Optimal Reductions Between Oblivious Transfers Using Interactive Hashing

Abstract. We present an asymptotically optimal reduction of one-outof-two String Oblivious Transfer to one-out-of-two Bit Oblivious Transfer using Interactive Hashing in conjunction with Privacy Amplification. Interactive Hashing is used as in an innovative way to test the receiver's adherence to the protocol. We show that (1 + )k uses of Bit OT suffice to implement String OT for k-bit strings. Our protocol represents a two-fold improvement over the best constructions in the literature and is asymptotically optimal. We then show that our construction can also accommodate weaker versions of Bit OT obtaining in all three cases a significantly lower expansion factor compared to previous constructions. Besides increasing efficiency, our constructions impose no constraints on the 2-universal families of Hash Functions used for Privacy Amplification. Of independent interest, our reduction illustrates the power of Interactive Hashing as an ingredient in the design of cryptographic protoc...

• Type: Conference
• Year: 2006
• Where: EUROCRYPT
• Authors: Claude Crépeau, George Savvides
• Keywords: Bit OT, Cryptology, EUROCRYPT 2006, Interactive Hashing, Oblivious Transfer