Efficient 1-Out-2 Oblivious Transfer Schemes Based on EDDH Assumption

This paper proposes an efficient 1-out-2 oblivious transfer scheme from fundamental cryptographic techniques directly. It achieves optimal efficiency in terms of the number of rounds and the total number of exchanged messages for the case that the receiver´s choice is unconditionally secure. The computation time of the 1-out-2 oblivious transfer scheme is very efficient, too. The receiver need compute 4 modular exponentiations only, and the sender need compute 8 modular exponentiations. The new construction is secure if the EDDH assumption holds. Since EDDH assumption is weaker than DDH assumption for generic bilinear groups, the new scheme is a good replacement for Wen-Guey Tzeng´s oblivious transfer schemes when bilinear group is adopted as construction platform.