   * @dev Replacement for Solidity's `transfer`: sends `amount` wei to
   * `recipient`, forwarding all available gas and reverting on errors.
   *
   * https://eips.ethereum.org/EIPS/eip-1884[EIP1884] increases the gas cost
   * of certain opcodes, possibly making contracts go over the 2300 gas limit
   * imposed by `transfer`, making them unable to receive funds via
   * `transfer`. {sendValue} removes this limitation.
   *
   * https://diligence.consensys.net/posts/2019/09/stop-using-soliditys-transfer-now/[Learn more].
   *
   * IMPORTANT: because control is transferred to `recipient`, care must be
   * taken to not create reentrancy vulnerabilities. Consider using
   * {ReentrancyGuard} or the
   * https://solidity.readthedocs.io/en/v0.5.11/security-considerations.html#use-the-checks-effects-interactions-pattern[checks-effects-interactions pattern].
   */
  function sendValue(address payable recipient, uint256 amount) internal {
    require(address(this).balance >= amount, "Address: insufficient balance");

    (bool success, ) = recipient.call{value: amount}("");
    require(
      success,
      "Address: unable to send value, recipient may have reverted"
    );
  }

  /**
   * @dev Performs a Solidity function call using a low level `call`. A
   * plain `call` is an unsafe replacement for a function call: use this
   * function instead.
   *
   * If `target` reverts with a revert reason, it is bubbled up by this
   * function (like regular Solidity function calls).
   *
   * Returns the raw returned data. To convert to the expected return value,
   * use https://solidity.readthedocs.io/en/latest/units-and-global-variables.html?highlight=abi.decode#abi-encoding-and-decoding-functions[`abi.decode`].
   *
   * Requirements:
   *
   * - `target` must be a contract.
   * - calling `target` with `data` must not revert.
   *
   * _Available since v3.1._
   */
  function functionCall(address target, bytes memory data)
    internal
    returns (bytes memory)
  {
    return functionCall(target, data, "Address: low-level call failed");
  }

  /**
   * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`], but with
   * `errorMessage` as a fallback revert reason when `target` reverts.
   *
   * _Available since v3.1._
   */
  function functionCall(
    address target,
    bytes memory data,
    string memory errorMessage
  ) internal returns (bytes memory) {
    return functionCallWithValue(target, data, 0, errorMessage);
  }

  /**
   * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],
   * but also transferring `value` wei to `target`.
   *
   * Requirements:
   *
   * - the calling contract must have an ETH balance of at least `value`.
   * - the called Solidity function must be `payable`.
   *
   * _Available since v3.1._
   */
  function functionCallWithValue(
    address target,
    bytes memory data,
    uint256 value
  ) internal returns (bytes memory) {
    return
      functionCallWithValue(
        target,
        data,
        value,
        "Address: low-level call with value failed"
      );
  }

  /**
   * @dev Same as {xref-Address-functionCallWithValue-address-bytes-uint256-}[`functionCallWithValue`], but
   * with `errorMessage` as a fallback revert reason when `target` reverts.
   *
   * _Available since v3.1._
   */
  function functionCallWithValue(
    address target,
    bytes memory data,
    uint256 value,
    string memory errorMessage
  ) internal returns (bytes memory) {
    require(
      address(this).balance >= value,
      "Address: insufficient balance for call"
    );
    require(isContract(target), "Address: call to non-contract");

    (bool success, bytes memory returndata) = target.call{value: value}(data);
    return verifyCallResult(success, returndata, errorMessage);
  }

  /**
   * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],
   * but performing a static call.
   *
   * _Available since v3.3._
   */
  function functionStaticCall(address target, bytes memory data)
    internal
    view
    returns (bytes memory)
  {
    return
      functionStaticCall(target, data, "Address: low-level static call failed");
  }

  /**
   * @dev Same as {xref-Address-functionCall-address-bytes-string-}[`functionCall`],
   * but performing a static call.
   *
   * _Available since v3.3._
   */
  function functionStaticCall(
    address target,
    bytes memory data,
    string memory errorMessage
  ) internal view returns (bytes memory) {
    require(isContract(target), "Address: static call to non-contract");

    (bool success, bytes memory returndata) = target.staticcall(data);
    return verifyCallResult(success, returndata, errorMessage);
  }

  /**
   * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],
   * but performing a delegate call.
   *
   * _Available since v3.4._
   */
  function functionDelegateCall(address target, bytes memory data)
    internal
    returns (bytes memory)
  {
    return
      functionDelegateCall(
        target,
        data,
        "Address: low-level delegate call failed"
      );
  }

