Create Your Own ISM

// SPDX-License-Identifier: MIT OR Apache-2.0
pragma solidity >=0.8.0;

enum ModuleType {
UNUSED,
ROUTING,
AGGREGATION,
LEGACY_MULTISIG,
MERKLE_ROOT_MULTISIG,
MESSAGE_ID_MULTISIG,
NULL, // used with relayer carrying no metadata
CCIP_READ,
ARB_L2_TO_L1,
POLYGON_POS,
OP_STACK
}

interface InterchainSecurityModule {
/\*\*
_ @notice Returns an enum that represents the type of security model
_ encoded by this ISM.
_ @dev Relayers infer how to fetch and format metadata.
_/
function moduleType() external view returns (uint8);

    /**
     * @notice Defines a security model responsible for verifying interchain
     * messages based on the provided metadata.
     * @param _metadata Off-chain metadata provided by a relayer, specific to
     * the security model encoded by the module (e.g. validator signatures)
     * @param _message Hyperlane encoded interchain message
     * @return True if the message was verified
     */
    function verify(
        bytes calldata _metadata,
        bytes calldata _message
    ) external returns (bool);

}