CN111666323A

CN111666323A - Cross-chain intercommunication method and system for block chain

Info

Publication number: CN111666323A
Application number: CN202010414373.9A
Authority: CN
Inventors: 樊家合; 陈昌; 杨文韬
Original assignee: Xi'an Zhigui Internet Technology Co ltd
Current assignee: Xi'an Zhigui Internet Technology Co ltd
Priority date: 2020-05-15
Filing date: 2020-05-15
Publication date: 2020-09-15
Anticipated expiration: 2040-05-15
Also published as: CN111666323B

Abstract

The invention provides a cross-chain interconnection method and a cross-chain interconnection system for a block chain. The method for interconnecting the block chains in a cross-chain mode comprises the following steps: determining a block chain interconnection theoretical model according to the block chain and the cross-chain requirements of the block chain; based on the block chain interconnection theoretical model, obtaining an inter-chain interoperation protocol of block chain interconnection; creating a cross-chain distributed application according to a preset rule; and performing chain-crossing operation between two preset block chains through the chain-crossing distributed application to perform function verification and protocol evaluation on the block chain interconnection and intercommunication theoretical model, so as to realize optimization of the block chain interconnection and intercommunication theoretical model. The cross-chain interconnection method of the block chains can conveniently, safely and reliably realize cross-chain interconnection between the block chains, and can effectively reduce the reconstruction of the block chains particularly when the heterogeneous block chains are interconnected, thereby reducing the cost of cross-chain operation.

Description

Cross-chain intercommunication method and system for block chain

Technical Field

The invention relates to the technical field of communication, in particular to a cross-chain interconnection method and a cross-chain interconnection system for a block chain.

Background

From the development process of the blockchain, the interconnection and interworking between blockchain systems become the primary problem restricting the development of blockchain technology. Since the head blockchain system does not exhibit the ability of one chain to control all and applicable scenarios, a blockchain multi-chain closed concurrent scheme is gradually formed. At present, the block chain cross-chain technical scheme is mainly divided into the following steps according to different specific implementation modes: notary mechanisms, side chains, relays, hash locks, distributed private key control, atomic interchange protocols, bridging techniques, chain links, and the like.

However, there is no generally accepted cross-chain mechanism, and the technical difficulties of interconnection and intercommunication of the blockchain system include cross-chain transaction verification problem, cross-chain transaction management problem, locked asset management problem, multi-chain protocol adaptation problem, cross-chain security guarantee problem, and the like. Thus, cross-chain interconnection is constrained.

Disclosure of Invention

Based on the problems in the prior art, the invention provides a method and a system for cross-chain intercommunication of a block chain. The cross-chain interconnection and intercommunication method of the block chains can conveniently, safely and reliably realize cross-chain interconnection and intercommunication among the block chains.

In a first aspect, the present invention provides a method for cross-chain interworking of block chains, including:

determining a block chain interconnection theoretical model according to the block chain and the cross-chain requirements of the block chain;

based on the block chain interconnection theoretical model, obtaining an inter-chain interoperation protocol of block chain interconnection;

creating a cross-chain distributed application according to a preset rule;

and performing chain-crossing operation between two preset block chains through the chain-crossing distributed application to perform function verification and protocol evaluation on the block chain interconnection and intercommunication theoretical model, so as to realize optimization of the block chain interconnection and intercommunication theoretical model.

In a second aspect, the present invention provides a block chain cross-chain interconnection system, including:

the determining module is used for determining the block chain interconnection theoretical model according to the block chain and the cross-chain requirements of the block chain;

the protocol design module is used for obtaining an inter-chain interoperation protocol of the block chain interconnection and intercommunication based on the block chain interconnection and intercommunication theoretical model;

the application creation module is used for creating the cross-chain distributed application according to a preset rule;

and the optimization module is used for performing chain-crossing operation between two preset block chains through the chain-crossing distributed application so as to perform function verification and protocol evaluation on the block chain interconnection and intercommunication theoretical model and realize optimization on the block chain interconnection and intercommunication theoretical model.

In a third aspect, the present invention provides a non-transitory computer readable storage medium having stored thereon a computer program which, when executed by a processor, implements the method for cross-chain interconnection of blockchains according to the first aspect described above.

One or more technical solutions in the embodiments of the present invention have at least one of the following technical effects:

according to the embodiment of the invention, cross-chain intercommunication interconnection among the block chains can be conveniently, safely and reliably realized, and particularly, when intercommunication interconnection is carried out among heterogeneous block chains, the transformation of the block chains can be effectively reduced, so that the cost of cross-chain operation is reduced.

Additional aspects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to these drawings without creative efforts.

Fig. 1 is a flowchart of a cross-chain interconnection method for a blockchain according to an embodiment of the present invention;

fig. 2 is a schematic diagram of a technical implementation framework of a block chain cross-chain interconnection method according to an embodiment of the present invention;

fig. 3 is a schematic diagram of an analysis content framework of a block chain cross-chain interconnection method according to an embodiment of the present invention;

fig. 4 is a block chain interconnection and interworking protocol framework diagram of a cross-chain interconnection method of a block chain according to an embodiment of the present invention;

fig. 5 is a block diagram of a cross-chain interconnection system of a blockchain according to an embodiment of the present invention.

Detailed Description

The following further describes embodiments of the present invention with reference to the accompanying drawings. The following examples are only for illustrating the technical solutions of the present invention more clearly, and the protection scope of the present invention is not limited thereby.

The following describes a method and a system for interconnecting block chains across chains according to an embodiment of the present invention with reference to the accompanying drawings.

Before describing a cross-chain interconnection method for removing cross-chains according to an embodiment of the present invention, a current cross-chain problem is first explained.

The cross-chain technology is a main mode for solving the interconnection problem of the block chain system. Cross-chaining techniques are used for inter-communication in a block chaining system, like TCP/IP is used for the Internet. The cross-chain technology is a technology which can make value cross the barriers between chains and carry out direct circulation. The cross-chain interaction can be divided into homogeneous chain cross-chain and heterogeneous chain cross-chain according to different underlying technology platforms of the crossed block chain. The safety mechanism, the consensus algorithm, the network landslide and the block generation verification logic among the isomorphic chains are the same, and the cross-chain interaction among the isomorphic chains is relatively simple; the cross-chain interaction of the heterogeneous chain is relatively complex, the block composition form and the certainty guarantee mechanism of the block are greatly different, and the direct cross-chain interaction mechanism is not easy to design.