  /**
   * @dev Same as {xref-Address-functionCall-address-bytes-string-}[`functionCall`],
   * but performing a delegate call.
   *
   * _Available since v3.4._
   */
  function functionDelegateCall(
    address target,
    bytes memory data,
    string memory errorMessage
  ) internal returns (bytes memory) {
    require(isContract(target), "Address: delegate call to non-contract");

    (bool success, bytes memory returndata) = target.delegatecall(data);
    return verifyCallResult(success, returndata, errorMessage);
  }

  /**
   * @dev Tool to verifies that a low level call was successful, and revert if it wasn't, either by bubbling the
   * revert reason using the provided one.
   *
   * _Available since v4.3._
   */
  function verifyCallResult(
    bool success,
    bytes memory returndata,
    string memory errorMessage
  ) internal pure returns (bytes memory) {
    if (success) {
      return returndata;
    } else {
      // Look for revert reason and bubble it up if present
      if (returndata.length > 0) {
        // The easiest way to bubble the revert reason is using memory via assembly
        /// @solidity memory-safe-assembly
        assembly {
          let returndata_size := mload(returndata)
          revert(add(32, returndata), returndata_size)
        }
      } else {
        revert(errorMessage);
      }
    }
  }
}

library ECDSA {
  enum RecoverError {
    NoError,
    InvalidSignature,
    InvalidSignatureLength,
    InvalidSignatureS,
    InvalidSignatureV
  }

  function _throwError(RecoverError error) private pure {
    if (error == RecoverError.NoError) {
      return; // no error: do nothing
    } else if (error == RecoverError.InvalidSignature) {
      revert("ECDSA: invalid signature");
    } else if (error == RecoverError.InvalidSignatureLength) {
      revert("ECDSA: invalid signature length");
    } else if (error == RecoverError.InvalidSignatureS) {
      revert("ECDSA: invalid signature 's' value");
    } else if (error == RecoverError.InvalidSignatureV) {
      revert("ECDSA: invalid signature 'v' value");
    }
  }

  /**
   * @dev Returns the address that signed a hashed message (`hash`) with
   * `signature` or error string. This address can then be used for verification purposes.
   *
   * The `ecrecover` EVM opcode allows for malleable (non-unique) signatures:
   * this function rejects them by requiring the `s` value to be in the lower
   * half order, and the `v` value to be either 27 or 28.
   *
   * IMPORTANT: `hash` _must_ be the result of a hash operation for the
   * verification to be secure: it is possible to craft signatures that
   * recover to arbitrary addresses for non-hashed data. A safe way to ensure
   * this is by receiving a hash of the original message (which may otherwise
   * be too long), and then calling {toEthSignedMessageHash} on it.
   *
   * Documentation for signature generation:
   * - with https://web3js.readthedocs.io/en/v1.3.4/web3-eth-accounts.html#sign[Web3.js]
   * - with https://docs.ethers.io/v5/api/signer/#Signer-signMessage[ethers]
   *
   * _Available since v4.3._
   */
  function tryRecover(bytes32 hash, bytes memory signature)
    internal
    pure
    returns (address, RecoverError)
  {
    // Check the signature length
    // - case 65: r,s,v signature (standard)
    // - case 64: r,vs signature (cf https://eips.ethereum.org/EIPS/eip-2098) _Available since v4.1._
    if (signature.length == 65) {
      bytes32 r;
      bytes32 s;
      uint8 v;
      // ecrecover takes the signature parameters, and the only way to get them
      // currently is to use assembly.
      /// @solidity memory-safe-assembly
      assembly {
        r := mload(add(signature, 0x20))
        s := mload(add(signature, 0x40))
        v := byte(0, mload(add(signature, 0x60)))
      }
      return tryRecover(hash, v, r, s);
    } else if (signature.length == 64) {
      bytes32 r;
      bytes32 vs;
      // ecrecover takes the signature parameters, and the only way to get them
      // currently is to use assembly.
      /// @solidity memory-safe-assembly
      assembly {
        r := mload(add(signature, 0x20))
        vs := mload(add(signature, 0x40))
      }
      return tryRecover(hash, r, vs);
    } else {
      return (address(0), RecoverError.InvalidSignatureLength);
    }
  }

