CN111666323B - Cross-chain intercommunication method and system for block chain - Google Patents

Abstract

The invention provides a cross-chain interconnection method and a system of a block chain. The cross-chain interconnection method of the block chain comprises the following steps: determining a blockchain interconnection theoretical model according to blockchain and a blockchain crossing demand; obtaining inter-chain interoperation protocols of block chain interconnection based on the block chain interconnection theoretical model; creating a cross-chain distributed application according to a preset rule; and performing cross-chain operation between two preset blockchains through the cross-chain distributed application so as to perform function verification and protocol evaluation on the blockchain interconnection theoretical model, thereby realizing optimization of the blockchain interconnection theoretical model. The cross-chain interconnection method of the blockchains can conveniently, safely and reliably realize cross-chain interconnection among the blockchains, and particularly when the interconnection among heterogeneous blockchains is performed, the transformation of the blockchains can be effectively reduced, so that the cost of cross-chain operation is reduced.

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 system of a block chain.

Background

From the development process of the blockchain, the interconnection and interworking between the blockchain systems become the first problem for restricting the development of the blockchain technology. Because the head blockchain system does not exhibit a chain's ability to dominate all, applicable scenarios, a blockchain multi-chain closed concurrent pattern is developed. At present, the block chain crossing technical scheme is mainly divided into: notary mechanism, side chain, relay, hash lock, distributed private key control, atomic exchange protocol, bridging technology, in-chain, etc.

However, there is no widely accepted cross-chain mechanism at present, and technical difficulties of interconnection and interworking of blockchain systems include cross-chain transaction verification problem, cross-chain transaction management problem, locking asset management problem, multi-chain protocol adaptation problem, cross-chain security guarantee problem, and the like. Thus, cross-chain interconnection is restricted.

Disclosure of Invention

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

In a first aspect, the present invention provides a method for inter-link interworking of blockchains, including:

Determining a blockchain interconnection theoretical model according to blockchain and a blockchain crossing demand;

obtaining inter-chain interoperation protocols of block chain interconnection based on the block chain interconnection theoretical model;

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

and performing cross-chain operation between two preset blockchains through the cross-chain distributed application so as to perform function verification and protocol evaluation on the blockchain interconnection theoretical model, thereby realizing optimization of the blockchain interconnection theoretical model.

In a second aspect, the present invention provides a blockchain cross-chain interconnect system, comprising:

the determining module is used for determining a blockchain interconnection theoretical model according to the blockchain and the blockchain crossing requirements;

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

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

and the optimization module is used for performing cross-chain operation between two preset blockchains through the cross-chain distributed application so as to perform function verification and protocol evaluation on the blockchain interconnection theoretical model and realize optimization on the blockchain interconnection 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 a blockchain cross-chain interconnection method according to the first aspect described above.

The above 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, the inter-chain interconnection between the blockchains can be conveniently, safely and reliably realized, and especially when the inter-interconnection between heterogeneous blockchains is performed, the transformation of the blockchains can be effectively reduced, so that the cost of the inter-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 invention or the technical solutions of the prior art, the drawings that are necessary for the description of the embodiments or the prior art will be briefly described, it being obvious that the drawings in the following description are only some embodiments of the invention and that other drawings can be obtained from these drawings without inventive effort for a person skilled in the art.

FIG. 1 is a flow chart of a method for cross-chain interconnection of blockchains provided in an embodiment of the invention;

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

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

FIG. 4 is a schematic block chain interconnection protocol frame diagram of a cross-chain interconnection method of block chains according to an embodiment of the present invention;

FIG. 5 is a block diagram of a block chain cross-link interconnect system in accordance with one embodiment of the present invention.

Detailed Description

The following describes the embodiments of the present invention further with reference to the accompanying drawings. The following examples are only for more clearly illustrating the technical aspects of the present invention, and are not intended to limit the scope of the present invention.

The following describes a cross-chain interconnection method and system of blockchains according to an embodiment of the present invention with reference to the accompanying drawings.

Before describing a cross-link interconnection method of de-cross-links according to an embodiment of the present invention, a description is first given of a current cross-link problem.

The cross-chain technology is a main mode for solving the problem of interconnection and interworking of block chain systems. Cross-link technology is interconnected with blockchain systems, like TCP/IP is interconnected with the Internet. The cross-chain technique is a technique that allows a value to directly circulate across a chain and a barrier between chains. The cross-chain interactions can be divided into isomorphic and heterogeneous chain cross-links according to the differences in the underlying technology platforms of the blockchain being spanned. The security mechanism, the consensus algorithm, the network off-slope and the block generation verification logic among isomorphic chains are the same, and the inter-chain interaction among the isomorphic chains is relatively simple; the cross-chain interaction of heterogeneous chains is relatively complex, the composition form and the deterministic guarantee mechanism of the blocks are quite different, and the direct cross-chain interaction mechanism is not easy to design.

The current block chain crossing technical scheme is mainly divided into: notary mechanism, side chain, relay, hash lock, distributed private key control, atomic exchange protocol, bridging technology, in-chain, etc.