The current block chain cross-chain technical scheme is mainly divided into the following steps according to different specific implementation modes: notary mechanisms, side chains, relays, hash locks, distributed private key control, atomic interchange protocols, bridging techniques, chain links, and the like.

However, there is no generally accepted cross-link mechanism, and the technical difficulties of inter-connection of blockchain systems (i.e. blockchain) include the following five aspects:

cross-chain transaction verification problem:

the interconnection and intercommunication among the blockchains are realized, and a trust mechanism among blockchain systems is designed primarily, so that one blockchain can receive and verify the transaction on the other blockchain. The confirmation and verification of the transaction involves two problems, namely, confirming that the transaction has occurred and writing the transaction into a blockchain ledger; the second is to verify that the transaction has been confirmed by enough nodes in the system. The current common cross-chain transaction verification mechanism comprises a notary mechanism and a block header + SPV mode. The notary mechanism verifies the reliability of the cross-link message through an external notary, and the notary needs to sign the cross-link message after verification. The block head + SPV mode is to store block head data of the external block chain system provided by the notary in its own network, and verify the transaction according to the SPV mechanism.

Cross-chain transaction management problem:

a complete cross-chain transaction can be divided into a plurality of sub-transactions, each sub-transaction is processed in the block chain system to which the sub-transaction belongs, the sub-transactions form a transaction, and cross-chain transaction management is needed to ensure the consistency and atomicity of the transaction. The cross-chain transaction management is divided into two sub-problems, namely a final certainty problem of the transaction and an atomicity problem of the transaction. In cross-chain transaction management, to ensure the final certainty of a transaction, there are generally three schemes: waiting for enough confirmation numbers, block entanglement and using a consensus algorithm such as DPoS or BFT. Waiting for a sufficient number of acknowledgements is the simplest and crudely approach, with the disadvantage that the transaction time becomes longer. The principle of block entanglement is to make the blocks of two chains have dependency relationship, and when a block on one chain is revoked, the related blocks on the other chain are automatically revoked. Compared with a PoW consensus algorithm, the final certainty is easier to achieve by the consensus algorithms such as DPoS or BFT, and the block chain system using the consensus algorithms can efficiently achieve cross-chain transactions. The atomicity of the transaction is a basic requirement for realizing the cross-chain transaction and is a difficult point which must be solved by the cross-chain transaction.

Locking asset management issues:

bidirectional anchoring is the process of bidirectional transfer of assets on the main and side chains in a 1:1 exchange ratio. The key issue in the bi-directional anchoring design is who manages the locked account and performs locking and unlocking operations, and how to ensure that the locked asset is safely released without creating a double-flower problem. In addition, it is equally important how to ensure that the total amount of assets in both chains is constant. With regard to the management of asset locks, there are currently a single custodian mode, a federated custodian mode, and a smart contract mode. The single host mode is that a single host is responsible for managing the locked assets, executing and supervising the unlocking operation of the locked assets. The single custodian model, while simple and easy, is too dependent on a centralized custodian. The more decentralized mode is the federation hosting mode, when a cross-link unlock request is received, the N notaries in the federation all trade independently and vote, and when the number of votes reaches a threshold M, the locked asset can be disposed. The intelligent contract mode is for further decentralization, and the scheme is premised on the fact that the blockchain system can support intelligent contracts and can store the blockheads of the external blockchains to verify external transaction data.

Multi-chain protocol adaptation problem:

with the development and continuous landing of block chain technology, a block chain ecosystem is inevitably an ecosystem with multiple chains coexisting and interconnecting in the future. The multi-chain interconnection and intercommunication implies two layers of meanings, namely how the existing block chain realizes interconnection and intercommunication; and secondly, for the block chain to be developed, how to lay and prepare for interconnection and intercommunication of the block chain. Thus, the multi-chain cross-chain scheme can be classified into an active compatible type and a passive compatible type scheme. The active compatible scheme is performed from top to bottom, mainly aiming at the existing block chain system, the block chain application system with different upper layers is firstly performed, and the cross-chain mechanism development of the bottom layer is performed. The existing block chain system is heterogeneous chain, and needs to be butted one by one. The passive compatible scheme is designed from bottom to top, mainly aiming at an undeveloped block chain system, a bottom-layer chain spanning platform is set up at first, then a new block chain system is developed based on the chain spanning platform, or the existing block chain system is simply, conveniently and safely accessed to the platform, and the system sharing the chain spanning platform is convenient.

The problem of chain-crossing safety guarantee:

when two systems interact, the two systems inevitably affect each other, and if the inter-chain security cannot be isolated, if one chain is attacked, the whole cross-chain network is affected. How to guarantee the safety of the self system and the opposite system in the cross-chain transaction process is a considerable problem. In general, the following three aspects can be considered: moderate isolation, detection of security events, and assurance of correctness of cross-chain transactions. The chains should maintain respective independence, and cross-chain transactions are processed through a third-party node or an independent module as much as possible, so that when a problem occurs in the cross-chain transactions, the processing of the transactions of the chains cannot be influenced. If the third party node or independent module has the capability of detecting security events and the capability of responding, the method is further based on the isolation of the system architecture, so that the cross-link protocol or system has the function similar to a firewall.

Fig. 1 shows a flowchart of a method for interconnecting block chains across chains according to an embodiment of the present invention, and as shown in fig. 1, the method for interconnecting block chains across chains according to an embodiment of the present invention includes the following steps:

s101: and determining a block chain interconnection theoretical model according to the block chain and the cross-chain requirements of the block chain. For example: and analyzing the block chain and the cross-chain requirement of the block chain to abstract out a block chain interconnection theoretical model.

S102: and obtaining an inter-chain interoperation protocol of block chain interconnection and intercommunication based on the block chain interconnection and intercommunication theoretical model.

