Research And Implementation Of File Integrity In A Multi-User Environment

With the fast development of cloud computing,it brings us so much convenience to our daily life.But it also has some secure risks on the data which stored in the cloud servers.The paper research how to verify the update documents verifiably in a multi-user environment and how to distinguish incomplete search results from incomplete document sets around the cloud server,the work mainly includes the following three aspects.In a Dynamic Verifiable Searchable Symmetric Encryption(DVSSE)scheme,a client Alice can not only perform keyword-based searches on ciphertexts,but also update(modify,delete and add)documents in a verifiable way.However,the DVSSE scheme is not suitable for the multi-user environment.The reason is that it is hard to achieve traceability if all users share the symmetric key with Alice.In this paper,we propose a Multi-user Dynamic Verifiable Searchable Encryption(MDVSE)scheme,which utilizes the Proxy Re-Encryption with keyword Search(PRES)scheme to enable multiple users with different keys to perform keyword-based searches update and verifications on the document set.The authorized users can also efficiently update(modify,delete and add)ciphertexts and verify the integrity of the file set.we confirm that our proposed schemes can work as efficiently as the DVSSE and protect the privacy of keyword,files and verifiable proof.Based on our proposed scheme,we extend the verification of our scheme.We apply the Merkle Hash Tree(MHT)to achieve integrity verification on both search results and document set.We compute the index of keywords and files as the leaf nodes of the Merkle Hash Tree as the new verifiable proof.If the first verification fails,our scheme will do the second verification.Besides that,we extend DVSSE scheme by using the signature technology to achieve the traceability.We analyze the security and performance of the proposed scheme,and conduct extensive experiments to verify its feasibility.Based on the MDVSE algorithm,we designed a cloud storage services system,and we applied the MDVSE algorithm into our system.We did demand analysis,database design and system design of our system.