Research On Key Technologies Of Transaction Security And Privacy Protection In Blockchain

Blockchain technology is a decentralized distributed database technology,which has the characteristics of de-trust,transparent transaction,data cannot be tampered with.It can effectively reduce data management cost,improve work efficiency and protect data security.However,with the development of quantum computing,the quantum computing attack with strong computational power can solve the classical cryptography algorithm,which poses a great threat to the transaction security of blockchain relying on elliptic curve digital signature algorithm.Meanwhile,due to the transparency of transaction information in blockchain,relevant research has proved that there is still a risk of identity privacy leakage.Therefore,the research on the security and privacy of blockchain transaction has become an important topic in the field of blockchain security.This thesis aims to improve the security and anonymity of blockchain transaction.Aiming at the security problem that the signature algorithm of blockchain transaction can not resist quantum computing attacks and identity privacy leakage,the key technologies of blockchain transaction security and privacy protection are studied.The main contributions of this thesis are summarized as follows.(1)Aiming at the problem that the signature algorithm of blockchain transaction can not resist quantum computing attacks,a post-quantum blockchain scheme based on lattice signature algorithm is proposed.In this scheme,a signature algorithm is designed by using lattice basis delegation algorithm and preimage sampling algorithm.The signature algorithm is introduced into the blockchain technology for signing and verifying blockchain transactions.After security analysis,the signature algorithm in this blockchain scheme satisfies the requirements of correctness and unforgeability.At the same time,based on the difficulty of small integer solution on lattice,this signature algorithm can improve the security of blockchain transaction and solve the problem that signature algorithm in blockchain can not resist quantum computing attacks.Compared with other lattice signature algorithms,the experimental results show that the lengths of user's public key and private key in this scheme are shorter,and the signature length is reduced by 50%,which is beneficial to improve the efficiency of signing and verifying blockchain transactions.(2)Aiming at the security problem of identity privacy leakage in blockchain,an anonymous post-quantum blockchain scheme based on linkable ring signature is studied and designed.A linkable ring signature scheme based on lattice is designed by using the trapdoor generation algorithm on lattice and the principle of rejection sampling.The linkable ring signature scheme is introduced into the transaction of blockchain,and the anonymous post-quantum blockchain scheme is designed by using the principle of stealth address and key image.This scheme can hide the identity information of both parties and solves the risk of privacy leakage of traditional blockchain users.The security of the scheme is analyzed under the random oracle model,and it is proved that the ring signature algorithm in the scheme satisfies the correctness,anonymity,unforgeability and linkability.Compared with other ring signature schemes,the experimental results show that the length of key and signature is shorter,and the communication computation overhead and completion time are less.Compared with Zerocoin and Monroe schemes,this proposed scheme not only provides privacy protection for user identity,but also has the security advantage of resisting quantum computing attacks.(3)Aiming at the fact that users'privacy information is easy to be leaked and abused,and the traditional information access control has the problems of data bloated and low security,this thesis studies the information access control scheme based on cloud storage and blockchain.In this scheme,using cloud storage technology,personal information is stored in the form of ciphertext in cloud server to protect user privacy information.And its hash value is stored on blockchain.At the same time,the smart contract is used to automatically trigger the operation of personal information access to prevent the user's privacy information from being leaked or abused by others,which is more efficient and secure.Compared with FairAccess and other schemes,the user information is encrypted and stored in the cloud server,and the blockchain only stores the hash index of the information.It reduces the cost of information storage and management of the blockchain,which is conducive to improving the operation efficiency of the blockchain.(4)Based on quantum entanglement and Delegated Proof of Stake(DPoS)consensus mechanism,a secure quantum blockchain scheme is presented.In this scheme,the quantum coin in the form of quantum state is designed to be used as the cryptocurrency in blockchain transactions.Based on the quantum no-cloning theorem,quantum coin can not be copied which can resist the double spending attack in blockchain.Combined with quantum entanglement principle and quantum key security distribution protocol,quantum key is used for signing and verifying blockchain transaction to protect the security of user transaction and privacy information.In this scheme,the maximum entangled Bell state is used to realize quantum block coding,and the DPoS consensus mechanism is used to achieve quantum blockchain consensus.The security analysis shows that this scheme can resist the man-in-the-middle attack,eavesdropping attack,double spending attack,state estimation attack,which improves the security of blockchain transaction and privacy information.