Specifically, a block chain interconnection and interworking theoretical model is taken as a guide to obtain inter-chain interoperation protocols and related mechanisms of block chain interconnection and interworking, wherein the related mechanisms comprise a cross-chain transaction verification mechanism, a cross-chain security management mechanism and a uniform programming language of a cross-chain intelligent contract. The safety of the block chain interconnection theoretical model needs to meet the safety of the UC safety framework.

In an embodiment of the present invention, an inter-chain interoperation protocol for interconnection and interworking of block chains includes four sub-protocols and two phases, where the four sub-protocols include a protocol implemented by a client, a protocol implemented by a transaction execution system, a protocol implemented by a network state system, and a protocol implemented by a transaction guarantee intelligent contract, and the two phases are a program execution phase and an insurance pursuit phase, respectively, where in the program execution phase, a transaction in an executable program needs to be submitted to a corresponding block chain. During the insurance compensation phase, the correctness of the program execution is arbitrated.

In addition, encryption can be carried out between the client and the transaction execution system according to a preset password protocol.

S103: and creating the cross-chain distributed application according to preset rules. For example: the cross-chain distributed application is developed using a unified state model and a unified programming language.

S104: the cross-chain operation is carried out between two preset block chains through cross-chain distributed application, so that the block chain interconnection and intercommunication theoretical model is subjected to function verification and protocol evaluation, and the block chain interconnection and intercommunication theoretical model is optimized. Therefore, the optimized block chain interconnection theoretical model can be used as a reference for realizing a general reference conceptual model and a key technology prototype of cross-chain interconnection of the block chain, and further, the cross-chain interconnection of the block chain can be simply and conveniently realized by utilizing the general reference conceptual model and the key technology prototype.

Through the above S101 to S104, the actual development conditions of the block chain technology can be closely related, the general interconnection and intercommunication technologies of various block chains are concerned, key problems such as cross-chain transaction verification, cross-chain transaction management, cross-chain multi-protocol adaptation, cross-chain security guarantee and the like in the interconnection and intercommunication of the block chain system are considered, and a theoretical model (i.e., a theoretical model for block chain interconnection and intercommunication) of the block chain system and a prototype system (i.e., cross-chain distributed application) of the block chain interconnection and intercommunication are researched from the perspective of theoretical model abstraction and software engineering realization. In a specific example, a block chain test environment with terminal as an engine and a test environment of an alliance chain hyper-hedge Fabric block chain are established, cross-chain operation is performed around a prototype system and the two chains, block chain interconnection and intercommunication model function verification and protocol evaluation are carried out, and therefore a general reference concept model and key technology prototype implementation for solving the block chain interconnection and intercommunication key problem are provided.

Specifically, through analysis of key technologies of interconnection and interworking of the blockchain system, a universal cross-chain interoperability protocol is designed, and interoperability and programmability between heterogeneous blockchains are simultaneously met, including:

(1) and a programming framework and a matched tool set are provided, and the development of cross-chain distributed application is facilitated. Through abstraction, a virtual layer is provided on different underlying heterogeneous blockchains to shield the heterogeneity and complexity of the underlying blockchains, and a uniform state model and a programming language are used for describing and developing the cross-chain distributed application. Under this framework, developers can easily develop cross-chain distributed applications that do not require implementation of cryptographic security protocols.

(2) The inter-chain interoperation protocol is designed, is a universal cross-chain protocol, and can be used in a range of covering the exchange of digital assets and supporting generalized data exchange. The inter-chain interoperation protocol can realize complex cross-chain operation related to intelligent contract calling on different blockchain networks, and ensure the security of the complex cross-chain calling. The ideal function is used to represent the security attribute of the inter-chain interoperability protocol, and the UC security framework is used to prove that the inter-chain interoperability protocol implements the ideal function.

(3) And developing a system prototype, and verifying and evaluating the prototype system by using two different cross-chain distributed applications.

In technical implementation, the interconnection and interworking problem of the block chain greatly limits the application space of the block chain technology. Aiming at the problem, the invention expands the analysis of the key technology of interconnection and intercommunication of the block chains. As shown in fig. 2, includes: theoretical analysis, cross-chain technology research, prototype development, experimental evaluation and scene application.

In the theoretical analysis, the interconnection and intercommunication problem of the block chain is abstracted into a general concept model according to the basic theories of a state machine, language compilation, a safety framework and the like, a formal language is operated, and analysis activities such as formal specification description, model reasoning, verification and the like are carried out. The interconnection problem of the block chain can be abstracted to the interconnection problem under the Internet architecture, and the interconnection models of different block chain networks are built by using the connectors, the routers and the bridges. An existing abstract model is a cross-chain asset transfer model implemented based on a payment channel and a payment channel network. And a general model based on a state machine is adopted, the block chains are regarded as mutually independent state machine networks, the interconnection and intercommunication provides the execution of an intelligent contract through a distributed state machine, and the state transfer is realized on different block chains. Theoretically, whether the atomic exchange protocol or the inter-chain crossing protocol conforms to the forward transaction from one blockchain to another blockchain, or the backward transaction, or the bidirectional transaction, and can be represented by using a graph model.

In the cross-chain technology research, the existing research literature of block chain interconnection and intercommunication is researched and sorted, the common attributes of the problems researched by the research literature are summarized, and the research thought, the research method and the research result are analyzed and contrasted. Selecting typical engineering projects for solving the interconnection and intercommunication problem of the block chains, analyzing and summarizing the functional characteristics, system design and code implementation of the typical engineering projects from the perspective of software engineering, and summarizing the key technology and the advantages and disadvantages of the typical projects.

In the prototype development, the specific connotations of interconnection and intercommunication are clarified through the recognization and the redefinition of cross-chain concepts, and the properties, the relations and the operations of the concepts are specified. On the basis of concepts and general models, specific details of each protocol and module are designed, and a programming language development system prototype is selected.

In the experiment evaluation, a source code of the prototype system is compiled into an executable program, the executable program is deployed in a test environment, a client or a wallet system is used for sending cross-chain transaction, the prototype system is subjected to function test and performance test according to different scenes and test cases, and the correctness of the execution of the cross-chain transaction of the detection system is evaluated; counting system performance test indexes, and inspecting system transaction delay and performance conditions; and simulating block chain malicious attack and evaluating the safety of the prototype system.

