An oblivious transfer protocol with log-squared communication

Abstract

We propose a one-round 1-out-of-n computationally-private information retrieval protocol for ℓ-bit strings with low-degree polylogarithmic receiver-computation, linear sender-computation and communication ⊖(k · log2 n + ℓ - logn), where k is a possibly non-constant security parameter. The new protocol is receiver-private if the underlying length-flexible additively homomorphic public-key cryptosystem is IND-CPA secure. It can be transformed to a one-round computationally receiver-private and information-theoretically sender-private 1-out-of-n oblivious-transfer protocol for ℓ-bit strings, that has the same asymptotic communication and is private in the standard complexity-theoretic model. © Springer-Verlag Berlin Heidelberg 2005.