A Computationally Secure Quantum Oblivious Transfer Scheme

Oblivious transfer is an important primitive in modern cryptography and is widely utilized in designing more complex protocols. In a one-out-of-two oblivious transfer, a party Alice has two messages x ₀, x₁ send to another party Bob in such a way that he can decide to obtain one of them at his choice but not both. In the literature (A. Kawachi et al., EUROCRYPT 2005, 268-284), the quantum states p_pi ⁺ and p_pi ^- are used as public keys to construct an encryption algorithm. In the paper, we further demonstrate that, for pi ne thetas, the quantum states p_pi ^plusmn and p_thetas ^plusmn can´t been distinguished by quantum computers. Using this result, we devise a one-out-of-two oblivious transfer scheme, in which any cheating of the entities are detected at the end of the protocol. Correctness and privacy of this protocol are analyzed and results show that the proposed scheme is computationally secured