In the scenario application, the application scenario of the cross-chain comprises asset transfer, asset exchange, asset retention, a cross-chain intelligent contract and a cross-chain prediction machine. The functions of a cross-chain intelligent contract and a prediction machine are used, and scene application exploration is developed by combining specific services of guarantee fund, option transaction, financial derivative innovation and the like of financial transaction.

In research content, the interconnection and intercommunication among the block chains is to realize the circulation of information, data and value among the chains. Theoretically, the method comprises the contents of abstract of general problems, description and reasoning of formal languages, analysis of formal security attributes and the like. In terms of engineering implementation, the method relates to aspects such as inter-chain communication protocols, cross-chain data exchange protocols, cross-chain transaction verification, cross-chain security governance, cross-chain intelligent contract application development and the like. The project aims to abstract out a general conceptual model through analysis of a block chain and cross-chain requirements of the block chain. Based on the guidance of a general concept model, modules such as a cross-chain protocol, a cross-chain transaction verification mechanism, a cross-chain safety governance mechanism, a cross-chain intelligent contract programming language and the like are designed, a block chain network prototype with interoperability and programmability is constructed, and theoretical inspection and prototype evaluation are realized.

In order to solve the problem of interconnection and intercommunication among block chain systems, the invention starts from the aspects of theoretical research and software engineering, adopts a thinking path from concrete to abstract to concrete, and researches three aspects of analysis of a block chain interconnection and intercommunication theoretical model, design and realization of a block chain interconnection and intercommunication universal protocol, a cross-chain distributed application compiling technology and the like. The logical relationship is schematically shown in fig. 3.

And analyzing a block chain interconnection theory model: blockchain interworking is the combination of different blockchain systems, each representing a distributed data book, wherein transaction execution may span multiple blockchain systems, wherein data recorded in a blockchain may be retrieved and validated by another transaction from outside, possibly in a semantically compatible manner.

The interconnection and intercommunication of the block chain are required in many different scenes, from the perspective of high-level application, the interconnection and intercommunication application scene is expanded from finance to identity authentication, and numerous different application scenes can embody the interconnection and intercommunication value of the block chain. From the standpoint of computational theory, different types of interconnection and intercommunication scenes can be simply classified and uniformly defined as a causal effect graph model. Specifically, there are three types of models: forward causal, reverse causal and dependent causal. These three types essentially reveal the causal relationship of transaction order and state changes between different blockchains. These three types do not occur simultaneously in the actual application scenario. From the aspect of logic relationship, interconnection is essentially a reliable and stable causal relationship of state changes caused by events in different blockchain systems.

Wherein, a forward cause and effect can describe that chain a can trigger an event on chain B to occur, equivalently to say that chain B can read the data of chain a. An inverse causality is that chain B can trigger an event on chain a, the event occurring in the opposite sense. Dependent causality refers to the occurrence of events that change the state of chain C triggers chain A and chain B simultaneously, which simultaneously generate dependency on the state data of chain C.

The relay cross-chain mechanism provides two cross-chain interaction types of forward cause and reverse cause, and different relay chain implementations may have different capabilities. A cross-chain implementation of the notary mechanism may provide any of these three. The hash lock chaining mechanism provides for the execution of a dependent causal model by the presentation of hash values as a common cause. After the three causal effect models are available, the complex situations which can be calculated and explained can be deduced according to the equivalent transformation of the three causal effect models and the combination of the models. The equivalent transformation of the three causal effect models is equivalent transformation among three mechanisms of exploration relay, notary and Hash locking, and theoretical basis is provided for the optimization design of the mechanisms. The combination of the three models is to use the three basic models to solve the maximum set of usage scenarios, and to explore a method for reducing cross-link complexity in complex scenarios, such as adopting a high-level cross-link programming language (conditional event sending and interception mechanism) to express the concerns of different aspects of interconnection and intercommunication problems, and to provide theoretical guidance for cross-link engineering implementation.

It is understood from a mathematical logic point of view that the forward causal model can be equivalent to train and hotel problems. Train and hotel problems are an abstraction of a class of identical or equivalent problems, a type of cross-system reservation protocol. Under this agreement, the user needs to be able to book both the ticket and the hotel, and the single success of either party is not the result desired by the user, so the booking of the ticket and the booking of the hotel is an atomic pair. The block chain system can be regarded as a black box with a password protocol through simple attribute abstraction, has no great difference with a train and hotel reservation system, and can be introduced into a block chain network as an additional function by researching train and hotel problems through theory and formally proving atomicity and activity of a cross-system reservation protocol, so that the problem of interconnection and intercommunication of the block chain is solved. The cross-system reservation protocol for train and hotel problems, in the context of blockchains, translates into a generic cross-chain communication protocol problem. When transactions are sent concurrently to different blockchain systems, the dependencies on the transactions translate into dependencies between blockchains. The credential that transaction T1 completed on blockchain A becomes a condition for transaction T2 to be appended on blockchain B. Completion of a transaction in blockchain B depends on completion of a transaction in blockchain a.

Blockchains that support intelligent contracts can typically be conceptualized as state machines. The cross-chain intelligent contract abstraction can be consistent with the abstraction of the blockchain, and the cross-chain intelligent contract is abstracted into state transition spanning different blockchain systems. Therefore, the cross-chain intelligent contract can be abstracted into a general state model, and the general state model uniformly processes heterogeneous block chain state machines by realizing a virtual layer. The common state model satisfies extensibility and independence. The objects and states within the general state machine are extensible. The generic state model is independent of the technology stack selection and its configuration of the underlying layer block chain. The cross-chain intelligent contract application may specify expected operations on entities contained by the general state machine and the relative order between those operations. Using a formal language, the generic state model can be represented as entity set, operation set, dependency set triplets. Entities are abstractions of objects in a blockchain system, operations are operations that these entities can support, and dependencies are constraint relationships between operations in execution order. Entities have types and attributes that, in a particular application, may characterize a particular instance of an account, contract, address, asset, etc. A prerequisite for the generic state machine conceptual model is that the generic state machine has a priori knowledge of the entities and states of each individual blockchain state machine. The operations under the common state machine are computation steps of different entity objects, and one operation is finally converted into one or more transactions in different blockchain systems. Under different blockchain systems, the transaction states processed by the consensus algorithm are not necessarily synchronized in time, which causes a problem of data inconsistency, and therefore, a constraint dependency needs to be established between operations. To ensure data consistency, at least two constraint dependencies are required: first, precondition constraint; the second is a timeout conditional constraint. A preconditioned constraint is an operation with a preconditioned constraint and can only be executed if all of its pre-dependent transactions are completed; the timeout condition constraint is that an operation, in the case where its dependencies are all satisfied, must complete within a specified time interval, giving a successful return of execution or a timeout error result.

