Intelligent contract-based license-free interoperation cross-chain protocol generation method and use method

Abstract

The invention discloses a permission-free interoperation cross-chain protocol method based on a smart contract, which comprises the following steps: a message sending module is constructed on a source chain, the message sending module is used for a sender to provide an identity certificate for a repeater, and a mailbox contract is constructed as a transceiving station of a message; interchain message sending and receiving interfaces are respectively disclosed on a source chain and a target chain, a security verification module and a message processing module are constructed on the target chain, a repeater monitors and forwards data in a mailbox contract on the source chain to the security verification module on the target chain, and the security verification module performs security verification processing on the received message data and sends the processed message data to the message processing module. And calling the email contract on the target chain, and delivering the message to a predetermined receiver through a message processing module. According to the method, the receiving and transmitting station with message sending and receiving functions is created by using the intelligent contract on the chain, the mailbox contract is monitored by using the repeater, and the new message is integrated and sent to the target chain after being obtained, so that a set of interoperability cross-chain protocol without permission is realized.

Description

Technical Field

[0001] The present invention relates to cross-chain technology in the field of blockchain, and specifically to a method for generating and using a permissionless interoperable cross-chain protocol based on a smart contract. Background Art

[0002] In recent years, blockchain technology has been fully developed and applied, especially on the public chain. Blockchain networks based on EVM architecture and non-EVM architecture have emerged in an endless stream. The construction of the second-layer network has also greatly alleviated the congestion of the main chain. Based on the popularity of more and more homogeneous and heterogeneous blockchain networks, more and more users need to exchange assets and related on-chain application data between multiple networks.

[0003] At present, the mainstream cross-chain solutions in the market rely on cross-chain bridges to realize the value transfer of data information between blockchains. Cross-chain bridges rely on cross-chain protocols to aggregate data, call smart contracts, and unify asset liquidity. Cross-chain protocols are the basis of all cross-chain operations, which can help two blockchain networks to perform complex transactional message transmission. Mainstream cross-chain protocols usually use a hash-like locking mechanism to lock the assets of the source chain and mint the corresponding assets on the target chain. If the corresponding assets are returned to the source chain across the chain, the corresponding target chain will be destroyed and the source chain will be released.

[0004] However, this cross-chain protocol requires developers to perform complex repeater docking for each new cross-chain demand between two chains, and requires validators on both sides of the cross-chain to support the setting of the cross-chain protocol. This brings a huge workload to developers under the prospect of rapid development of blockchain applications today, and there are also certain constraints on chains with less influence.

[0005] Therefore, there is an urgent need for a permissionless interoperable cross-chain protocol generation method and usage method based on smart contracts to solve the problems of complex docking, large workload, and unfriendly cross-chain for emerging blockchain networks with less influence in the current mainstream blockchain cross-chain protocols. Summary of the invention

[0006] In view of the deficiencies in the prior art, the present invention provides a method for generating and using a permissionless interoperable cross-chain protocol based on a smart contract, so as to solve the problems of the current mainstream blockchain cross-chain protocol, such as complex docking, large workload, and unfriendly cross-chain for emerging blockchain networks with less influence.

[0007] To achieve the above object, the present invention adopts the following technical solutions:

[0008] A method for generating a permissionless interoperable cross-chain protocol based on a smart contract, characterized by comprising the following steps:

[0009] A message sending module is built on the source chain. The message sending module is used to provide identity proof for the repeater responsible for delivering messages on the target chain in the sending direction. A mailbox contract is built as a message sending and receiving station, and API interfaces for sending and receiving messages between chains are publicly disclosed on the source chain and the target chain respectively. A security verification module and a message processing module are built on the target chain. The repeater is used to monitor and forward the data in the mailbox contract on the source chain to the security verification module on the target chain. The security verification module is used to perform security verification on the received message data, call the mailbox contract on the target chain after processing, and deliver the message to the predetermined recipient through the message processing module.

[0010] To optimize the above technical solutions, the specific measures taken also include:

[0011] Furthermore, the security verification module is used to perform security verification processing on the received message data, including the following steps: constructing a metadata processing module in the security verification module on the target chain, and the metadata processing module is used to verify the verified message data after the security verification module performs security verification.

[0012] Furthermore, it also includes: constructing a message monitoring module and a message forwarding module operated by the repeater, the message monitoring module is used to monitor the message data of the mailbox contract on the source chain, and the message forwarding module is used to forward the message data to the security verification module on the target chain.