However, there is no generally accepted cross-chain mechanism, and the technical difficulties of the blockchain system (i.e. blockchain) interconnection and interworking include the following five aspects:

cross-chain transaction validation problem:

interconnection and interworking between blockchains are achieved, and trust mechanisms between blockchain systems are designed primarily so that one blockchain can receive and verify transactions on another blockchain. Confirmation and verification of transactions involves two problems, one is to confirm that the transaction has occurred and to write into the blockchain ledger; and secondly, verifying that the transaction has been confirmed by enough nodes in the system. Currently common cross-chain transaction verification mechanisms are notary mechanism and 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 header+SPV mode stores the block header data of the external blockchain system provided by the notary in the network of the notary and verifies the transaction according to the SPV mechanism.

Cross-chain transaction management problem:

a complete cross-chain transaction can split a plurality of sub-transactions, each sub-transaction is processed in a block chain system to which the sub-transaction belongs, and the sub-transactions form a transaction, so that cross-chain transaction management is needed to ensure the consistency and atomicity of the transaction. Cross-chain transaction management is in turn divided into two sub-problems, namely the final deterministic problem of transactions and the atomicity problem of transactions. In cross-chain transaction management, to guarantee the final certainty of a transaction, there are typically three schemes: wait for a sufficient number of acknowledgements, block entanglement, and use of a consensus algorithm such as DPoS or BFT. Waiting for a sufficient number of acknowledgements is the simplest and cruder method, which has the disadvantage that the transaction time becomes long. The principle of block entanglement is to have the blocks of two chains have a dependency relationship, and when a block on one chain is revoked, the related blocks on the other chain are automatically revoked. Compared with the PoW consensus algorithm, the final certainty is more easily achieved by the consensus algorithm such as DPoS or BFT, and the blockchain system using the consensus algorithm can realize the cross-chain transaction efficiently. Atomicity of transactions is a fundamental requirement for implementing cross-chain transactions, and is also a difficulty that must be addressed by cross-chain transactions.

Locked asset management problem:

bi-directional anchoring is the process of bi-directional transfer of assets on the backbone and side chains in a 1:1 redemption ratio. A key issue in the bi-directional anchoring design is how to ensure that the locked asset is safely released without causing double spending problems by who manages the locked account and performs locking and unlocking operations. In addition, it is equally important how to ensure that the total amount of assets for both chains does not change. Regarding the management of asset locking, there are currently a single escrow pattern, a federation escrow pattern, and an intelligent contract pattern. The single escrow pattern is an asset that is responsible for managing locks by a single escrow, performing and supervising unlocking operations of the locked asset. The single-custodian mode, while simple and easy to implement, is too dependent on a centralized custodian. The more decentralised mode is a federation hosting mode in which N notary persons in the federation all trade and vote independently when receiving an unlock request across chains, and when the number of votes reaches a threshold M, the locked asset can be handled. The intelligent contract mode is to further de-centralize, and the precondition of this scheme is that the blockchain system is capable of supporting intelligent contracts and storing the blockhead of the external blockchain to verify external transaction data.

Multi-chain protocol adaptation problem:

with the development and the continuous landing of the application of the blockchain technology, the blockchain ecological system in the future is necessarily an ecological system with multiple chains coexisting and interconnected. The multi-chain interconnection implies two layers of meanings, namely how the existing blockchains realize interconnection; secondly, how to prepare the block chain to be developed for interconnection. 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, and mainly aims at the existing blockchain system, different blockchain application systems at the upper layer are adopted, and the development of a bottom layer cross-chain mechanism is performed. Existing blockchain systems are typically heterogeneous chains that require one-to-one interfacing. The passive compatible scheme is designed from bottom to top, mainly aims at a block chain system which is not yet developed, firstly builds a bottom layer cross-chain platform, and then develops a new block chain system based on the cross-chain platform, or simply, conveniently and safely accesses the existing block chain system into the platform, and the system sharing the cross-chain platform is convenient.

Cross-chain safety guarantee problem:

when two systems interact, they will not affect each other, if inter-link security cannot be isolated, then if one link is under attack, the entire cross-link network will be affected. How to guarantee the security of the own system and the counterpart system in the cross-chain transaction process is a considerable problem. In general, the following three aspects can be considered: moderately isolating, detecting security events and guaranteeing the correctness of the cross-chain transaction. The links should keep their independence, and cross-link transactions should be processed by a third party node or an independent module as much as possible, so that when a problem occurs in the cross-link transactions, the processing of the transactions of the links themselves is not affected. If the third party node or the independent module has the capability of detecting the security event and the response capability, the system architecture isolation is further based on the system architecture isolation, so that the cross-chain protocol or the system has the function similar to a firewall.

Fig. 1 shows a flowchart of a cross-chain interconnection method of a blockchain according to an embodiment of the present invention, and as shown in fig. 1, the cross-chain interconnection method of a blockchain according to an embodiment of the present invention includes the following steps:

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

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

Specifically, a blockchain interconnection theoretical model is used as a guide to obtain an inter-chain interoperation protocol and a related mechanism of blockchain interconnection, wherein the related mechanism comprises a cross-chain transaction verification mechanism, a cross-chain security management mechanism and a unified 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 one embodiment of the invention, the inter-chain interoperation protocol of the blockchain interconnection includes four sub-protocols and two phases, wherein 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 assurance smart contract, and the two phases are a program execution phase and a insurance compensation phase respectively, wherein in the program execution phase, a transaction in an executable program needs to be submitted to a corresponding blockchain. During the guard compensation stage, the accuracy of program execution is arbitrated.

