Researching Of Efficient Designated Verifier Signature Scheme And Application

Cloud computing provides a great platform for the application, more and more sensitive information are being centralized into the cloud, such as emails, personal health records, government documents, etc. By storing their data into the cloud, the data owners can be relieved from the burden of data storage and maintenance so as to enjoy the on-demand high quality data storage service. But in the process of using its service, the interests of the users may be damaged. Because when the cloud platform maintain and manage the data, it may maliciously damage the confidentiality and integrity of users` data. A general method of solving this problem is to encrypt users’ data files, and CSP(cloud server provider) search for specific keywords to return the documents to meet the needs of users. The server can’t get any information from the encrypted documents. Because of the importance of encryption with keyword search, in the thesis, encryption search scheme and its applications were studied. The main contributions of this thesis are:1. This thesis reviews those researches of encryption search schemes. It describes the basic concepts of encryption search scheme, the formal definition, security model, security characteristic, and commonly mathematic tools. The classical encryption search scheme and the design principles of the El Gamal encryption were analyzed in-depth.2. After studying the cryptosystem of public key encryption with keyword search, the design principles of the secure-channel free scheme were analyzed in-depth. The basic ideas of the scheme is that is to make the server to keep its own private and public key pair. In order to create a PEKS ciphertext, the sender uses the server’s public key as well as the receiver’s public key. The receiver then can send a trapdoor to retrieve data associated with the encrypted keyword as usual, but at this time, he can send it via a public channel. Upon receiving the trapdoor, the server can test whether given PEKS ciphertexts match the trapdoor using its private key. because the overhead is very huge of an idealized secure channel in the random model.3. The current existing public key encryption search scheme easily is subjected to keyword guessing attack. This thesis presents a trapdoor-indistinguishable public key encryption with fuzzy keyword search. This scheme can be not only aganist keyword guessing attack but also support the fuzzy keyword search on the premise of public key encryption. This scheme is more efficient than other schemes in the availability, and there is no security cut back.4. After studying the El Gamal encryption algorithm in-depth, this thesis proposes an El Gamal encryption with fuzzy keyword search. the proposed scheme is constructed on the El Gamal encryption instead of the bilinear-pairing encryption, which greatly improve the computational efficiency. Meanwhile, the scheme our scheme not only supports accurate keyword search encryption but also supports the fuzzy keyword search, the searching performance of it is better than others.