Research On Scalability And Privacy Protection Strategy Of Blockchain-based Access Control Model

The internet of things accelerates the aggregation and sharing of resources and data in the Internet of Things(Io T),making it one of the infrastructures in many fields such as smart city.Access control has become an important means to protect user privacy in Io T.However,the existing access control models for Io T,whether centralized or distributed,have some shortcomings,such as single point of failure,resource limitations of Io T devices.Blockchain has the characteristics of decentralization,unforgeability,open sharing and anonymity.The emergence of blockchain technology makes it possible to provide a distributed and secure access control model for Io T.Because each blockchain node needs to store all blocks,and in order to ensure the data consistency between nodes,only one block will be mined in the network at the same time,which makes the transaction processing rate of the blockchain unable to bear a large number of transactions in Io T,and the nodes will also face huge storage pressure.In addition,anonymity in the blockchain is guaranteed by anonymous addresses,which are used to disconnect users from transactions.However,the attacker can easily break the anonymity by performing clustering analysis on anonymous addresses,thereby associating all transaction data of the same user and compromising user privacy.Aiming at the scalability of blockchain-based access control model,this paper analyzes the factors that affect the transaction processing speed.A scalability scheme based on the network sharding is proposed to divide the network into multiple local blockchain networks and one global blockchain network.Multiple blockchain networks run in parallel to improve the transaction processing rate.Each transaction is processed and stored by one blockchain network according to the transaction sharding scheme.Therefore,the storage pressure of nodes is reduced by transaction sharding,and the scalability of blockchain-based access control model for Io T is improved.Comparing the experimental results,in the scalability scheme based on the network sharding,as the number of sharding networks grows,the transaction processing rate and storage cost of each node show linear growth and decrease,respectively.This paper explores privacy protection problem in blockchain,and presents a new privacy protection strategy based on the storage structure of the Bloom filter to obfuscate the attacker's sharding decision on transactions with the aid of Bloom filter's misjudgment.In this paper,the unidirection of the hash computation and the diversity of Bloom filter field combinations ensure the anonymity of transactions by using Bloom filter field to replace the anonymous addresses in the transactions,which solves the problem of anonymous address clustering analysis.It is formally demonstrated that the Bloom filter-based privacy protection strategy has transaction indistinguishable security by constructing the attacker model of transaction indistinguishability in the local blockchain.The experimental results show that,compared to the network sharding scheme,the privacy protection scheme increases the storage of nodes in the local blockchain network due to misjudgment resulting in part of cross-shard transactions being stored on the local blockchain.However,in the worst case,the privacy-protection scheme still ensures the scalability of the blockchain-based access control model.