| Blockchain is a distributed shared ledger and database,which has the characteristics of decentralization,immutability,traceability,openness and transparency.Blockchain technology has promising applications in areas such as finance,Internet of Things,logistics,public services,digital rights and insurance.However,on the one hand,the scalability problem of blockchain hinders its large-scale application,especially in the scenarios with large-scale network nodes such as the Internet of Things.Block chain,on the other hand,transparency can directly lead to the leakage of users' privacy,through the analysis of the data on the block chain,can infer the user's personal privacy information,such as the account balance and transaction records,such as block chain privacy issues also become the obstacle of its application in some areas,especially in the field of data sharing and so on is sensitive to the data.It has become an important work to solve the problems of blockchain extensibility and privacy protection.Industry and academia have come up with a number of solutions to the scalability problem.In particular,the emergence of sharding technology has made it the first choice to address blockchain scalability issues.By dividing the blockchain network into several subnetworks that run concurrently among each other,and each subnetwork handles a portion of the transactions,the throughput of the entire network is increased.At the same time,in view of privacy protection,more and more privacy protection technologies are applied to blockchain,such as group signature,ring signature,homomorphic encryption and zero-knowledge proof technology.Although there are more and more solutions to the scalability and privacy issues of blockchain,the current solutions are difficult to achieve both,that is,to solve the scalability and privacy protection issues in the blockchain at the same time.Based on zero-knowledge proof technology,this paper designs a privacy protection scheme for a highly scalable hierarchical multi-chain blockchain:Hypermaze.The scheme uses zero-knowledge proof technology zk-SNARK as privacy protection technology to realize an identities-based double balance account model.The single balance of the traditional account is divided into clear balance and private balance,and the two-stage transfer mechanism(2PXT)is used to realize the anonymous intra-chain and cross-chain transactions.This scheme preserves the high scalability characteristics of hierarchical blockchain system while protecting user privacy.In addition,this article provides a detailed construction scheme for the HyperMaze,from the design of the data structure to the specific algorithms involved in the transfer process and the corresponding zero-knowledge proof circuit diagram.At the same time,a security model is developed for the Hypermaze protocol under the framework of UC(Universal Composability),and a strict formalized security proof based on simulation is given under this model.Then,the privacy and integrity of the system are discussed in detail.Finally,the HyperMaze scheme was implemented based on the Go-Ethereum source code and Libsnark,the zk-SNARK implementation library,and a series of experiments were conducted to evaluate the individual algorithms and overall system performance by building a large-scale blockchain network with up to 2,600 nodes.The results showed that a HyperMaze system with a system depth of 4,a branch count of 6 and a threshold of(7,10)could achieve a throughput of 19440 TPS with a transaction confirmation delay of just 9.5 seconds.This shows that HyperMaze has the characteristics of high efficiency and low delay.Hypermaze is the first privacy-preserving blockchain system to achieve 19,000 TPS,demonstrating its strong privacy protection capabilities and high scalability. |
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