[0013] Furthermore, it also includes: in the mailbox contract, there are designed a Dispatch function method called by the developer, a Process function method called by the repeater, and a handle function method. The Dispatch function contains all the information required for message sending. The mailbox contract allows the developer to call the Dispatch function method, and is used to mark the message as the task sequence of the target chain after the call. The mailbox contract allows the repeater to call the Process function method, which is used to encapsulate the metadata of the message transmission and the original message data after the repeater is called and send them to the security verification module of the target chain. After the security verification module completes the verification, the handle function method of the mailbox contract on the target chain is called to deliver the message to the predetermined recipient through the message processing module according to the received security verification identifier, the target address and the message content.

[0014] Furthermore, it also includes: configuring a Dispatch hook function callFeeDispatch at the same time.

[0015] Furthermore, the API interface for sending messages in the mailbox contract includes the message content, the ID of the target chain and the address of the recipient as parameters.

[0016] Furthermore, a method for using a permissionless interoperable cross-chain protocol based on a smart contract generated according to the above method comprises the following steps:

[0017] Start the message sending module to send a message, which includes the required message content, destination chain ID and recipient address. The message is sent and stored in the mailbox contract on the source chain. The repeater monitors the mailbox contract on the source chain and forwards the message to the security verification module on the target chain. The security verification module on the target chain receives the message data and performs a security check on the received message data. After verification and approval by the security verification module, the mailbox contract on the target chain is called to deliver the message to the predetermined recipient through the message processing module.

[0018] Furthermore, the repeater monitors the mailbox contract on the source chain and forwards the message to the security verification module on the target chain, including the following steps: constructing a message listening module and a message forwarding module operated by the repeater, monitoring, observing, and processing the message and any metadata defined by the repeater through the message listening module, and forwarding these information data to the security verification module on the target chain through the message forwarding module.

[0019] Furthermore, the following steps are also included: in the mailbox contract, a Dispatch function method called by the developer and a Process function method called by the repeater are designed. The DAPP developer can measure the performance impact of the security algorithm based on business needs, and can select a security policy suitable for the application to inform the security verification module, namely the ICSM module. The ICSM module customizes the security model according to the received security policy, anchors the security policy, and is responsible for collecting data for security verification. When the repeater receives the message through the Process function method, it queries the security policy specified by the DAPP under the corresponding target chain, encapsulates the metadata required for the corresponding policy and sends it to the ICSM module of the target chain. The ICSM module of the target chain adapts the security policy, receives the parameters for security verification, and forwards them to the recipient user of the target chain after verification, thereby realizing inter-chain message transmission of a customized security module.

[0020] Furthermore, the following steps are also included: in the mailbox contract, a handle function method is designed. After the security verification module completes the verification, the handle function method of the mailbox contract on the target chain is called. According to the received security verification identifier, target address and message content, the message is delivered to the predetermined recipient through the message processing module, thereby completing a cross-chain information transmission.

[0021] The beneficial effects of the present invention are:

[0022] The present invention uses on-chain smart contracts to create a transceiver station with the function of sending and receiving messages, uses a repeater to monitor the mailbox contract, integrates identity information and signature information after obtaining new messages, and sends messages to the corresponding target chain, thereby realizing a set of permissionless interoperability cross-chain protocols.

[0023] The present invention can customize the security verification module. By establishing a secure channel between the repeater and the smart contract, after the message is sent by the smart contract of the source chain, the repeater constructs the structured data required by the target chain to receive it. At the same time, the repeater will query the security model required by the target chain. This security model is defined by the target chain itself, and the default security model of the protocol can also be loaded. The repeater constructs metadata according to the corresponding security model to provide verification, so as to carry out inter-chain message transmission of the customized security verification module. This security module can be selected by the application developer according to the needs, so as to maximize the balance between security and application performance.

[0024] The present invention is a permissionless interoperability layer that allows DAPP developers to send arbitrary data between blockchains. Developers can use the cross-chain protocol based on the present invention to perform operations such as function calls, asset transfers, and information transmission. Based on the needs of the application itself, they can select the corresponding ICSM module and balance the security and performance of the application in combination with their own professional knowledge. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 A cross-chain flow chart of a method for using a permissionless interoperable cross-chain protocol based on a smart contract proposed in the present invention;

[0026] Figure 2 This is a message transmission flow chart of a permissionless interoperable cross-chain protocol generation method based on smart contracts proposed in the present invention;

[0027] Figure 3 This is a workflow diagram of a customized security verification module for a method for using a permissionless interoperable cross-chain protocol based on smart contracts proposed in the present invention. DETAILED DESCRIPTION

