Computational Oblivious Transfer and Interactive Hashing

We use interactive hashing to achieve the most efficient OT protocol to date based solely on the assumption that trapdoor permutations (TDP) exist. Our protocol can be seen as the following (simple) modification of either of the two famous OT constructions: 1) In the one by Even et al (1985), a receiver must send a random domain element to a sender through IH; 2) In the one by Ostrovsky et al (1993), the players should use TDP instead of one-way permutation. A similar approach is employed to achieve oblivious transfer based on the security of the McEliece cryptosystem. In this second protocol, the receiver inputs a public key into IH, while privately keeping the corresponding secret key. Two different versions of IH are used: the computationally secure one in the first protocol, and the informationtheoretically secure one in the second.