Design of a Certificateless Designated Server Based Searchable Public Key Encryption Scheme
In the present day, applications of cloud computing is growing exponentially and clients are inclined to use the cloud server to store sensitive data, which is indexed by important or related keyword(s) available in the data. Once the data is stored, the client supplies some keywords to the cloud server and requests the corresponding data. If the data is stored in plaintext form, data privacy will be violated. Thus the client encrypts the data along with the realted keywords, and then stores the ciphertext in the cloud server. Encryption of data maintains the confidentiality, but this makes keyword search difficult. To solve this issue, designated server based public key encryption with keyword search (dPEKS) scheme is used. In dPEKS scheme, to get the encrypted data, the client computes a trapdoor related to a relevant keyword, and sends it to the cloud server, which then gives the ciphertext to the client provided that the trapdoor is verified. Hence, the client gets the data from the ciphertext. However, an adversary will not get any information on the data or the keywords. A certificateless dPEKS (CL-dPEKS) scheme is proposed in this paper. It provides indistinguishability to the ciphertext and trapdoor, and resilience to off-line keyword guessing attack. The Computational Diffie-Hellman (CDH) problem and Bilinear Diffie-Hellman (BDH) problem keep the proposed scheme secure.
KeywordsCL-PKC dPEKS Bilinear pairing Cloud server Keyword guessing attack
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