Research On Data Privacy Protection In Blockchain

Since the concept of blockchain was put forward by a scholar named Satoshi Nakamoto in 2008,it has attracted high attention due to its characteristics of decentralization,trustworthiness,immutable and unforgeable,and has broad application prospects in digital currency,finance and other fields.With the widespread circulation and rapid development of Bitcoin,turing-complete blockchain platforms for users to program have gradually emerged,making blockchain technology gradually enter the era of smart contracts.However,in the practical application of blockchain,the completely transparent ledger makes the data on the chain open to all members,and the issue of privacy protection gradually becomes a new challenge.On the one hand,the consensus node needs to verify the validity of blockchain transactions through the transaction information recorded in the ledger.Fully transparent ledgers,on the other hand,expose users’ transactions and even identities to all members.For blockchain represented by Bitcoin,privacy issues can be divided into two types,namely identity privacy and transaction privacy.For blockchain represented by smart contract,privacy issues can be divided into two types,namely,smart contract code privacy and input and output data privacy.In view of the privacy problems in blockchain,researchers have proposed a series of solutions based on homomorphic encryption,ring signature and other technologies,but these solutions have shortcomings such as incomplete consideration of privacy problems and weak performance.Therefore,in order to solve the privacy problems in blockchain,this paper proposes corresponding solutions.The specific research contents are as follows:Firstly,a dual privacy protection method based on group signature and homomorphic encryption is proposed for the federation chain and account-based blockchain model.Based on the characteristics of group signature and homomorphic encryption,the double privacy protection of user identity and transaction amount is realized on the premise of meeting the requirements of verifiable transaction validity and availability of transaction data.In addition,a four-step verification method for the main nodes is proposed to verify the transaction under the premise that the transaction data and user identity are not visible by the proof of the group signature,account ownership and transaction amount.The four-step compact verification can resist tampering attack and public key replacement attack,and has high security.Finally,a new block transaction writing structure is proposed to reduce the block length of a single transaction and improve the block utilization.Then,in order to protect the privacy of input and output data during the operation of smart contract,a smart contract model for privacy protection based on secure multi-party computation is proposed.The scheme inserts a secure multi-party computation layer without affecting the original structure of the smart contract to protect the privacy of the smart contract input and output.In addition,based on(t,n)threshold secret sharing,a random selection strategy of computing participants is designed to resist collusion attacks by randomly selecting nodes that participate in secure multi-party computation.Finally,cryptography is used to encrypt the private data and reduce the possibility of privacy disclosure,which has the characteristics of correctness of computing and privacy and anticollusion.Finally,aiming at the problem that cryptography method is difficult to be applied to smart contract due to its construction difficulties,low efficiency,low occupancy of blockchain storage space and other shortcomings,a privacy protection efficient smart contract model based on trusted execution environment is proposed.Based on the trusted execution environment,the operation process of smart contract is completely carried out in TEE,and the input-output privacy and code privacy of smart contract are guaranteed.Verifiable random functions are used to randomly select operation nodes executing smart contracts to reduce the possibility of collusion between dishonest operation nodes of smart contracts and further improve the privacy and security of smart contract operation.Finally,combining a schema ledger based on directed acyclic graph(DAG)that supports block concurrent operations with a high-performance trusted execution environment,the throughput of the model increased by 34% compared to traditional ledgers.