Privacy Protection Method For Electronic Certificates Based On Blockchain

With the rapid development and promotion of "Internet +" and smart cities,electronic certificates as an important data certificate have brought great convenience to people's lives.However,electronic certificates also have many security problems.Most electronic license databases are stored in cities or provinces,which have the potential security risks of data damage and information leakage caused by malicious user attacks on storage servers,and there is also the potential risk of sudden natural disasters that may lead to storage data loss;what is more worrying is that the electronic certificate system generally uses plaintext to store data,and the user's identity and certificate information are at a glance,which seriously leaks the user's privacy.In this paper,we use the characteristics of blockchain decentralization and nontampering,the blockchain is introduced into the privacy protection of electronic certificates to effectively enhance the security of data.In order to protect the privacy of electronic licenses,this paper proposes a blockchain-based privacy protection method for electronic licenses,which mainly uses attribute-based encryption to store user license data,and combines searchable encryption mechanisms to achieve ciphertext data retrieval,This article gives the relevant models and algorithms in detail.First,the IPFS is used to store the certificate ciphertext,and the attribute-based encryption mechanism is introduced to process the encryption key and keyword set and store them in the Ethereum blockchain transaction.The pseudo-random identity is encrypted and stored in the smart contract together with the block number of the blockchain transaction.Then the license holder generates a search token according to his own identity,The token is sent to the license user through a secure channel,and the holder or user broadcasts the search token to let the searcher on the blockchain call the smart contract.After calculation and verification,the searcher will return the Ethereum transaction block number if the verification is successful.Finally,the user decrypts the data according to his own attribute key.Only the user whose attributes meet the access policy and the key set is correct can decrypt the encryption key,and then restore the original information of the license.The security of the model and algorithm was proved and analyzed from the theoretical and experimental aspects.The security hypothesis was used to theoretically prove the feasibility of the method in this paper,and the security of the model was analyzed;through the Ethereum test a simulation experiment was carried out on the network,and the related Gas cost was calculated.At the same time,the performance of the searchable encryption method in this paper was compared with the methods in other documents in multiple stages using a programming language.Experimental results show that the system in this paper can effectively ensure data security and has high performance in protecting user data privacy.