New Techniques for Private Stream Searching

Abstract

A system for private stream searching, introduced by Ostrovsky and Skeith, allows a client to provide an untrusted server with an encrypted search query. The server uses the query on a stream of documents and returns the matching documents to the client while learning nothing about the nature of the query. We present a new scheme for conducting private keyword search on streaming data which requires O ( m ) server to client communication complexity to return the content of the matching documents, where m is an upper bound on the size of the documents. The required storage on the server conducting the search is also O ( m ). The previous best scheme for private stream searching was shown to have O ( m log m ) communication and storage complexity. Our solution employs a novel construction in which the user reconstructs the matching files by solving a system of linear equations. This allows the matching documents to be stored in a compact buffer rather than relying on redundancies to avoid collisions in the storage buffer as in previous work. This technique requires a small amount of metadata to be returned in addition to the documents; for this the original scheme of Ostrovsky and Skeith may be employed with O ( m log m ) communication and storage complexity. We also present an alternative method for returning the necessary metadata based on a unique encrypted Bloom filter construction. This method requires O ( m log( t / m )) communication and storage complexity, where t is the number of documents in the stream. In this article we describe our scheme, prove it secure, analyze its asymptotic performance, and describe a number of extensions. We also provide an experimental analysis of its scalability in practice. Specifically, we consider its performance in the demanding scenario of providing a privacy preserving version of the Google News Alerts service.

Function-Private Identity-Based Encryption: Hiding the Function in Functional Encryption

“…Constructions in these settings support efficient equality testing [OS07,BSW09] and can be viewed as a more expressive variant of private information retrieval.…”

Address Permutation for Privacy-Preserving Searchable Symmetric Encryption

“…The scheme in [15] has a somewhat different setting from the proposed scheme, in the sense that servers can access the data while the search keywords are hidden from the servers. In the proposed scheme, both the search keywords and data are regarded as sensitive information, and therefore they are encrypted.…”

“…In the proposed scheme, both the search keywords and data are regarded as sensitive information, and therefore they are encrypted. Also, [15] is based on Paillier's homomorphic cryptosystem in [16]. This is a public key cryptosystem, and therefore it takes more resources than a symmetric cryptosystem.…”

Performances of cryptographic accumulators

“…Many applications have been found ranging from time-stamping schemes [20], search on encrypted data [4,13] to data aggregation in sensor networks [19] and distillation codes [16] among others. For instance, Sander et al [26] use RSA accumulator to design blind and auditable membership proof scheme in the context of e-cash.…”