In addition, encryption can be performed between the client and the transaction execution system according to a preset cryptographic 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: performing cross-chain operation between two preset blockchains through cross-chain distributed application so as to perform function verification and protocol evaluation on the blockchain interconnection theoretical model, and optimizing the blockchain interconnection theoretical model. Therefore, the optimized block chain interconnection theoretical model can be used as a reference for realizing the cross-chain interconnection of the block chains by using the universal reference conceptual model and the key technology prototype, and further, the cross-chain interconnection of the block chains can be realized simply and conveniently by using the universal reference conceptual model and the key technology prototype.

Through the steps S101 to S104, the actual state of the block chain technology development can be closely related, the general interconnection and intercommunication technology of various block chains is concerned, key problems such as cross-chain transaction verification, cross-chain transaction management, cross-chain multi-protocol adaptation, cross-chain safety guarantee and the like in the interconnection and intercommunication of block chain systems are considered, and from the aspects of theoretical model abstraction and software engineering realization, the block chain system interconnection and intercommunication theoretical model (namely, the block chain interconnection and intercommunication theoretical model) and the block chain interconnection and intercommunication prototype system (namely, the cross-chain distributed application) are researched. And by constructing a blockchain testing environment taking tendermine as an engine and a testing environment of a alliance chain Hyperledger Fabric blockchain in a specific example, performing cross-chain operation of a prototype system and the two chains, and performing blockchain interconnection and interworking model function verification and protocol evaluation, a general reference conceptual model for solving the key problem of blockchain interconnection and interworking and key technology prototype implementation are provided.

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

(1) The programming framework and the matched tool set are provided, so that the development of the cross-chain distributed application is facilitated. By abstraction, a virtual layer is provided over different underlying heterogeneous blockchains to mask the underlying blockchains' heterogeneity and complexity, and a unified state model and programming language is utilized to describe and develop 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, and is a universal cross-chain protocol, and the application range of the protocol not only covers the exchange of digital assets, but also can support generalized data exchange. The inter-chain interoperation protocol can implement complex cross-chain operations involving intelligent contract calls on different blockchain networks and ensures the security of complex cross-chain calls. The ideal functionality is used to represent the security attributes of the inter-chain interoperability protocol, which is demonstrated using the UC security framework.

(3) A system prototype was developed that uses two different cross-chain distributed applications to verify and evaluate the prototype system.

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

In theoretical analysis, according to basic theories such as a state machine, language compiling, a safety framework and the like, the problem of interconnection and intercommunication of the blockchain is abstracted into a general conceptual model, 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 into the interconnection problem under the Internet architecture, and the interconnection models of different block chain networks are built by using connectors, routers and bridges. Existing abstract models are cross-chain asset transfer models implemented based on payment channels and payment channel networks. And the block chains are regarded as mutually independent state machine networks based on a general model of the state machines, and the interconnection and the interworking are realized by the distributed state machines to provide execution of intelligent contracts and realize state transition on different block chains. Theoretically, whether an atomic exchange protocol or a cross-chain inter-chain protocol, follow a pre-transaction from one blockchain to another, or a post-transaction, or a bi-directional transaction, may be represented using a graph model.

In the research of the cross-chain technology, the existing blockchain interconnection research documents are researched and carded, the common attributes of the problems researched by the research documents are summarized, and the research thought, the research method and the research result are analyzed and compared. Typical engineering projects for solving the problem of block chain interconnection and interworking are selected, and from the perspective of software engineering, the functional characteristics, system design and code implementation of the engineering projects are analyzed and summarized, and key technologies and advantages and disadvantages of the typical projects are summarized.

In prototype research and development, through re-understanding and redefining of cross-chain concepts, specific connotation of interconnection and interworking is defined, and the attribute, relationship and operation of the concepts are specified. Specific details of each protocol and module are designed based on the concept and the general model, and a programming language development system prototype is selected.

In experimental evaluation, source codes of a prototype system are compiled to become executable programs, the executable programs are deployed in a test environment, a client or a wallet system is used for sending cross-chain transactions, functional tests and performance tests are carried out on the prototype system according to different scenes and test cases, and the correctness of execution of the cross-chain transactions of a detection system is evaluated; counting system performance test indexes, and inspecting system transaction delay and performance conditions; simulating a block chain malicious attack and evaluating the security of a prototype system.

In the scenario application, the cross-chain application scenario comprises asset transfer, asset exchange, asset retention, cross-chain intelligent contracts and cross-chain predictors. The functions of the cross-chain intelligent contracts and predictors are used, and specific businesses such as the guarantee money of financial transactions, option transactions, innovation of financial derivatives and the like are combined to develop scene application exploration.

