Research And Implementation Of Key Technologies For Multi-Channel Consortium Blockchain

Blockchains are getting more and more popular recently due to its promising features,especially the decentralized architecture.According to the use cases,blockchains can be classified into three categories: public blockchain,consortium blockchain,and private blockchain.To be able to be deployed in totally untrusted and open environments,distributed consensus mechanisms in public blockchains suffer from sever resource waste and poor performance.However,practical applications usually raise intense demands for performance,access control,as well as privacy.In the meanwhile,it is easy for participants in practical applications to build trust relationships,so by designating particular ones to maintain the ledger,consortium blockchains can provide better permission control,privacy protection,and improved throughput compared to public ones.As a typical consortium blockchain,Hyperledger Fabric is the first to propose the multi-channel architecture,providing a security model for identification,auditability,and privacy protection.However,the architecture is so complicated that it is hard to deliver compelling throughput.Additionally,Fabric does not support cross-channel transactions,which are of great importance for consortium blockchains.There is also potential information leaking introduced by its read-write set-based transaction validation design.Finally,Fabric only provides CFT consensus protocols,while BTF consensus is mandatory for applications in limited trust environments.To address these challenges,this thesis proposes an enterprise-oriented multi-channel consortium blockchain,XLedger.By leveraging the typical “order-excute” and Fabric's“execute-order-validate” architectures,XLedger is designed to be flexible and modular to guarantee the overall performance along with efficient access control and strict privacy management.The major contributions are as follows:1.Multi-channel architecture.Multi-channel is critical for communication isolation and data confidentiality.It also enables the blockchain system to support several parallel chains simultaneously.XLedger also provides a dedicated channel to maintain the total-order information of blocks from all channels,which is essential for cross-channel transactions in consortium blockchains.2.Pluggable consensus protocol framework.XLedger devises a pluggable consensus protocol framework to help the ordering module to address the limitations of the fixed trust model and hard-coded consensus in most blockchains.Besides the typical CFT protocols,XLedger also supports BFT,which results in three consensus algorithms,Solo,Raft,and Tendermint.Therefore,real-world applications could configure to use the appropriate consensus protocol for the ordering module considering the real trust model.3.SM-cryptographic algorithms support.The requirement for information confidentiality and security in consortium blockchains is getting higher and higher.However,there are various practical challenges for traditional cryptographic algorithms.Moreover,the deployment of consortium blockchains is also subject to the compliance and regulation of local authorities.Therefore,XLedger is designed to support different cryptographic algorithms,and the national cryptographic algorithms,SM2 and SM3,are implemented from scratch aiming for excellent performance compared to their counterparts,GmSSL-Go and gmsm.The prototype of XLedger is implemented with Golang and evaluated extensively in a distributed environment.The experimental results in terms of the number of ordering nodes,the number of channels,the batch size,and the batch time,indicate the effectiveness of the design.