[0028] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0029] A method for generating a permissionless interoperable cross-chain protocol based on a smart contract according to an embodiment of the present invention comprises the following steps:

[0030] A message sending module is built on the source chain. The message sending module is used to provide identity proof for the repeater responsible for delivering messages on the target chain in the sending direction. A mailbox contract is built as a message sending and receiving station, and API interfaces for sending and receiving messages between chains are publicly disclosed on the source chain and the target chain respectively. A security verification module and a message processing module are built on the target chain. The repeater is used to monitor and forward the data in the mailbox contract on the source chain to the security verification module on the target chain. The security verification module is used to perform security verification on the received message data, call the mailbox contract on the target chain after processing, and deliver the message to the predetermined recipient through the message processing module.

[0031] In a cross-chain scenario, in order to successfully send a message between chains, two transactions are required: one is to send the message from the source chain, and the other is to deliver the message on the target chain. The present invention allows the sender to provide identity proof to the repeater responsible for delivering the message on the target chain through the message sending module built on the source chain, which simplifies the complexity of cross-chain to the greatest extent. By building a mailbox contract as a message transceiver, the message is sent and stored in the mailbox contract on the source chain to assist the proof of stake protocol in completing malicious detection and corresponding punishment. The repeater is responsible for ensuring that the message is delivered to the target chain, and is responsible for observing the mailbox contract of the source chain to monitor whether there are new messages. When a new message is detected, the repeater will query the target chain to determine the inter-chain security verification module of the message recipient, and the security verification module is responsible for verifying whether the cross-chain message transmitted on the target chain is indeed sent on the source chain.

[0032] In essence, the repeater is also a blockchain, which specifies the structure of data exchange between the two chains. The repeater of the present invention exists as a channel for business communication, and the relevant stakeholders participate in its construction as relay nodes to ensure the security of the repeater as a message forwarding middleware and solve the problem of over-centralization of the notary mechanism.

[0033] In this solution, the mailbox contract is used as a message sending and receiving station. It is essentially a smart contract running on the chain. Its purpose is to combine the distributed identity on the chain to promote message transmission between blockchains. Developers can use it to create cross-chain applications and add cross-chain functions to their existing applications. The mailbox contract exposes two API interfaces for sending and receiving messages between chains. Therefore, it is necessary to deploy the mailbox contract on each chain that supports cross-chain. The message sending interface in the mailbox contract contains the message content, the ID of the target chain, and the address of the recipient as parameters. Each message will be incrementally inserted into the DepositMerkle Tree. This is a new feature added by Ethereum 2.0, which makes it easy to ensure that the verifier can safely and quickly verify whether the message source has been modified.

[0034] Among them, the above-mentioned security verification module is used to perform security verification processing on the received message data, including the following steps: constructing a metadata processing module in the security verification module on the target chain, and the metadata processing module is used to verify the verified message data after the security verification module performs security verification.

[0035] Cross-chain messaging is facilitated through the construction of a message listening module, operated by a relayer. It processes the message and any metadata defined by the relayer, forwarding this information to the recipient's inter-chain security module for verification. After approval by this module, the data of the message source is verified through the metadata processing module, and then the mailbox contract delivers the message to the intended recipient through the message processing module.

[0036] It also includes building a message monitoring module and a message forwarding module operated by the repeater. The message monitoring module is used to monitor the message data of the mailbox contract on the source chain, and the message forwarding module is used to forward the message data to the security verification module on the target chain.

[0037] As attached Figure 2 As shown, the mailbox contract is also designed with a Dispatch function method called by developers, a Process function method called by repeaters, and a handle function method. The Dispatch function contains all the information required for message sending. The mailbox contract allows developers to call the Dispatch function method, and is used to mark the message as a task sequence of the target chain after the call. In order to complete the sending of cross-chain transactions, the mailbox contract allows the repeater to call the Process function method, which is used to encapsulate the metadata of the message transmission and the original message data after the repeater is called and send them to the security verification module of the target chain. After the security verification module completes the verification, the handle function method of the mailbox contract on the target chain is called to deliver the message to the predetermined recipient through the message processing module according to the received security verification identifier, the target address and the message content, thereby completing a cross-chain information transmission.

[0038] Among them, a Dispatch hook function callFeeDispatch is also configured. When submitting a transaction to the target chain, a certain fee is often required to be paid for the target chain's security configuration, maintenance and other daily expenses. If the current target chain is configured with callFeeDispatch before calling Dispatch, you need to complete the call of callFeeDispatch first to obtain the current cross-chain transaction fee, and then provide the corresponding fee through the Dispatch function.