The causal effect graph model and the generalized state machine model provide a theoretical concept model from the perspective of a formal language through defining and qualitatively analyzing the interconnection problem of a block chain system, can carry out reasoning of propositions and theorems under a mathematical logic system of the formal language, and can carry out formal testing on the specific capability of the model.

The conceptual model of block chain interconnection and interworking theory relates to the constitution of different protocols, and each protocol has its security attribute. The safety model of the conceptual model of the block chain interconnection theory is determined by the safety combination of the formed protocol cluster, and the safety model involves two problems: one is the security issue of the protocol; and secondly, the problem of whether the original respective safe protocols can ensure the safety of the combined protocol after combination. UC Security (universal Composable Security) is an important tool to solve the problem of protocol combination. As a method for proving security, a whole set of security models is defined in the UC framework to prove the security of the combined protocol in a complex environment. The UC security adopts a modularized idea, and is proved to be a UC security protocol in a UC framework, and when the UC security protocol is used as a module in a complex network environment and is combined with other protocols, the security of the combined protocol is not damaged, namely, a plurality of protocols respectively proved to be UC security in the UC framework are still secure after combination. And (4) combining a UC safety framework, carrying out mechanism deep analysis such as abnormity, errors and treatment on safety factors of the block chain system interconnection conceptual model, and designing and proving that the block chain system interconnection conceptual safety model meets the UC safety.

Cross-chain distributed application compilation techniques: the intelligent contract enables the blockchain system to expand the capability boundary of the blockchain system into a general computing platform rather than being just a transaction system for digital currency. The blockchain system plays the role of the operating system in the blockchain world, allowing blockchain applications to be created on top of its underlying protocols. In the realization of the existing block chain interconnection and interconnection technology, the problems of cross-chain protocols and the like between block chain systems, transaction consistency verification and the like are mainly solved, and a development interface for block chain interconnection and interconnection is provided. When the block chain network needs to be accessed to the interconnected and intercommunicated network, the service logic code of the corresponding inter-chain protocol and the code applied by the specific intelligent contract need to be developed, which is not friendly to developers, the development process is more complicated, and the access cost is higher. Most blockchain systems adopt different intelligent contract programming models and different programming languages, for example, the etherhouse blockchain uses a solid programming language, and the superhedger Fabric supports multiple programming languages such as Go, Java, and Node. In addition to differences in programming models and programming languages, intelligent contract cross-chain applications are challenged to extend from swap operations in the digital asset profession domain to a more general, larger application scope, supporting general-purpose operations. Therefore, the intelligent contract intermediate representation language is researched, front-end implementation of language compiling is provided for different languages, type mapping systems and conversion programs of the different languages are established through a unified programming model, and therefore developers can use the familiar languages to achieve cross-chain access research and development work. The LLVM framework and the ANTLR language recognizer technology can be used for providing a uniform compiling back-end processing program and process, providing front-end compiling service for a common intelligent contract language and converting the common intelligent contract language into an intermediate language. During the conversion process of the intermediate language, static analysis and type checking can be performed, avoiding flaws and errors in the execution of the cross-chain application.

Designing and realizing a block chain interconnection and interworking protocol: the cross-chain interconnection system mainly comprises four components: the architecture diagram of the client program, the transaction execution system, the network state blockchain system, and the transaction assurance system can be schematically shown in fig. 4.

The client program is a gateway of the cross-chain interconnection and intercommunication system and bears the interaction between the distributed application and the cross-chain interconnection and intercommunication system. The distributed application client adopts a lightweight design, and is convenient for mobile application and webpage application to access and interact with an interconnection and interworking system. The transaction execution program serves as a driver of the bottom layer blockchain, application codes provided by a client are compiled into a program, and the program is run and converted into transactions which can be executed in the blockchain system. Both the client and the transaction execution system adopt an inter-chain interoperation protocol to ensure the safe execution of the transaction in different blockchain systems. The inter-chain interoperability protocol consists of two parts: a transaction state storage layer and a transaction guarantee intelligent contract. The transaction state storage layer is born by a network state block chain system, and the network state block chain is a block chain in the block chain and provides an objective unified view for the execution state of the distributed application. The transaction guarantee function contract is responsible for monitoring the execution state and structure of the transaction and providing arbitration service for the transaction. Under the condition of abnormity, the transaction security intelligent contract cancels all executed transactions, and returns the transaction amount to the account of the original participant to ensure the atomicity of the transaction.

In order to ensure the correct execution of the distributed application, all transactions in the executable program of the distributed application need to be submitted to the corresponding block chain for execution, and the precondition and time-limited condition of the transaction must be satisfied. The execution process of the cross-chain distributed application is simple in abstraction on a model, but faces huge challenges in the actual execution process. Because in an untrusted environment there is no trusted central authority to coordinate the sequential execution of transactions on different blockchains and trust between the client and the transaction execution system cannot be guaranteed. To ensure proper execution of the cross-chain distributed application, a cryptographic protocol is added between the client and the transaction execution system, thereby securing execution of the executable program on different blockchains. The inter-chain interoperability protocol accomplishes the tasks specified by the cryptographic protocol by both systems. The network state data layer is acted by a blockchain system and is responsible for recording the execution result of the cross-chain distributed application and providing a real and objective consistent query view. The network state database organizes the final transactions of different blockchain systems into a Mercker tree, so that the final state of the transaction state is uniformly described, and verifiable evidence is provided. Meanwhile, the state blockchain system also provides verifiable records for the operation behaviors of the client and the transaction execution in the cross-chain transaction execution, which are respectively executed, and the function is realized by a behavior consensus algorithm.

