Efficient Conjunctive Keywords Search over Encrypted E-Mail Data in Public Key Setting

Searchable public key encryption supporting conjunctive keywords search (SPE-CKS) enables data users to retrieve the encrypted data of interest from an untrusted server. Based on SPE-CKS, one can realize a multi-keywords search over the encrypted e-mails. In this paper, we propose an efficient SPE-CKS scheme by utilizing a keyword conversion method and the bilinear map technique. Our scheme is proven to be secure against chosen keyword attack under a standard security definition and can also withstand the keywords guessing attack. Furthermore, we design an experiment over a real world e-mail dataset to illustrate that our scheme has a better performance on time and space complexities than the previous schemes. A detailed analysis shows that our scheme is very practical for the encrypted e-mail system in the mobile cloud environment.