Privacy preserving keyword searches on remote encrypted data

Abstract

We consider the following problem: a user μ wants to store his files in an encrypted form on a remote file server S. Later the user μ wants to efficiently retrieve some of the encrypted files containing (or indexed by) specific keywords, keeping the keywords themselves secret and not jeopardizing the security of the remotely stored files. For example, a user may want to store old e-mail messages encrypted on a server managed by Yahoo or another large vendor, and later retrieve certain messages while travelling with a mobile device. In this paper, we offer solutions for this problem under well-defined security requirements. Our schemes are efficient in the sense that no public-key cryptosystem is involved. Indeed, our approach is independent of the encryption method chosen for the remote files. They are also incremental, in that μ can submit new files which are secure against previous queries but still searchable against future queries. © Springer-Verlag Berlin Heidelberg 2005.