The transaction assurance intelligence contract is a code arbitrator that submits a transaction state verifiable proof from the network state blockchain as input to determine the final execution result of the distributed application and utilizes the record of operational behavior to decide responsibility for a transaction failure.

The cross-chain interconnection method of the block chain in the embodiment of the invention solves the following technical problems:

the commonality problem of block chain interconnection: intelligent contracts executed in blockchains and blockchain networks may be viewed as state machine models. Distributed applications across chains can also be abstracted into state machines, maintaining consistency across conceptual models. To achieve this, a unified state model is introduced. The unified state model defines and describes the cross-chain distributed application uniformly, is a chain-independent and extensible model and is used for describing state transition between different blockchain systems. The unified state model uses a virtual layer to uniformly solve the problem of heterogeneity of the underlying zone blockchain network. This isomerism is achieved in two ways: the first aspect is the difference in internal structure of the blockchain system itself, such as consensus systems, data structures, etc.; the second aspect is the variability of the intelligent contract execution environment and the programming language. To overcome these two differences, different blockchains are uniformly abstracted into objects with common state variables and functions, and the cross-chain distributed application abstracts the desired operations on these objects and the relative execution order of these operations.

In a formal language, a unified state model may be defined as M ═ E, P, C, where E is the set of operable entities on the blockchain, P is the set of operations that can be performed on the entities, and C is the set of these operation dependent constraints. An entity is an abstraction of a blockchain object and can be used to describe an object defined in a blockchain. The entities have types, each type having different attributes, such as account entities and address entities, etc. The operations in the unified state model are computation steps performed on different pairs of entities, which may belong to the same blockchain or to different blockchains. Each operation is eventually compiled into one or more transactions in different blockchain systems. Considering the asynchrony of the blockchain transaction execution structure, the unified state model sets up two types for dependencies between operations: a precondition and a timeout condition.

In order to meet the universality of interconnection and intercommunication among heterogeneous multi-chains, an inter-chain interoperation protocol is designed based on a general state model. The inter-chain interoperability protocol includes four base protocols and two phases. The four basic protocols are respectively a protocol realized by a client, a protocol realized by a transaction execution system, a protocol realized by a network state system and a protocol realized by a transaction guarantee intelligent contract. The two phases are a program execution phase and a insurance compensation phase. During the program execution phase, all transactions in the executable program need to be submitted into the corresponding blockchain system. During the insurance compensation phase, the correctness and mistakes of the program execution are arbitrated.

Client protocol and runtime transaction state: during the execution process of the transaction, the effective state of the transaction is a state set, the value of the latter state is the high-level state of the former state, and the transaction states change sequentially during the execution process of the transaction. For each state, the inter-chain interoperability protocol provides a proof of argumentation. When the execution phase ends, the final execution state of the cross-chain distributed application is determined by the state of all transactions.

The exchange protocol between the client program and the transaction execution system is completed through the link state channel. In order to clarify the liability assertions of errors in the transaction process, each party's execution steps are recorded, allowing clients and verifiable programs to pledge their execution steps.

Network state blockchain architecture: the network state storage layer adopts a block chain system to act, and the main purpose is to provide an objective view for the execution situation of the cross-chain distributed application. The network state storage layer selects the blockchain as a design rather than a general database, mainly because of technical characteristics of traceability, non-repudiation, fault tolerance and the like of the blockchain system. Blocks of the network state block chain contain necessary fields, the blocks are connected in series by using hash fields, and the Merckel tree is used for storing transactions and states. In order to support other functions of the network state blockchain, two additional merkel tree roots are included in the blockdata structure of the network state blockchain: a state root and an operation root.

The state root is the root of the Mercker tree for the transaction state in the blockchain network. The network state blockchain represents the transaction state of a blockchain using the transaction root and the state root of the blockchain. The transaction root and the state root in one blockchain represent the mercker tree root of a transaction and the mercker tree root of a stored state, respectively. The network state blockchain only stores blockchain states related to the cross-chain distributed application, but not all states of the whole chain, and the basis for judging whether blocks are related is whether the blocks in the blockchain pack transactions in the cross-chain distributed executable program.

The operation root stores the Merck tree root of a leaf node formed by certificates submitted by the client and the transaction execution system when the operation is executed. Each certificate represents an operational step performed by a client program or transaction execution system during execution of a cross-chain distributed application executable. For purposes of verifying operational behavior, transaction participants can construct a Mercker tree to prove the mapping of operational behavior to certificates and their association to tiles in a network state blockchain. In the event of an error or abnormality in the transaction, these operations prove to provide a basis for the transaction execution assurance program to determine the responsible party for the failure of the transaction.

The transaction execution system executes the protocol: after the cross-chain distributed application dependency graph is generated, the transaction execution system initiates an execution session. The primary task of initialization is to create and deploy a transaction execution assurance intelligence contract to protect the execution of transactions. In order to complete the task, the transaction execution system firstly sends a request to the cross-chain transaction security system, creates a transaction execution security intelligent contract for the transaction dependency graph, and then deploys the transaction execution security intelligent contract into the network state block chain after agreeing by the client. In the process of agreement and the process of next transaction execution, the transaction participants use their digital signatures to sign the operated objects and then generate certificates, and the certificates are stored in a network state block chain together with the transactions.

In order for the cross-chain transaction assurance system to roll back submitted transactions in the event of an erroneous execution result, the client program and the transaction execution program need to pay sufficient funds to the transaction assurance program. As for the amount of the pledge funds, the simplest method is the total amount of the transaction, and if a more reasonable and fair proportion is calculated, a proportion calculation and calculation algorithm needs to be designed to optimize the step.