[0039] In this solution, two function methods, Dispatch() and Process(), are designed in the mailbox contract, which are called by developers and repeaters respectively. The Dispatch function contains all the information needed to send a message. After calling it, the message is marked as the task sequence of the target chain, and a Dispatch hook function callFeeDispatch() is configured. When submitting a transaction to the target chain, it is often necessary to pay a certain fee for daily expenses such as security configuration and maintenance of the target chain. If the current target chain is configured with callFeeDispatch before calling Dispatch, it is necessary to complete the call of callFeeDispatch first to obtain the current cross-chain transaction fee, and then provide the corresponding fee through the Dispatch function.

[0040] In order to complete the sending of cross-chain transactions, the repeater needs to call the Process method of the contract. The repeater encapsulates the metadata of the message transmission and the original message data and sends them to the security verification module of the target chain. After the module completes the security verification and the identification verification passes, the handle() function of the target chain mailbox contract is called. This function receives the security verification identification, target address, and message content, and sends the message to the specific recipient of the target chain.

[0041] Among them, the API interface for sending messages in the mailbox contract contains the message content, the ID of the target chain and the address of the recipient as parameters. Each message will be incrementally inserted into the Deposit Merkle Tree.

[0042] As attached Figure 1 As shown, a method for using the permissionless interoperable cross-chain protocol based on smart contracts generated according to the above method comprises the following steps:

[0043] Start the message sending module to send a message, which includes the required message content, destination chain ID and recipient address. The message is sent and stored in the incremental Merkle tree of the mailbox contract on the source chain to assist the proof-of-stake protocol in completing malicious detection and corresponding penalties. The repeater monitors the mailbox contract on the source chain and forwards the message to the security verification module on the target chain. The security verification module on the target chain receives the message data and performs security verification on the received message data. After verification and approval by the security verification module, the metadata processing module verifies and processes the data of the message source, and then calls the mailbox contract on the target chain to deliver the message to the predetermined recipient through the message processing module.

[0044] Among them, the above-mentioned repeater monitors the mailbox contract on the source chain and forwards the message to the security verification module on the target chain, including the following steps: constructing a message listening module and a message forwarding module operated by the repeater, monitoring, observing, and processing messages and any metadata defined by the repeater through the message listening module, and forwarding these information data to the security verification module on the target chain through the message forwarding module.

[0045] As attached Figure 3 As shown, the following steps are also included: In the mailbox contract, there are designed Dispatch function methods called by developers and Process function methods called by repeaters. DAPP developers can measure the performance impact of security algorithms according to business needs, and can choose a security policy suitable for the application to inform the security verification module, namely the ICSM module. The ICSM module customizes the security model according to the received security policy, anchors the security policy, and is responsible for collecting data for security verification. When the repeater receives the message through the Process function method, it queries the security policy specified by the DAPP under the corresponding target chain, encapsulates the metadata required by the corresponding policy and sends it to the ICSM module of the target chain. The ICSM module of the target chain adapts the security policy, receives the parameters for security verification, and forwards them to the recipient user of the target chain after verification, so as to realize the inter-chain message transmission of a customized security verification module. Developers can optionally override the default ICSM of the send / receive module by specifying an application-specific ICSM. They can customize the configuration according to the needs of the application, or provide a customized security module.

[0046] In the above scheme, in the ICSM module, the relayer is also responsible for collecting the metadata required by the security module, which will vary depending on the security module and may include signatures from one or more validators, Merkle proofs, zero-knowledge proofs, etc. The security module is essentially a smart contract that is responsible for verifying that the cross-chain message passed on the target chain is indeed sent on the source chain. Developers can optionally override the default security module of the mailbox contract by specifying an application-specific security module, which can be configured, written, and customized according to the needs of the application.

[0047] In order to address the shortcomings of relatively fixed security mechanisms in traditional cross-chain solutions, this solution proposes a modular security component design model, which allows application developers to flexibly configure security modules during the cross-chain process of the two chains, configure them on demand, and maximize the empowerment of blockchain applications.

[0048] Among them, the following steps are also included: in the mailbox contract, a handle function method is designed. After the security verification module completes the verification, the handle function method of the mailbox contract on the target chain is called. According to the received security verification identifier, target address and message content, the message is delivered to the predetermined recipient through the message processing module, thereby completing a cross-chain information transmission.

