Research On Privacy Protection Based On Order Preserving Encryption Scheme In Cloud Environment

In recent years,the growing information technology demands promote the development of the high-speed,economical cloud computing technologies,but the problems such as privacy protection caused by the cloud platform which is the untrusted third party.In order to prevent privacy leakage,data owners encrypted information data and stored encrypted information on cloud platforms.Because ordinary encryption can't be used by cloud computing,data owners need efficient encryption algorithms to protect the encrypted data stored on the cloud.The general ciphertext search encryption algorithm only allows simple accurate matching.And for more complex search requests,such as interval search,this kind of algorithm is invalid.So the order preserving encryption algorithm that can make range query directly on encrypted database to protect privacy has aroused the interest of a large amount of researchers.In this thesis,the existing privacy protection schemes based on order preserving encryption algorithms have been analyzed and summarized.A problem has been proposed that how to design a secure and efficient order preserving encryption algorithm for complex search requests of general data to protect privacy.Our works are described as follows:1.The existing privacy protection schemes based on order preserving encryption schemes in cloud environment are classified into three categories and summarized.The existing models of order preserving encryption have been analyzed,and their shortcomings have been pointed out.The security of the privacy protection schemes using the classic order preserving encryption model is low and the security of the privacy protection schemes using tree encryption model is high.In addition,the existing privacy protection schemes have been classified,divided into the invariant ciphertext schemes,the variant ciphertext schemes and the order revealing encryption algorithm.And these privacy protection schemes have been compared and analyzed in various aspects.2.For the problems that the privacy protection schemes based on order preserving encryption can not be taken into account in security and efficiency at the same time,this paper proposed a nonlinear-mapping order preserving encryption scheme to realize privacy protection.To achieve the purpose of hiding the data distribution and data frequency,the scheme is based on the nonlinear-mapping technology to which interference factor is added.The way of nonlinear mapping effectively solves the disadvantage that the enemy obtains the secret key through repeated data,hiding the data frequency.At the same time,the interference factor varies according to the input data value is added to the mapping scheme,which destroys the statistical characteristics of the original data.The way of nonlinear splitting destroys data distribution.These ways improves the security of the scheme.Finally,theoretical analysis shows that the scheme can achieve anti statistical attack and realize IND-DNCPA security.Also this scheme has high efficiency through the simulation results,in which the average encryption execution time of every one hundred thousand encrypted numbers is about 30 ms.3.For the problem that the privacy protection schemes based on order preserving encryption can not support complex query,this paper proposed an order preserving encryption scheme for mutli-keywords query in outsourced column storage.The scheme used the characteristics of the ORE algorithm and can directly output the comparison results through a public functional function called Cmp that performs the comparison operation.The scheme is not limited to the numerical data.The scheme designed an effective multi-keywords query protocol.Users can effectively get the corresponding database information by entering multi-keywords query token.Finally,theoretical analysis show the correctness of the scheme and multi-keywords query protocol.So this scheme can protect privacy well.