In research content, interconnection and interworking between blockchains are realized by information, data and value flowing among chains. Theoretically, the method comprises the contents of general problem abstraction, formalized language description and reasoning, formalized security attribute analysis and the like. From the engineering realization aspect, the method relates to the aspects of inter-chain communication protocol, cross-chain data exchange protocol, cross-chain transaction verification, cross-chain security management, cross-chain intelligent contract application development and the like. The project aims to abstract a general conceptual model through analysis of blockchain and cross-chain requirements thereof. Based on the guidance of the general conceptual model, modules such as a cross-chain protocol, a cross-chain transaction verification mechanism, a cross-chain security management mechanism, a cross-chain intelligent contract programming language and the like are designed, a blockchain network prototype with interoperability and programmability is constructed, and theoretical inspection and prototype evaluation are realized.

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

The block chain interconnection theory model analysis comprises the following steps: blockchain interworking is a combination of different blockchain systems, each representing a distributed data ledger, where transaction execution may span multiple blockchain systems, where data recorded in a blockchain may be retrieved and validated by another transaction, possibly from the outside, in a semantically compatible manner.

The interconnection of the blockchain is required in many different scenes, and from the perspective of high-order application, the application scene of the interconnection is expanded from finance to identity verification, and the value of the interconnection of the blockchain can be reflected in many different application scenes. From the standpoint of calculation theory, different types of interconnection scenes can be simply classified and uniformly defined as a causal effect graph model. Specifically, there are three types of models: forward cause and effect, reverse cause and effect of dependency. These three types essentially reveal causal relationships between transaction order and state changes among different blockchains. These three types do not occur simultaneously in a practical application scenario. From a logical aspect, interworking is essentially a reliable, stable causal relationship of event-induced state changes in different block chain systems.

Where forward cause and effect may describe that chain A may trigger an event on chain B to occur, equivalent to say that chain B may read chain A's data. An inverse cause and effect is that chain B can trigger an event on chain a that occurs in the opposite direction. Dependency cause and effect refers to the occurrence of an event that triggers both chain A and chain B simultaneously by a change in state of chain C, which simultaneously produces a dependency on the state data of chain C.

The relay cross-chain mechanism provides two cross-chain interaction types, forward causal and reverse causal, 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 cross-chain mechanism provides execution of the dependency causal model by presentation of hash values as a common cause. With these three causal effect models, the complexity of the calculations and interpretations can be deduced from the equivalent transformations of the three causal effect models and the model combinations. The equivalent transformation of the three causal effect models is to explore the equivalent transformation among three mechanisms of relay, notary and hash locking, and provides a theoretical basis for the optimal design of the mechanisms. The combination of the three models is to solve the maximum set of the usage scenario by using the three basic models, explore a method for reducing the cross-link complexity in a complex scenario, for example, to express the matters of different aspects of the interconnection and interworking problem by adopting a high-level cross-link programming language (conditional event sending and interception mechanism), and provide theoretical guidance for the engineering realization of the cross-link.

From the point of view of mathematical logic, the forward cause and effect model may be equivalent to train and hotel problems. Train and hotel problems are abstractions of a class of identical or equivalent problems, a cross-system reservation protocol. Under this protocol, the user needs to be able to order both the ticket and the hotel, and either party is not successful as the result desired by the user, so the reservation of the ticket and the reservation of the hotel are a pair of atomic operations. The blockchain system is simple in attribute abstraction, can be seen as a black box with a password protocol, has no great difference with a train and hotel reservation system, and can be introduced into a blockchain network as an additional function to solve the problem of interconnection and intercommunication of blockchains by formally proving atomicity and activity of a cross-system reservation protocol through theoretical research on the problems of trains and hotels. The cross-system reservation protocol of train and hotel problems, in the context of blockchain, 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 completes at blockchain A is the condition for transaction T2 to append on blockchain B. Completion of the transaction in blockchain B depends on completion of the transaction in blockchain a.

Blockchains supporting smart contracts can generally be conceptualized as state machines. The cross-chain intelligence contract abstraction may be consistent with the abstraction of blockchains, abstracting the cross-chain intelligence contracts into state transitions across different blockchain systems. Thus, cross-chain intelligence contracts can be abstracted into a generic state model that handles heterogeneous blockchain state machines uniformly by implementing a virtual layer. The generic state model satisfies scalability and independence. Objects and states within a generic state machine are extensible. The generic state model is independent of the technology stack selection and configuration of the underlying blockchain. The cross-chain smart contract application may specify the expected operations on the entities contained by the generic state machine and the relative order between these operations. Using formal language, the generic state model may be represented as a set of entities, a set of operations, a set of dependencies, or a triplet of sets. 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. The entity has a type and attributes that, in a particular application, may characterize a particular instance of an account, contract, address, asset, etc. A precondition for a conceptual model of a generic state machine is that the generic state machine predicts the entities and states of each individual blockchain state machine. Operations under a general state machine are the computational steps of different physical objects, and an operation is ultimately converted into one or more transactions at different block chain systems. Under different block chain systems, the transaction state processed by the consensus algorithm is not necessarily synchronized in time, which causes the problem of inconsistent data, and therefore, constraint dependence needs to be established between operations. To guarantee data consistency, at least two constraint dependencies are required: firstly, pre-condition constraint; and secondly, a timeout condition constraint. A precondition constraint is that an operation with a precondition constraint can be performed if and only if all of its precondition dependent transactions are completed; a timeout condition constraint is an operation that must be completed within a specified time interval given a successful return of execution or a timeout error result, if its dependencies are all satisfied.

