A More Efficient Card-Based Protocol for Generating a Random Permutation without Fixed Points

Many works have been done for secure computation of functions. Most of them assume computation on computers. The protocols are difficult for the people who has no knowledge on cryptography. Therefore, secure computation using cards was considered. Since nothing other than the cards are used, the protocols are easy to understand for the people who has no knowledge on cryptography. This paper presents a card-based protocol that generates a random hidden permutation. This problem is applicable to a case when players exchange gifts. The protocol must not output a permutation with a fixed point, which means that every player does not receive the gift he/she prepared. Ishikawa et. al proposed a protocol with two-color cards using random shuffles and a proof of having no fixed points. However, the success probability of the protocol is not so high. Therefore, more efficient random permutation protocol is required. In this paper, we use cyclic shuffles in addition to the random shuffles to lower the possibility of fixed points. We show the success probability of obtaining a permutation without fixed points by our protocol is better than the one by the existing protocol.