Research And Design Of Searchable Public Key Encryption

In order to reduce the cost of data maintenance, more and more companies and individuals choose to store their data on the server of the third-party to enjoy the convenient and flexible data service provided by service provider. Howerver, the third-party server is not entirely credible. To prevent user data from being leaked, the general practice is to encrypt user's data firstly before uploading them to the server of third-party. However, the traditional data encryption technology makes the data cannot be retrived and it is queit inconvenient for users. The proposed searchable encrytion made this issue solved.Searchable encryption mechanism can be generally devided into two categories: symmetric searchable encryption and asymmetric searchable encryption. In this thesis, the work mainly foucus on the research and study of asymmetric searchable encryption.Since the safety and efficiency of the existing schemes still have gap between the practical requriement. Therefore the mainly work of this thesis is to propose more efficient schemes based on existing schemes which can meet the actual need better. The fulfillment work of this thesis mainly including the following aspects:1. A multi-key searchable encryption scheme with designated server is proposed in this thesis. In multi-user environment, user data sharing is an important issue. However, among the existing sechemes with designated server almost no one has considerd this issue. In this new proposed scheme, different file encryption keys are used to encrypt different files to improve the security of user data and in this way it can prevent the attack from the malicious users. Meanwhile document encryption key is embedded into the keyword ciphertext to achieve user access control. When the keyword which user query for included in different files, there is no need to generate different trapdoors aim to different fiels. Through this way it can avoid the problem that the number of trapdoors is linearly growing with the number of encryption keys. Finally, through security analysis and experiment it illustrates the safety and feasibility of this scheme.2. A timed-release searchable encryption scheme with a designated server is proposed in this thesis. In this scheme, timed-release technology is applied to searchable encryption which achieved the function of user timing retrieval. It is means that only arrived at the designated time can the user search successfully. At the same time, in this new scheme, user also can designate a retrieval server which is trusted to execute its query. Meanwhile, through security analysis and experiment it illustrates the safety and feasibility of this scheme.