The causal effect graph model and the generalized state machine model provide theoretical conceptual models from the angle of formalized language through definition and qualitative analysis of the interconnection and intercommunication problems of the blockchain system, and can develop reasoning of propositions and theorem under the mathematical logic system of formalized language, and can perform formal test on specific capability of the models.

The block chain interconnection theory conceptual model relates to different protocol compositions, and each protocol has its security attribute. The security model of the blockchain interconnection theory conceptual model is determined by the security combination of the constructed protocol clusters, and two problems are involved in the security model: firstly, the security problem of the protocol; secondly, whether the original respective safe protocols can guarantee the safety of the combined protocol after being combined. UC security (Universally Composable Security, universal composable security) is an important tool to solve the protocol combination problem. As a method for certifying security, a whole set of security models is defined in the UC framework to certify the security of the combined protocol in a complex environment. The UC security adopts the modularized thought, and in the UC framework, the protocol proved to be UC security is used as a module in a complex network environment, and when combined with other protocols, the security of the combined protocol is not destroyed, namely, several protocols respectively proved to be UC security in the UC framework are still secure after combination. And combining with the UC safety framework, carrying out mechanism deep analysis on safety factors of the block chain system interconnection and interworking conceptual model, such as abnormality, error, treatment and the like, and designing and proving that the block chain system interconnection and interworking conceptual safety model meets UC safety.

Cross-chain distributed application compilation techniques: intelligent contracts enable blockchain systems to be expanded in their capability boundaries into general purpose computing platforms beyond just one transaction system of digital currency. Blockchain systems play the role of an operating system in the blockchain world, allowing blockchain applications to be created on top of their underlying protocols. The existing blockchain interconnection technology is mainly used for solving the problems of protocols such as cross-chain among blockchain systems, transaction consistency verification and the like, and provides a development interface for blockchain interconnection. When the block chain network of interconnection and intercommunication is needed to be accessed, the service logic codes of the corresponding inter-chain protocols and the codes of specific intelligent contract applications are needed to be developed, which is not friendly to developers, the development flow is complex, and the access cost is high. Most blockchain systems employ different smart contract programming models and different programming languages, such as the ethernet blockchain uses a solubility programming language, hyperledger Fabric supports Go, java, node, etc. multiple programming languages. Intelligent contract cross-chain applications in addition to the differences in programming model and programming language, intelligent contract cross-chain applications are challenging to extend from exchange operations in the digital asset specialty domain to a more general, larger application scope, supporting generic operations. Therefore, the intelligent contract intermediate expression language is researched, language compiling front-end implementation is provided for different languages, and a type mapping system and conversion program of the different languages are established through a unified programming model, so that a developer can use the familiar languages to realize cross-chain access research and development work. The LLVM framework and the ANTLR language identifier technology can be used for providing unified compiling back-end processing programs and processes, providing front-end compiling services for common intelligent contract languages and converting the common intelligent contract languages into intermediate languages. In the conversion process of the intermediate language, static analysis and type checking can be performed to avoid defects and errors in the execution of the cross-chain application.

Block chain interconnection protocol design and realization: the cross-chain interconnection system mainly comprises four components: client programs, transaction execution systems, network state blockchain systems, transaction assurance systems, the architecture diagram of which can be schematically shown in fig. 4.

The client program is a gateway of the cross-chain interconnection system and bears interaction between the distributed application and the cross-chain interconnection system. The distributed application client adopts a lightweight design, so that mobile application and web application can conveniently access and interact with the interconnection system. The transaction execution program acts as a driver for the underlying blockchain, compiles application code provided by the client into a program, and runs and converts the program into transactions that can be executed in the blockchain system. Both the client and the transaction execution system employ inter-chain interoperability protocols to ensure secure execution of transactions in different block chain systems. The inter-chain interoperability protocol is then composed of two parts: the transaction state storage layer and the transaction guarantee intelligent contract. The transaction state storage layer is borne by a network state blockchain system, wherein the network state blockchain is a blockchain in the blockchain, and provides an objective unified view for the execution state of the distributed application. The trade guarantee function contract is responsible for monitoring the execution state and structure of trade and providing arbitrated service for trade. In the event of an anomaly, the transaction assurance intelligent contract will withdraw all transactions performed, return the amount of the transaction to the account of the original party to ensure atomicity of the transaction.