After the cross-chain transaction security intelligent contract is instantiated, the transaction execution system initializes a session daemon process and advances the transaction flow by using different processing functions. The transaction invocation is triggered when the transaction care service of the transaction execution system recognizes that the preconditions for the transaction have been fulfilled. In the execution process of the transaction, the client program and the transaction execution system need to identify the execution state of the transaction in sequence, and then construct the transaction on the target chain based on the transaction data of the logic, and further submit the transaction to the corresponding target chain. The transaction assurance system will check continuously whether the submitted transaction is completed within a defined time, and then adjudicate the status of the transaction.

The execution of cross-chain transactions depends on the state of the blockchain network and the state of the transaction state blockchain system. There are two care-of-processes inside the transaction execution program to read the state of these block chains. The first care-of process monitors the target chain and queries the status of the submitted transaction by reading the target chain ledger. If the submitted transaction is eventually validated on the target chain, the transaction execution system may notify the client of the completion of the transaction. In addition to reading the transaction state on the target chain, the transaction execution program needs to extract the mercker's proof in the transaction state block chain to verify the finality of the transaction execution, which is the second care process.

Transaction execution support system protocol: and the transaction execution guarantee system generates a transaction execution arbitration code according to the transaction dependency tree, and the transaction execution arbitration code is deployed into the transaction state block chain in the form of an intelligent contract. The internal logic of the smart contract may use the transaction state as a parameter to track the state of each transaction in the transaction dependency graph. The transaction execution system may invoke the transaction execution assurance system to execute the contract at regular intervals. When transaction execution is wrong or overtime, the intelligent dating execution contract combines the terms of the date execution contract to carry out backspace and punishment of the transaction.

Programmability issues for cross-chain distributed applications: the programmability problem of cross-chain distributed applications can be solved by a programming framework. The design of the programming framework mainly focuses on the functions of the compiler, and the work of the compiler is divided into front-end functions and back-end functions. Front-end functions include common variables and methods for extracting entities, operations and dependencies from cross-chain applications and intelligent contracts from blockchain networks. Designing a unified type system can meet the requirements of two aspects: abstracting intelligent contracts written in different programming languages into an interoperation entity in a unified way; cross-chain applications programmed using different languages may be converted to a unified programming language. The compiler performs semantic checks on all entities, operations, and dependencies to ensure correctness and security of the distributed cross-chain program, and finally compiles the program into an executable program. The organizational structure of the executable program is a transaction dependency graph.

And the universal compiling tool is used for constructing a unified type system. By using the unified type system, a developer does not need to consider the specific data structure and the intelligent contract programming language of the underlying blockchain when writing the cross-chain distributed application, which is equivalent to providing a virtual layer for different underlying blockchain systems, and then speaking the unified type to convert the type supported by the specific blockchain in the dynamic execution process of the program. The design of the unified system achieves the purpose of uniformly describing and writing different language types and operations of different block chains.

The basic building blocks of a programming language are consistent with a unified state model, allowing developers to directly specify entity objects of operations, operations to be performed, operation dependencies in a cross-chain distributed application. In a cross-chain distributed application, an entity, an operation and a dependency condition need to be defined. In the process of compiling the cross-chain distributed program by the compiler, semantic check is carried out on the correctness and the safety of the cross-chain distributed application, and the matching of types and the validity of verification parameters are checked. Besides checking, the dependence is also verified, and the dependence of all the operations is verified to meet the directed acyclic graph data model, so that the conflict between the constraint conditions is avoided.

After all verifications of the cross-chain distributed application, the compiler will produce an executable program. The logical structure of the executable program is a transaction dependency graph, the nodes of the graph are transactions, and the edges of the graph describe the dependencies between transactions. The transaction represented by a node includes all the information of which transaction is performed on which blockchain and the metadata of the transaction.

Block chain interconnection security issues: the safety problem of the interconnection and interworking of the block chains is essentially the correctness and safety problem of the inter-chain interoperation protocol. The inter-chain interoperability protocol may represent its cryptographic protocol abstraction with ideal functionality. Given the existence of trusted entities, the ideal functionality clarifies the correctness and security attributes that a cross-chain interoperation system wishes to implement. The ideal function describes the function of the inter-chain interoperation protocol and the interface definition thereof, and comprises three aspects of transaction session, transaction state update, rollback contract execution and the like. In a transaction session, a client and a transaction execution service request chain interoperability protocol securely execute a cross-chain distributed application. The inter-chain interoperation protocol gives the cross-chain distributed application to the description in the form of a transaction dependency graph, and provides a guarantee intelligent contract for the correctness of transaction execution. As a trusted entity, the inter-chain interoperability protocol assigns each transaction participant a private key so that they can sign the transaction, computing a certificate. Each participant needs to mortgage sufficient funds against the inter-chain interoperability protocol. The inter-chain interoperability protocol defines a series of interfaces to receive calls from external systems to complete the update of the transaction state. Within each interface, the inter-chain interoperability protocol performs the necessary correctness checks to ensure that the transition to the transaction state is legitimate. In all interfaces, the inter-chain interoperability protocol computes a proof for the corresponding transaction state, sends the proof to the transaction participants, and informs the inter-chain interoperability protocol of the actions taken and performed. When the timeout occurs, the transaction participants can call the interface for ending the transaction to trigger the execution of the transaction security intelligent contract code. Based on the final state of each transaction, the transaction arbitration intelligent contract executes transaction arbitration procedures according to the transaction state decision tree, judges and divides the responsibility of transaction failure, and then performs rollback and punishment on the transaction.

Under trusted assumptions, it is not difficult to infer that the inter-chain interoperability protocol provides the following correctness and security. First, after a specified time limit has been exceeded, execution of the transaction either ends properly or fails. Both the preconditions and the execution time limit constraints are satisfied when properly finished. When the execution fails, the inverse operation of the transaction is executed to restore the original state. Second, the inter-chain interoperability protocol will identify the responsible party that caused the transaction to fail, giving the necessary penalty.

By the embodiment of the invention, the method can be applied to the following application scenes, wherein the application scenes comprise but are not limited to:

and (4) asset transplantation: asset transfer may allow a user to transfer its assets from one blockchain to another blockchain. The transfer between blockchains is bidirectional and assets can be transferred from further blockchains to the current blockchain at any time.