[0049] A specific implementation of the present invention:

[0050] The protocol of this solution addresses the problems of difficulty, time-consuming and poor security in cross-chain operations between various blockchain networks. It proposes to provide an on-chain interface on the source chain during the cross-chain process to simplify the process of transaction information delivery.

[0051] Set up private keys for deploying smart contracts and relayers.

[0052]

[0053] In the process of preparing the private key, it is necessary to meet the requirements based on the design mechanism of the corresponding chain. It can be a file in pem format or a separate key pair, depending on the underlying blockchain architecture design of both parties across the chain.

[0054] Deploy smart contracts to the local chain and the target chain where the local chain can send and receive messages. There are mainly the following contracts:

[0055] The core contract, including a mailbox that can be used to send and receive messages.

[0056] ICSM can be used to authenticate inbound messages from other local and remote chains.

[0057] A test module contract, to which you send messages to test that everything is working correctly.

[0058] Run a relay. The relay will pass messages between the chains where the contract is deployed.

[0059] Sets the relayer's proxy configuration path.

[0060] Set the chain name of the relay's proxy relay, there may be multiple.

[0061] Set the relayer's private key to sign all chain transactions.

[0062] Send a test message to confirm that the repeater is able to deliver messages to each pair of chains.

[0063] Use the CLI command to send a test message to the test module and wait for the contract to execute. If the message sending timeout occurs, check the relayer settings. The smart contract returns the expected result, indicating that the cross-chain information transfer is completed.

[0064] At the same time, the security design in cross-chain protocols is often difficult to change and depends on the design of the protocol developers. It becomes very difficult for blockchain application developers to make a trade-off between security and performance.

[0065] The present invention is a permissionless interoperability layer that allows DAPP developers to send arbitrary data between blockchains. Developers can use the cross-chain protocol based on the present invention to perform operations such as function calls, asset transfers, and information transmission. Based on the needs of the application itself, they can select the corresponding ICSM module and balance the security and performance of the application in combination with their own professional knowledge.

[0066] The application interacts with the cross-chain protocol through a smart contract called Mailbox, which provides an on-chain messaging interface to send and receive inter-chain messages. At the same time, the present invention adopts a modular approach to achieve security, allowing the application to configure or select the corresponding security module. The application can specify a security module to customize the security model to ensure its integration security with the mailbox contract messaging interface.

[0067] In another embodiment, the present invention proposes a computer-readable storage medium storing a computer program, wherein the computer program enables a computer to execute a method for generating a permissionless interoperable cross-chain protocol based on a smart contract or a method for using a permissionless interoperable cross-chain protocol based on a smart contract as described above.

[0068] In another embodiment, the present invention proposes an electronic device, comprising: a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein when the processor executes the computer program, a method for generating a permissionless interoperable cross-chain protocol based on a smart contract or a method for using a permissionless interoperable cross-chain protocol based on a smart contract as described above is implemented.

[0069] In the embodiments disclosed in the present application, the computer storage medium can be a tangible medium that can contain or store a program for use by or in conjunction with an instruction execution system, device or equipment. The computer storage medium can include, but is not limited to, electronic, magnetic, optical, electromagnetic, infrared, or semiconductor systems, devices or equipment, or any suitable combination of the above. More specific examples of computer storage media can include electrical connections based on one or more lines, portable computer disks, hard disks, random access memories (RAM), read-only memories (ROM), erasable programmable read-only memories (EPROM or flash memory), optical fibers, portable compact disk read-only memories (CD-ROM), optical storage devices, magnetic storage devices, or any suitable combination of the above.

[0070] Those of ordinary skill in the art will appreciate that the units and algorithm steps of each example described in conjunction with the embodiments disclosed in this application can be implemented in electronic hardware or a combination of computer software and electronic hardware. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Professional and technical personnel can use different methods to implement the described functions for each specific application, but such implementation should not be considered to be beyond the scope of this application.

[0071] The above are only preferred embodiments of the present invention, and the protection scope of the present invention is not limited to the above embodiments. All technical solutions under the concept of the present invention belong to the protection scope of the present invention. It should be pointed out that for ordinary technicians in this technical field, some improvements and modifications without departing from the principle of the present invention should be regarded as the protection scope of the present invention.