To ensure proper execution of the distributed application, all transactions in the distributed application executable program need to be committed to the corresponding blockchain for execution, and the preconditions and time-limited conditions of the transactions must also be satisfied. The execution of cross-chain distributed applications, while relatively simple in terms of model abstraction, presents a significant challenge in practical execution. Because in an untrusted environment there is no trusted central authority to coordinate sequential execution of transactions on different blockchains, and trust between the client and the transaction execution system is not 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 ensuring execution of the executable program on different blockchains. The inter-chain interoperation protocol is performed by two systems to perform the tasks specified by the cryptographic protocol. The network state data layer is acted by the blockchain system, is responsible for recording the execution result of the cross-chain distributed application and provides a real and objective consistent query view. The network state database organizes the final transactions of the different block chain systems into a merck tree, uniformly describes the final state of the states of the transactions, and provides verifiable evidence. At the same time, the state blockchain system also provides verifiable records for the operation actions respectively executed by the client in the cross-chain transaction execution and the transaction execution, and the function is realized through a behavior consensus algorithm.

The transaction assurance intelligent contract is a code arbitrator, proposes a transaction state verifiable proof from a network state blockchain as input to determine the last execution result of the distributed application, and utilizes a record of operational behavior to determine responsibility attribution for transaction failure.

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

general problem of blockchain interconnection: the blockchain and intelligent contracts executed in the blockchain network may be considered state machine models. The cross-chain distributed application may likewise be abstracted into state machines, maintaining consistency across conceptual models. To achieve this, a unified state model is introduced. Unified state model unified definition and description a cross-chain distributed application is a chain independent, extensible model for describing state transitions between different block chain systems. The unified state model uses a virtual layer to uniformly solve the heterogeneous problem of the underlying blockchain network. This isomerism is reflected in two aspects: the first aspect is the differences in internal structures of the blockchain system itself, such as consensus systems, data structures, etc.; the second aspect is the variability of the smart contract execution environment and programming language. To overcome these two differences, different blockchains are abstracted uniformly into objects with common state variables and functions, and the cross-chain distributed application abstracts the desired operations on these objects and the relative order of execution of these operations.

In formalized language, a unified state model may be defined as m= { E, P, C }, where E is the set of operational 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 that may be used to describe an object defined in a blockchain. The entities have types, each having different attributes, such as account entities and address entities, etc. The operations in the unified state model are calculation steps performed on different pairs of entities, and the entities can belong to the same blockchain or different blockchains. Each operation is ultimately compiled into one or more transactions in a different block chain system. Considering the asynchrony of blockchain transaction execution structure, the unified state model sets up two types for dependencies between operations: a precondition and a timeout condition.

To meet the commonality of interconnection among heterogeneous multiple chains, an inter-chain interoperability protocol is designed based on a common state model. The inter-chain interoperation protocol includes four basic protocols and two phases. The four base protocols are respectively a client-side implemented protocol, a transaction execution system implemented protocol, a network state system implemented protocol and a transaction guarantee intelligent contract implemented protocol. The two phases are a program execution phase and a insurance compensation phase, respectively. During the program execution phase, all transactions in the executable program need to be committed to the corresponding blockchain system. During the guard compensation phase, the correctness and errors of the program execution are arbitrated.

Client protocol and runtime transaction state: during execution of the transaction, the effective state of the transaction is a state set, the last state value is the advanced state of the previous state, and during execution of the transaction, the transaction states sequentially change. For each state, the inter-chain interoperability protocol provides a proof of statement. 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 accomplished through an in-chain state channel. In order to clarify the responsibility of the error in the transaction process, record registration is carried out on the execution steps of each party, and the client and the verifiable program are allowed to be mortgage for the execution steps.

Network state blockchain architecture: the network state storage layer is operated by adopting a blockchain system, and the main purpose is to provide an objective view for the execution condition of the cross-chain distributed application. The network state storage layer selects the blockchain as a design instead of a general database, mainly because of technical characteristics of traceability, non-repudiation, fault tolerance and the like of the blockchain system. The blocks of the network state blockchain contain the necessary fields, hash fields are used to concatenate the blocks, and the merck tree is used to save transactions and state. 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: state root and operation root.

The state root is the merck tree root of the transaction state in the blockchain network. The network state blockchain uses the transaction root and state root of the blockchain to represent the transaction state of one blockchain. Transaction roots and state roots in one blockchain represent the merck tree roots of transactions and the merck tree roots of stored states, respectively. The network state blockchain simply stores the blockchain state associated with the cross-chain distributed application, rather than all of the state of the entire chain, and the basis for determining whether a block is relevant is whether a block in the blockchain has packaged a transaction in the cross-chain distributed executable.

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

The transaction execution system executes a protocol: after the cross-chain distributed application dependency graph is generated, the transaction execution system initiates an execution session. The primary task of the initialization is to create and deploy a transaction execution assurance smart contract to protect the execution of the transaction. To accomplish this task, the transaction execution system first sends a request to the cross-chain transaction support system, creates a transaction execution support smart contract for the transaction dependency graph, and then deploys the transaction execution support smart contract into the network state blockchain after soliciting client consent. In the agreeing process and the execution process of the next transaction, the transaction participants sign the operated object by using the digital signature of the transaction participants to generate certificates, and store the certificates and the transactions in a network state blockchain.

