Secure quantum private information retrieval using phase-encoded queries

Abstract

We propose a quantum solution to the classical private information retrieval (PIR) problem, which allows one to query a database in a private manner. The protocol offers privacy thresholds and allows the user to obtain information from a database in a way that offers the potential adversary, in this model the database owner, no possibility of deterministically establishing the query contents. This protocol may also be viewed as a solution to the symmetrically private information retrieval problem in that it can offer database security (inability for a querying user to steal its contents). Compared to classical solutions, the protocol offers substantial improvement in terms of communication complexity. In comparison with the recent quantum private queries [Phys. Rev. Lett. 100, 230502 (2008)] protocol, it is more efficient in terms of communication complexity and the number of rounds, while offering a clear privacy parameter. We discuss the security of the protocol and analyze its strengths and conclude that using this technique makes it challenging to obtain the unconditional (in the information-theoretic sense) privacy degree; nevertheless, in addition to being simple, the protocol still offers a privacy level. The oracle used in the protocol is inspired both by the classical computational PIR solutions as well as the Deutsch-Jozsa oracle.

Comment on “Secure quantum private information retrieval using phase-encoded queries”

“…The correctness proof of our improved QPQ protocol is same as that of the original phase-encoded QPQ protocol [4]. So we mainly focus on the security of our improved QPQ protocol in the following section.…”

“…[4], the author pointed out that, if a dishonest Bob performs an intercept-and-resend attack, he might eventually succeed but not with more than a 50% chance. However, the author did not consider more attacks performed by Bob.…”

“…Here, we simply review the original phase-encoded QPQ presented by Olejnik [4]. Suppose that Bob privately owns an N-element database: d(i) for i = 0 to N − 1, where d(i) ∈ {0,1} and Alice wants to obtain the ith element of the database.…”

“…However, in current phase-encoded QPQ protocols [4][5][6] as long as the returned system is in state…”

“…Compared to the classical related protocols, their quantum private query (QPQ) protocol achieves an exponential reduction both in communication complexity and in computational complexity. In 2011, Olejnik further proposed a phase-encoded QPQ protocol [4]. In comparison with the original QPQ protocol [3], the phase-encoded QPQ protocol displays two prominent advantages: lower communication cost and better implementability.…”