Research On Searchable Encryption And Data Integrity Auditing Based On Certificateless In Cloud Environment

The emergence of cloud storage has provided a lot of convenience for users to collect,store and share data.However,The confidentiality and integrity of data stored on the cloud cannot be ensured due to the fact that third-party providers are responsible for providing cloud storage.With searchable encryption,it is possible for users to search for specific information within ciphertext,which not only efficiently utilizes ciphertext but also safeguards data privacy.Data integrity auditing allows users to verify the integrity of data efficiently on cloud servers.However,on the one hand,most of the existing searchable encryption schemes are unable to resist keyword guessing attacks and do not support flexible authorization;on the other hand,a great majority of the existing data integrity auditing schemes are limited to single-user scenarios and cannot meet the needs of group shared data integrity auditing.At the same time,most existing schemes are based on public key infrastructure or identity-based cryptography,which has certificate management and key escrow problems.To ensure the security of data stored in cloud storage and address the aforementioned issues,this thesis extensively explores the use of searchable encryption and data integrity auditing methods based on certificateless public key encryption.The thesis primarily covers the following topics in detail.(1)Aiming at the problem that most certificateless searchable encryption schemes are not secure enough in the face of keyword guessing attack,we propose a secure certificateless public key searchable encryption scheme.Firstly,Wu et al.’s scheme is analyzed,and it is pointed out that their scheme cannot resist multi-keywords guessing attack and online keyword guessing attacks.Secondly,a certificateless searchable encryption scheme that can resist online keyword guessing attack is proposed.Moreover,our scheme satisfies multi-trapdoor privacy,and the adversary cannot obtain the linkage between different trapdoors.Finally,based on the CBDH problem,a formal security proof is given under the random oracle model.The simulation experimental results show that our scheme performs well.(2)To solve the problem that existing certificateless searchable encryption schemes can not support flexible authorization,we propose a certificateless searchable encryption scheme that supports fast and flexible authorization.The scheme provides flexible authorization for accessing permissions on data receivers by constructing authorization keys.In addition,the scheme supports conjunctive keyword search,keyword subset search,etc.The security analysis shows that the scheme can protect users’ data security,and the performance evaluations demonstrate the overhead of proposed scheme are modest.(3)To solve the problem that existing group data integrity auditing schemes cannot resist collusion attacks,we propose a certificateless group shared data integrity auditing scheme that resists collusion attacks.By adopting the key update strategy,user revocation in the group is well supported,which not only reduces the communication and computation overhead,but also achieves the resistance to collusion attacks.By randomly blinding the integrity proof,the cloud server protects users’ sensitive data from being accessed by third-party auditors.Finally,the security of proposed scheme has been formally proved in the standard model,and the simulations demonstrate that the scheme has a low computation and storage overhead.