In order for a cross-chain transaction support system to be able to rollback transactions that have been submitted in the event of erroneous execution results, the client program and the transaction execution program need to pay sufficient funds to the transaction support program. As for how much money is to be mortgage, the simplest approach is to calculate the total amount of the transaction, and if a more reasonable and fair ratio is to be calculated, a calculation of the ratio and calculation of the calculation and calculation algorithm of the ratio need to be designed to optimize this step.

After the cross-chain transaction assurance intelligent contract instantiation, the transaction execution system initializes a session daemon to advance the flow of the transaction using different processing functions. When the transaction nursing service of the transaction execution system recognizes that the precondition of the transaction is met, the transaction is triggered to be invoked. In the execution process of the transaction, the client program and the transaction execution system need to sequentially carry out consensus on the execution state of the transaction, then construct the transaction on the target chain based on the logic transaction data, and then submit the transaction to the corresponding target chain. The transaction assurance system can continuously check whether the submitted transaction is completed within a defined time, and then arbitrate the state of the transaction.

Execution of the cross-chain transaction depends on the state of the blockchain network and the state of the transaction state blockchain system. There are two caretaking processes inside the transaction execution program to read the state of these blockchains. The first care process monitors the target chain and queries the status of the submitting transaction by reading the target chain ledger. If the submitted transaction is ultimately 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 also needs to extract the merck proof in the transaction state blockchain to verify the finalization of the transaction execution, which is the second care process.

Transaction execution assurance system protocol: the transaction execution guarantee system generates a transaction execution arbitration code according to the transaction dependency tree and deploys the transaction execution arbitration code into the transaction state blockchain in the form of an intelligent contract. The internal logic of the smart contract will track the status of each transaction in the transaction dependency graph using the transaction status as a parameter. The transaction execution system may continuously invoke the transaction execution assurance system to execute the contract at certain intervals. When the transaction execution is wrong or the transaction timeout occurs, the intelligent appointment execution contract clause performs the rollback and punishment work 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 is mainly focused on the functions of a compiler, and the work of the compiler is divided into a front-end function and a back-end function. Front-end functions include extracting entities, operations, and dependencies from cross-chain applications and extracting public variables and methods of intelligent contracts from blockchain networks. Designing a uniform type system can meet the needs of two aspects: the intelligent contracts written in different programming languages are abstracted into interoperable entities in a unified way; a cross-chain application programmed using a different language may be converted to a unified programming language. The compiler will perform semantic checks on all entities, operations and dependencies to ensure correctness and security of the distributed cross-chain program, and finally, compile the program into an executable program. The organization of the executable program is a transaction dependency graph.

And a 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 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 the unified type is converted into the type supported by the specific blockchain in the dynamic execution process of the program. The design of the unified type system achieves the purpose of unified description and writing for different language types and operations of different blockchains.

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

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

Blockchain interconnect interoperability security issues: the security problem of blockchain interworking is essentially the correctness and security problem of inter-chain interoperation protocols. The inter-chain interoperation protocol may represent its cryptographic protocol abstraction with ideal functionality. Assuming that trusted entities exist, the ideal function states that the correctness and security properties that the cross-chain interoperation system wishes to achieve. The ideal function describes the function of the inter-chain interoperation protocol and the interface definition thereof, including three aspects of transaction session, transaction status update, rollback contract execution. In a transaction session, a client and a transaction execution service request inter-chain interoperation protocol securely execute a cross-chain distributed application. The inter-chain interoperation protocol gives description to the inter-chain distributed application in the form of a transaction dependency graph, and provides a guarantee intelligent contract for transaction execution correctness. As a trusted entity, the inter-chain interoperation protocol assigns a private key to each transaction participant so that they can sign the transaction, computing a certificate. Each participant needs to mortgage sufficient funds to the inter-chain interoperation protocol. The inter-chain interoperability protocol defines a series of interfaces to receive calls from external systems to complete the updating of the transaction state. Inside each interface, the inter-chain interoperability protocol performs the necessary correctness checks to ensure that the transfer of transaction state is legitimate. In all interfaces, the inter-chain interoperation protocol calculates a proof for the corresponding transaction state, and sends the proof to the transaction participants informing the inter-chain interoperation protocol of the actions taken and performed. When timeout occurs, the participants of the transaction can call the interface of the transaction ending to trigger the execution of the transaction assurance intelligent contract code. Based on the final state of each transaction, the transaction arbitration intelligent contract executes transaction arbitration procedures according to a transaction state decision tree, performs responsibility judgment and division of transaction failure, and then performs rollback and punishment of the transaction.

Under the assumption of trust, it is not difficult to infer that the inter-chain interoperation protocol provides the following correctness and security. First, after a specified time period has elapsed, execution of the transaction either ends correctly or fails. The preconditions and execution time limit constraints are satisfied when the end is properly made. When the execution fails, the reverse operation of the transaction is executed to restore the original state. Second, the inter-chain interoperation protocol identifies the responsible party that caused the transaction failure, giving the necessary penalty.

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

asset transplantation: asset transfer may allow a user to transfer his asset from one blockchain to another blockchain. The transfer between blockchains is bi-directional, and at any time the asset can be transferred from another blockchain to the current blockchain.

