Research On Blockchain Identity Privacy And Data Privacy Protection Mechanism

As an emerging distributed ledger technology,blockchain has the characteristics of openness,transparency,recordability and traceability.Transaction records and privacy data among users are stored in blockchain,which are maintained by all peers in the system.Combined with the Internet of Things,finance,medical and other industries,blockchain technology is developing rapidly and the scale of the industry has become larger.The data on the blockchain is public to peers of the whole network,which will leave lead to the leakage of user information.With the development of blockchain technology,the anonymity and privacy inherent in the blockchain cannot meet the user's need for privacy protection anymore,so there is an urgent need for new solutions to protect data privacy and user privacy.In view of the security and privacy issues in the blockchain,this thesis has carried out research on key technologies such as identity privacy and data privacy protection.The concrete works of this thesis are as follows:First of all,this thesis takes the security and privacy issues existing in the blockchain as the research object,and analyzes the various levels of the blockchain.We summarize the privacy issues in the blockchain as data privacy and identity privacy.Based on the issues of identity privacy and data privacy,the existing privacy protection schemes are introduced and the characteristics of each scheme are analyzed and compared,which provides a direction for further enhancing the privacy protection capability of blockchain.Secondly,aim at the transaction privacy problem and identity privacy problem existing in the blockchain privacy protection scheme,the transaction privacy enhancement scheme is constructed by combining blockchain transaction,aggregate signature and group signature.Group signature algorithm is introduced to protect user's identity privacy.The transaction user submits the transaction information and requests anonymously in the user group,which protects the user's identity privacy.The aggregate signature algorithm is introduced to disrupt the correspondence between transactions and protect the transaction privacy in blockchain.The signatures of transaction users are aggregated into one signature to improve the efficiency of signature verification,so that the block can contain more transaction records.To some extent,the problem of limited block capacity can be alleviated.Atthe end of the scheme,we present the transaction privacy enhancement model and prove the security of the scheme based on the random oracle model and the CDH difficulty problem.Finally,aiming at the privacy leakage problem of blockchain data,a blockchain-based data encryption and retrieval privacy protection scheme is proposed,which improves the privacy protection mechanism of blockchain.The scheme uses the public key of the data querier to encrypt the data and provide the ciphertext retrieval function.Only the data querier with the corresponding private key can decrypt the ciphertext and protect the user's data privacy.In order to improve the query efficiency of data on block chains,we map keywords to Bloom filters.Information retrieval can be accelerated and users can quickly obtain data of interest by matching bloom filter with keyword trapdoor.In addition,in order to alleviate the storage pressure due to the limited block capacity,the scheme only stores the index information on the blockchain and stores the ciphertext in the external server.