Rafail Ostrovsky - Publications

One-way Trapdoor Permutations Are Sufficient for Non-Trivial Single-Server Private Information Retrieval

Eyal Kushilevitz, Rafail Ostrovsky


We show that general one-way trapdoor permutations are sufficient to privately retrieve an entry from a database of size n with total communication complexity strictly less than n. More specifically, we present a protocol in which the user sends O(K2) bits and the server sends n-cn K bits (for any constant c), where K is the security parameter of the trapdoor permutations. Thus, for sufficiently large databases (e.g., when K=n for some small ∈ our construction breaks the information-theoretic lower-bound (of at least n bits). This demonstrates the feasibility of basing single-server private information retrieval on general complexity assumptions.

An important implication of our result is that we can implement a 1-out-of-n Oblivious Transfer protocol with communication complexity strictly less than n based on any one-way trapdoor permutation.

comment: Appeared In Proceedings of Advances in Cryptology B. Prneel (ED.): EUROCRYPT 2000, LNCS 1807, pp. 104-121, 2000. Springer-Verlag.

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