| Blockchain is a shared digital public ledger that cannot be changed once a transaction has been recorded and verified.Since most blockchain nodes retain a copy of the ledger,it brings decentralized benefits to the blockchain and also leads to privacy leak issues.This paper studies the privacy of blockchain transaction data and main work is as follows.With regard to the privacy protection of blockchain transaction address,this paper proposes an improved coin mixing scheme based on Xim and develop a wallet application with this feature.There is no centralized third-party participation in the matching and mixing process of the improved solution.Matching process:using anonymous advertisement to find the coin mixing users who have the willingness to mix fixed amount of funds.Mixing process:using shuffling operation to scramble the connection between the input and output addresses.All users check whether the input and output address set contains its own address and sign the transaction.When the transaction is signed by all users,the transaction is sent to the blockchain network.According to results of the analysis of security and experimental test,the improved scheme reduces the time of coin mixing,and solves the security problems such as time attack and inference attack in Xim.With regard of the privacy protection of blockchain transaction data,this paper proposed a new scheme which mainly uses a zero-knowledge proof named Bulletproof.And this paper optimized Bulletproof by multi-scalar multiplication in elliptic curve.The results of experimental test of scalar multiplication algorithm show that the improved algorithm generates KG faster and increase the speed of proof generation and verification when the scalar multiplication coefficient K is big.The security analysis of the program shows that the scheme solves the problem of double-spend,payment authorization and dishonest miners.While protecting the data privacy of the blockchain transaction,the blockchain performance is improved. |
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