Atomic exchange: atomic exchange allows two parties to trade with each other and exchange different digital assets in different blockchains. Parties to a transaction need to have accounts or addresses on each different blockchain. Transactions occur simultaneously in all blockchains. Atomic exchanges need to ensure that asset transfers of both parties either occur simultaneously or fail simultaneously. Atomic exchange is also a common transaction mechanism for decentralized transactions.

Cross-chain predictor: the predictor provides external data to the blockchain system. The external data provided by the cross-chain predictor may come from another blockchain. Such as a cross-chain predictor, extracts information about the transaction from the external blockchain and then triggers actions of the smart contract on the local blockchain system to perform the relevant operations.

Asset retention: asset retention is the ability to lock an asset onto a blockchain. When a particular condition is met on another blockchain, the locked asset is unlocked again. For example, the asset placement function may be used on a business that pays security deposit.

Cross-chain intelligence contracts: the cross-chain intelligence contract can seamlessly realize multiple dependencies of the blockchain on other blockchains, thereby realizing the dependency and collaboration of multiple situations. For example, the intelligence of paying a bonus on one blockchain would need to check if the current user is a registered equity holder on the other chain at about the time of paying a bonus. Of course, there are more usage scenarios for cross-chain intelligence contracts.

According to the cross-chain interconnection method of the blockchains, cross-chain interconnection between the blockchains can be conveniently, safely and reliably realized, and especially when the interconnection is carried out between heterogeneous blockchains, transformation of the blockchains 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 blockchain 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 blockchain interconnection theoretical model according to blockchain and a blockchain requirement. The protocol design module 520 is configured to obtain an inter-chain interoperability protocol for blockchain interconnection based on the blockchain interconnection theoretical model. 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 blockchains through the cross-chain distributed application, so as to perform functional verification and protocol evaluation on the blockchain interconnection theoretical model, and implement optimization on the blockchain interconnection theoretical model.

According to the cross-chain interconnection system of the blockchains, which is disclosed by the embodiment of the invention, the cross-chain interconnection between the blockchains can be conveniently, safely and reliably realized, and especially when the interconnection is carried out between heterogeneous blockchains, the transformation of the blockchains can be effectively reduced, so that the cost of the cross-chain operation is reduced.

It should be noted that, the specific implementation manner of the inter-link interconnection system of the blockchain in the embodiment of the present invention is similar to the specific implementation manner of the inter-link interconnection method of the blockchain in the embodiment of the present invention, and specific please refer to the description of the method section, which is not repeated here.

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

The apparatus embodiments described above are merely illustrative, wherein the elements illustrated as separate elements may or may not be physically separate, and the elements shown as elements may or may not be physical elements, may be located in one place, or may be distributed over a plurality of network elements. Some or all of the modules can be selected according to actual needs to achieve the purpose of the embodiment of the invention. Those of ordinary skill in the art will understand and implement the present invention without undue burden.

Claims (6)

1. A method of cross-chain interconnection of blockchains, comprising:

analyzing the blockchain and the cross-chain demand of the blockchain to abstract the blockchain interconnection theoretical model;

the inter-chain interoperation protocol of the block chain interconnection and the inter-chain interoperation and the related mechanism are obtained by taking the block chain interconnection and the inter-chain interconnection theoretical model as a guide, wherein the inter-chain interoperation protocol of the block chain interconnection and the inter-chain interconnection comprises four sub-protocols and two phases, the four sub-protocols comprise 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 respectively, wherein in the program execution phase, transactions in an executable program need to be submitted to the corresponding block chain, and in the insurance compensation phase, the correctness of program execution is arbitrated; the related mechanism comprises a cross-chain transaction verification mechanism, a cross-chain security management mechanism and a unified programming language of a cross-chain intelligent contract;

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

and performing cross-chain operation between two preset blockchains through the cross-chain distributed application so as to perform function verification and protocol evaluation on the blockchain interconnection theoretical model, thereby realizing optimization of the blockchain interconnection theoretical model.

2. The blockchain interconnection method of claim 1, wherein the safety of the blockchain interconnection theoretical model satisfies the safety of the UC safety framework.

3. The method for cross-chain interconnection of blockchains 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.

4. The blockchain cross-link interconnection method of claim 1, further comprising:

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

5. A cross-chain interconnection system of blockchains, comprising:

the determining module is used for analyzing the blockchain and the cross-chain requirement of the blockchain so as to abstract the blockchain interconnection theoretical model;

the protocol design module is used for obtaining an inter-chain interoperation protocol of the block chain interconnection and the related mechanism by taking the block chain interconnection and the related theory model as a guide, wherein the inter-chain interoperation protocol of the block chain interconnection and the related mechanism comprises four sub-protocols and two phases, the four sub-protocols comprise 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 respectively, and transactions in an executable program need to be submitted to the corresponding block chain in the program execution phase, and the correctness of the program execution is arbitrated in the insurance compensation phase; the related mechanism comprises a cross-chain transaction verification mechanism, a cross-chain security management mechanism and a unified programming language of a cross-chain intelligent contract;

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

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

6. A non-transitory computer readable storage medium having stored thereon a computer program, which when executed by a processor implements a blockchain interconnection method according to any of claims 1 to 4.

Images