Interaction Schemes For Cross Blockchain Systems

Nowadays,changes led by information technology have had a huge impact on society and the economy.Blockchain is the innovation force of a new generation of information technology and an important breakthrough for the independent innovation of China's core technology.As one of the key industries of the digital economy,it has also been included in the outline of the14 th Five-Year Plan for the National Economy.Blockchain constructs a new data structure that is unforgeable,unchangeable,and traceable through transparent and trusted rules in peer-topeer network environment,which is the foundation of a new distributed business.Its application has expanded from digital currency to supply chain management,financial insurance,digital copyright,education,Internet of things,intelligent manufacturing,and other social fields.With the development of blockchain technology and economy,the demand for data interaction and application collaboration between blockchain is increasingly emerging.In the context of enterprise level alliance chain,cross-blockchain technology is not only responsible for the transfer of data,but also to get through the cooperation network and cross organization business process behind different blockchain networks,so as to improve the cooperation efficiency among enterprises related to different blockchains.Restricted by the differences in data structure,interface protocol,consensus mechanism,and even business model,a new "chain islands" have been formed between blockchain applications,which directly limit the interoperability of asset exchange and business collaboration between blockchains.Based on the full analysis of the technical characteristics of blockchain and the development needs of blockchain Internet,this paper will study the cross-blockchain interaction architecture,crossblockchain asset exchange mechanism,cross-blockchain user unified identification,etc.,and carry out experiments and verification on the prototype of the cross-blockchain system.The main contributions of this thesis are summarized below.(1)Research on interaction architecture of cross-blockchain system,and propose a multilevel and multi-chain blockchain interoperability architecture.Starting from the five-layer architecture model of blockchain,including data layer,network layer,consensus layer,contract layer,and application layer,this paper studies and analyzes the hierarchical structure of cross chain interoperability,and deeply analyzes the implementation mechanism of cross-blockchain communication mechanism,consensus mechanism and smart contract collaboration mechanism.Meanwhile,the development stages of single-chain expansion,multi-chain crossblockchain and multi-level multi-chain cross-blockchain are analyzed.This paper proposes a multi-level and multi-chain blockchain interoperability architecture,studies the cross-blockchain component model and the functions of cross-blockchain adapter,gateway,registry and relay chain,and deeply analyzes the interaction protocol stack of cross-blockchain,so as to realize the encapsulation,transmission and interoperability control of cross-blockchain messages.(2)Research on multi-hop asset exchange based on notary and hash-lock,and propose a notary evaluation mechanism and multi-hop cross-blockchain asset exchange method.Aiming at the problem of insufficient node credit supervision of the cross-chain notary mechanism,through comprehensive analysis and mutual verification of user evaluation and node information,a notary node trust evaluation model and an improved Page Rank based node evaluation algorithm are designed.On this basis,a new model of multi-hop asset exchange supporting cross-blockchain is proposed.The security of traditional hash-locking mechanism is improved by notary multi-signature algorithm.The detection method of multi-hop transaction loop and multi-key negotiation algorithm are designed,and the key is used as the condition of multisignature locking and unlocking,thus the multi-hop cross-blockchain asset exchange capability is realized.Based on the above methods,a three-stage cross-blockchain transaction process of key agreement,asset locking and asset unlocking is designed.The combination of notary and multi-signature solves the problem of signature collusion between notary and user,and improves the credibility of cross-blockchain asset transactions.(3)Research on user identification and contract execution key technologies for crossblockchain interaction,and propose the execution method of cross-blockchain smart contract and the distributed unified identification mechanism of cross-blockchain users.Combined with the requirements of cross-blockchain asset exchange and data interaction,by designing the basic operation primitives,a coordination mechanism cross-blockchain smart contracts is proposed,and the cross-blockchain contract execution is defined as two-stage and four-stage protocols.The cross-blockchain transaction and transaction verification are carried out by the block head synchronization contract between the cross-blockchain system and the participating chain,so as to ensure the authenticity and reliability of the cross-blockchain information.Meanwhile,combined with the needs of cross-blockchain,a distributed unified identity scheme for multi-source heterogeneous blockchain is proposed.The identity association of the same user in different blockchain systems is realized by relational mapping,and Zero-knowledge proof protocol and digital signature are introduced to realize user's cross-blockchain access function and protect user's identity privacy in cross-blockchain system.