Atom exchange: atomic exchange allows two parties to trade each other, exchanging different digital assets, at different blockchains. The parties involved in the transaction need to have an account or address on each different blockchain. Transactions occur simultaneously in all blockchains. Atomic exchange needs to ensure that asset transfers of both parties either happen or fail at the same time. Atomic exchange is also a common transaction mechanism for decentralized transactions.

The cross-chain prediction machine comprises: the predictive engine provides external data to the blockchain system. The external data provided by the cross-chain prediction machine can come from another blockchain. For example, the cross-chain prediction machine extracts the relevant information of the transaction from the external blockchain, and then triggers the action of the intelligent contract on the local blockchain system to execute the relevant operation.

Asset retention: asset retention is the ability to lock assets onto a blockchain. The locked asset is then unlocked when certain conditions are met on the other blockchain. For example, the asset retention function may be used in a business that pays security margins.

Cross-chain intelligent contracts: the cross-chain intelligent contract can seamlessly realize various dependencies of the blockchain on other blockchains, so that the dependency and cooperation of various situations are realized. For example, an intelligent contract to pay a bonus on one blockchain may require checking that the current user is a registered equity holder on the other chain at about the time of payment of the bonus. Of course, the cross-chain intelligent contract has more usage scenarios.

According to the cross-chain interconnection method of the block chains, the cross-chain interconnection between the block chains can be conveniently, safely and reliably realized, and particularly, when the heterogeneous block chains are subjected to interconnection, the transformation of the block chains can be effectively reduced, so that the cost of cross-chain operation is reduced.

Further, as shown in fig. 5, an embodiment of the present invention discloses a block chain cross-chain interconnection system, including: a determination module 510, a protocol design module 520, an application creation module 530, and an optimization module 540.

The determining module 510 is configured to determine a block chain interconnection theoretical model according to a block chain and a cross-chain requirement of the block chain. The protocol design module 520 is configured to obtain an inter-chain interoperation protocol for interconnection and interworking of the block chains based on the theoretical model for interconnection and interworking of the block chains. The application creation module 530 is configured to create a cross-chain distributed application according to a preset rule. The optimization module 540 is configured to perform a cross-chain operation between two preset block chains through the cross-chain distributed application, so as to perform function verification and protocol evaluation on the block chain interconnection and interworking theoretical model, and implement optimization on the block chain interconnection and interworking theoretical model.

According to the cross-chain interconnection system of the block chains, the cross-chain interconnection between the block chains can be conveniently, safely and reliably realized, and particularly, when the heterogeneous block chains are subjected to interconnection, the transformation of the block chains can be effectively reduced, so that the cost of cross-chain operation is reduced.

It should be noted that a specific implementation manner of the inter-chain interconnection system of the block chain in the embodiment of the present invention is similar to a specific implementation manner of the inter-chain interconnection method of the block chain in the embodiment of the present invention, and please refer to the description of the method part specifically, which is not described herein again.

Based on the same inventive concept, another embodiment of the present invention provides a non-transitory computer-readable storage medium, on which a computer program is stored, where the computer program, when executed by a processor, implements all the steps of the above block chain cross-chain interconnection method, for example, determining a block chain interconnection and intercommunication theoretical model according to cross-chain requirements of a block chain and a block chain; based on the block chain interconnection theoretical model, obtaining an inter-chain interoperation protocol of block chain interconnection; creating a cross-chain distributed application according to a preset rule; and performing chain-crossing operation between two preset block chains through the chain-crossing distributed application to perform function verification and protocol evaluation on the block chain interconnection and intercommunication theoretical model, so as to realize optimization of the block chain interconnection and intercommunication theoretical model.

The above-described embodiments of the apparatus are merely illustrative, and the units described as separate parts may or may not be physically separate, and parts displayed as units may or may not be physical units, may be located in one place, or may be distributed on a plurality of network units. Some or all of the modules may be selected according to actual needs to achieve the purpose of the solution of the embodiment of the present invention. One of ordinary skill in the art can understand and implement it without inventive effort.

Claims

1. A method for interconnecting a block chain across chains is characterized by comprising the following steps:

creating a cross-chain distributed application according to a preset rule;

2. The method according to claim 1, wherein determining the theoretical model of interconnection and interworking of blockchains according to the cross-chain requirements of blockchains and blockchains comprises:

and analyzing the block chains and the cross-chain requirements of the block chains to abstract out the block chain interconnection theoretical model.

3. The method according to claim 1, wherein obtaining inter-chain interoperation protocol for interconnection and interworking of block chains based on the theoretical model for interconnection and interworking of block chains comprises:

and taking the block chain interconnection and intercommunication theoretical model as a guide to obtain inter-chain interoperation protocols and related mechanisms of block chain interconnection and intercommunication, wherein the related mechanisms comprise a cross-chain transaction verification mechanism, a cross-chain safety management mechanism and a uniform programming language of a cross-chain intelligent contract.

4. The method according to claim 3, wherein the safety of the block chain interconnection theory model satisfies the safety of the UC safety framework.

5. The method for interconnecting blocks according to claim 1, wherein the creating a cross-chain distributed application according to a preset rule comprises:

the cross-chain distributed application is developed using a unified state model and a unified programming language.

6. The method according to claim 1, wherein the inter-chain interoperation protocol for interconnecting and interworking block chains comprises four sub-protocols and two phases, wherein the four sub-protocols comprise a client-implemented protocol, a transaction execution system implemented protocol, a network state system implemented protocol, and a transaction assurance intelligence contract implemented protocol, and the two phases are a program execution phase and an insurance pursuit phase, respectively, wherein in the program execution phase, a transaction in an executable program needs to be submitted to the corresponding block chain, and in the insurance pursuit phase, the correctness of program execution is arbitrated.

7. The method of claim 6, further comprising:

and encrypting between the client and the transaction execution system according to a preset password protocol.

8. A block chain inter-link system, comprising:

9. A non-transitory computer readable storage medium having stored thereon a computer program, wherein the computer program, when executed by a processor, implements a cross-chain interconnection method of a blockchain according to any one of claims 1 to 7.