  /**
   * @dev Returns the address that signed a hashed message (`hash`) with
   * `signature`. This address can then be used for verification purposes.
   *
   * The `ecrecover` EVM opcode allows for malleable (non-unique) signatures:
   * this function rejects them by requiring the `s` value to be in the lower
   * half order, and the `v` value to be either 27 or 28.
   *
   * IMPORTANT: `hash` _must_ be the result of a hash operation for the
   * verification to be secure: it is possible to craft signatures that
   * recover to arbitrary addresses for non-hashed data. A safe way to ensure
   * this is by receiving a hash of the original message (which may otherwise
   * be too long), and then calling {toEthSignedMessageHash} on it.
   */
  function recover(bytes32 hash, bytes memory signature)
    internal
    pure
    returns (address)
  {
    (address recovered, RecoverError error) = tryRecover(hash, signature);
    _throwError(error);
    return recovered;
  }

  /**
   * @dev Overload of {ECDSA-tryRecover} that receives the `r` and `vs` short-signature fields separately.
   *
   * See https://eips.ethereum.org/EIPS/eip-2098[EIP-2098 short signatures]
   *
   * _Available since v4.3._
   */
  function tryRecover(
    bytes32 hash,
    bytes32 r,
    bytes32 vs
  ) internal pure returns (address, RecoverError) {
    bytes32 s = vs &
      bytes32(
        0x7fffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff
      );
    uint8 v = uint8((uint256(vs) >> 255) + 27);
    return tryRecover(hash, v, r, s);
  }

  /**
   * @dev Overload of {ECDSA-recover} that receives the `r and `vs` short-signature fields separately.
   *
   * _Available since v4.2._
   */
  function recover(
    bytes32 hash,
    bytes32 r,
    bytes32 vs
  ) internal pure returns (address) {
    (address recovered, RecoverError error) = tryRecover(hash, r, vs);
    _throwError(error);
    return recovered;
  }

  /**
   * @dev Overload of {ECDSA-tryRecover} that receives the `v`,
   * `r` and `s` signature fields separately.
   *
   * _Available since v4.3._
   */
  function tryRecover(
    bytes32 hash,
    uint8 v,
    bytes32 r,
    bytes32 s
  ) internal pure returns (address, RecoverError) {
    // EIP-2 still allows signature malleability for ecrecover(). Remove this possibility and make the signature
    // unique. Appendix F in the Ethereum Yellow paper (https://ethereum.github.io/yellowpaper/paper.pdf), defines
    // the valid range for s in (301): 0 < s < secp256k1n ÷ 2 + 1, and for v in (302): v ∈ {27, 28}. Most
    // signatures from current libraries generate a unique signature with an s-value in the lower half order.
    //
    // If your library generates malleable signatures, such as s-values in the upper range, calculate a new s-value
    // with 0xFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFEBAAEDCE6AF48A03BBFD25E8CD0364141 - s1 and flip v from 27 to 28 or
    // vice versa. If your library also generates signatures with 0/1 for v instead 27/28, add 27 to v to accept
    // these malleable signatures as well.
    if (
      uint256(s) >
      0x7FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF5D576E7357A4501DDFE92F46681B20A0
    ) {
      return (address(0), RecoverError.InvalidSignatureS);
    }
    if (v != 27 && v != 28) {
      return (address(0), RecoverError.InvalidSignatureV);
    }

    // If the signature is valid (and not malleable), return the signer address
    address signer = ecrecover(hash, v, r, s);
    if (signer == address(0)) {
      return (address(0), RecoverError.InvalidSignature);
    }

    return (signer, RecoverError.NoError);
  }

  /**
   * @dev Overload of {ECDSA-recover} that receives the `v`,
   * `r` and `s` signature fields separately.
   */
  function recover(
    bytes32 hash,
    uint8 v,
    bytes32 r,
    bytes32 s
  ) internal pure returns (address) {
    (address recovered, RecoverError error) = tryRecover(hash, v, r, s);
    _throwError(error);
    return recovered;
  }

  /**
   * @dev Returns an Ethereum Signed Message, created from a `hash`. This
   * produces hash corresponding to the one signed with the
   * https://eth.wiki/json-rpc/API#eth_sign[`eth_sign`]
   * JSON-RPC method as part of EIP-191.
   *
   * See {recover}.
   */
  function toEthSignedMessageHash(bytes32 hash)
    internal
    pure
    returns (bytes32)
  {
    // 32 is the length in bytes of hash,
    // enforced by the type signature above
    return
      keccak256(abi.encodePacked("\x19Ethereum Signed Message:\n32", hash));
  }