Research On Several Key Security Issues Of Data Stored In Cloud

In cloud storage system, users can outsource their local data to the cloud servers to lighten local storage and computing resource loads, which products a new method of use-on-demand, pay-for-use, and self-service. However, outsourcing data to cloud servers makes sensitive information centralized into the server, which brings great challenge to protecting sensitive information privacy.Cloud storage service provider is not honest to users. Once users outsource their data to cloud servers, they lost direct physical control to the remoted data. This operation brings following problems:(1) User can not certain whether the outsourced data is stored correctly and is not corrupted by illegal adversary;(2) For privacy preserving, user may encrypt the local files and then upload the cipher-text to cloud server, thus user need a effective method that complete keyword searching over cipher-text, retrieving and decrypting the encrypted data operations. For the two security problem in Cloud storage, data verification and searchable encryption, the article takes a deep research and proposes the responding algorithms.For data verification, we propose an efficient scheme that allows verification of the quality of the data and also supports dynamic data operations. The scheme supports public verification, that the users can delegate the verification task to a third party. And it is based on bloom filter and Merkle hash tree, thus the overhead of noth storage and computing cost is very small. And for searchable encryption, we systematically propose a new scheme to solve the problem of how to securely and efficiently retrieve the Top-N files by keyword-based searching over encrypted data. In the approach, the Cloud servers can only obtain secure index, cipher-text, trapdoor, but cannot obtain anything else based on the index, cipher-text and trapdoor. Finally the performance analysis shows that the scheme is more efficient than other proposed schemes.