Claims

1. A permissionless interoperable cross-chain protocol generation method based on smart contracts, characterized in that: The steps include: A message sending module is built on the source chain. The message sending module is used to provide identity proof for the repeater responsible for delivering messages on the target chain in the sending direction. A mailbox contract is built as a message sending and receiving station, and API interfaces for sending and receiving messages between chains are publicly disclosed on the source chain and the target chain respectively. A security verification module and a message processing module are built on the target chain. The repeater is used to monitor and forward the data in the mailbox contract on the source chain to the security verification module on the target chain. The security verification module is used to perform security verification on the received message data, call the mailbox contract on the target chain after processing, and deliver the message to the predetermined recipient through the message processing module.

2. According to claim 1, a permissionless interoperable cross-chain protocol generation method based on smart contracts is characterized in that: The security verification module is used to perform security verification processing on the received message data, including the following steps: constructing a metadata processing module in the security verification module on the target chain, and the metadata processing module is used to verify the verified message data after the security verification module performs security verification.

3. According to claim 1, a permissionless interoperable cross-chain protocol generation method based on smart contracts is characterized in that: Also includes: Construct a message monitoring module and a message forwarding module operated by the repeater. The message monitoring module is used to monitor the message data of the mailbox contract on the source chain, and the message forwarding module is used to forward the message data to the security verification module on the target chain.

4. According to claim 1, a permissionless interoperable cross-chain protocol generation method based on smart contracts is characterized in that: Also includes: In the mailbox contract, there are designed Dispatch function methods called by developers, Process function methods called by repeaters, and handle function methods. The Dispatch function contains all the information required for message sending. The mailbox contract allows developers to call the Dispatch function method, and is used to mark the message as the task sequence of the target chain after the call. The mailbox contract allows the repeater to call the Process function method, which is used to encapsulate the metadata of the message transmission and the original message data after the repeater is called and send them to the security verification module of the target chain. After the security verification module completes the verification, the handle function method of the mailbox contract on the target chain is called to deliver the message to the predetermined recipient through the message processing module according to the received security verification identifier, the target address and the message content.

5. According to claim 4, a method for generating a permissionless interoperable cross-chain protocol based on a smart contract is characterized in that: Also includes: At the same time, a Dispatch hook function callFeeDispatch is configured.

6. According to claim 4, a permissionless interoperable cross-chain protocol generation method based on smart contracts is characterized in that: The API interface for sending messages in the mailbox contract contains the message content, the ID of the target chain and the address of the recipient as parameters.

7. A method for using a permissionless interoperable cross-chain protocol based on a smart contract generated according to any one of claims 1 to 6 above, characterized in that: The steps include: Start the message sending module to send a message, which includes the required message content, destination chain ID and recipient address. The message is sent and stored in the mailbox contract on the source chain. The repeater monitors the mailbox contract on the source chain and forwards the message to the security verification module on the target chain. The security verification module on the target chain receives the message data and performs a security check on the received message data. After verification and approval by the security verification module, the mailbox contract on the target chain is called to deliver the message to the predetermined recipient through the message processing module.

8. A method for using a permissionless interoperable cross-chain protocol based on a smart contract according to claim 7, characterized in that: The repeater monitors the mailbox contract on the source chain and forwards the message to the security verification module on the target chain, including the following steps: constructing a message listening module and a message forwarding module operated by the repeater, monitoring, observing, and processing the message and any metadata defined by the repeater through the message listening module, and forwarding this information data to the security verification module on the target chain through the message forwarding module.

9. A method for using a permissionless interoperable cross-chain protocol based on a smart contract according to claim 7, characterized in that: It also includes the following steps: In the mailbox contract, there are designed Dispatch function methods called by developers and Process function methods called by repeaters. DAPP developers can measure the performance impact of security algorithms based on business needs, and can select security policies suitable for the application to inform the security verification module, namely the ICSM module. The ICSM module customizes the security model based on the received security policy, anchors the security policy, and is responsible for collecting data for security verification. When the repeater receives the message through the Process function method, it queries the security policy specified by the DAPP under the corresponding target chain, encapsulates the metadata required for the corresponding policy and sends it to the ICSM module of the target chain. The ICSM module of the target chain adapts the security policy, receives the parameters for security verification, and forwards them to the recipient user of the target chain after verification, thereby realizing inter-chain message transmission of a customized security module.

10. According to claim 7, a method for using a permissionless interoperable cross-chain protocol based on a smart contract, characterized in that: It also includes the following steps: In the mailbox contract, a handle function method is designed. After the security verification module completes the verification, the handle function method of the mailbox contract on the target chain is called. According to the received security verification identifier, target address and message content, the message is delivered to the predetermined recipient through the message processing module, thereby completing a cross-chain information transmission.

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