hyperlane-monorepo/solidity/contracts/interfaces/IInterchainSecurityModule.sol

// SPDX-License-Identifier: MIT OR Apache-2.0
pragma solidity >=0.6.11;

interface IInterchainSecurityModule {
    enum Types {
        NULL, // used with relayer carrying no metadata
        ROUTING,
        AGGREGATION,
        LEGACY_MULTISIG,
        MERKLE_ROOT_MULTISIG,
        MESSAGE_ID_MULTISIG,
        OPTIMISM
    }

    /**
     * @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);
}

interface ISpecifiesInterchainSecurityModule {
    function interchainSecurityModule()
        external
        view
        returns (IInterchainSecurityModule);
}