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Modular Security

Hyperlane is secured by Interchain Security Modules (ISMs). ISMs are smart contracts that are responsible for verifying that interchain messages being delivered on the destination chain were actually sent on the origin chain.

Hyperlane developers can optionally override the Mailbox's's default ISM by specifying an application-specific ISM, which they can configure, compose, and customize according to the needs of their application.

Configure​

Hyperlane defines a set of pre-built ISMs. Developers can deploy any of these contracts "off-the-shelf" and configure them with their own parameters.

For example, application developers that want increased sovereignty over interchain security could deploy a Multisig ISM configured with validators sourced from their own community.

Compose​

ISMs act as "security legos". Developers can mix and match different ISMs together to encode a security model that best fits their needs.

For example, application developers that want additional security could deploy an Aggregation ISM that requires verification by both a Multisig ISM configured with validators from the Hyperlane community, and a Wormhole ISM that verifies that a quorum of the Wormhole validator set verified the message.

Customize​

ISMs are fully customizable. Developers can write their own ISMs, tailoring them to the needs of their application.

For example, application developers can build ISMs that adjust security models based on message content. High value and infrequent messages (e.g. governance) could be verified by a security model that prioritizes safety over latency and gas costs. Lower value and more frequent messages could be verified by a security model that prioritizes latency and gas costs over safety.

Message recipients can specify custom security constraints by specifying an InterchainSecurityModule address. This implementation can be configured, composed, and customized according to the needs of their application.

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

interface IInterchainSecurityModule {
    enum Types {
        UNUSED,
        ROUTING,
        AGGREGATION,
        LEGACY_MULTISIG,
        MERKLE_ROOT_MULTISIG,
        MESSAGE_ID_MULTISIG,
        NULL, // used with relayer carrying no metadata
        CCIP_READ,
        ARB_L2_TO_L1,
        WEIGHTED_MERKLE_ROOT_MULTISIG,
        WEIGHTED_MESSAGE_ID_MULTISIG,
        OP_L2_TO_L1
    }

    /**
     * @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);
}