Effective Oblivious Transfer Using a Probabilistic Encryption

Abstract

Some novel effective 1-out-of-2, 1-out-of-n, n−1-out-of-n, andm-out-of-n interactive and non-interactive oblivious transfer protocols (OT protocols) using a probabilistic encryption are presented. Their key information is adapted from corresponding Bellare − Rivest fractional OT protocols and the encryption is carried out on ElGamal. They can be realized in a multiplicative as well as an additive group of prime order. It is shown that due to usage of different encryption keys this implementation can be simplified in such a way that single randomizer is sufficient for all encryptions. The proposal allows to increase the information rate by 2n/(n+1) times and to reduce by the same factor the computational complexity of the second round phase of interactive and of the communication phase of non-interactive m-out-of-n OT protocols explored probabilistic encryption. These propositions have potential applications in all cryptographic protocols based on the m-out-of-n oblivious transfer using probabilistic encryption including generalized oblivious transfer, in particular in electronic commerce.