No abstract

No abstract

No abstract

Abstract. We present the first general MPC protocol that satisfies the following: (1) the construction is black-box, (2) the protocol is universally composable in the plain model, and (3) the number of rounds is constant. The security of our protocol is proven in angel-based UC security under the assumption of the existence of one-way functions that are secure against sub-exponential-time adversaries and constant-round semi-honest oblivious transfer protocols that are secure against quasi-polynomial-time adversaries. We obtain the MPC protocol by constructing a constant-round CCA-secure commitment scheme in a black-box way under the assumption of the existence of one-way functions that are secure against subexponential-time adversaries. To justify the use of such a sub-exponential hardness assumption in obtaining our constant-round CCA-secure commitment scheme, we show that if black-box reductions are used, there does not exist any constant-round CCA-secure commitment scheme under any falsifiable polynomial-time hardness assumptions.

No abstract

No abstract

No abstract

This paper proposes new card-based cryptographic protocols to calculate logic functions with the minimum number of cards using private operations under the semi-honest model. Though various card-based cryptographic protocols were shown, the minimum number of cards used in the protocol has not been achieved yet for many problems. Operations executed by a player where the other players cannot see are called private operations. Private operations have been introduced in some protocols to solve a particular problem or to input private values. However, the effectiveness of introducing private operations to the calculation of general logic functions has not been considered. This paper introduces three new private operations: private random bisection cuts, private reverse cuts, and private reveals. With these three new operations, we show that all of AND, XOR, and copy protocols are achieved with the minimum number of cards by simple three-round protocols. This paper then shows a protocol to calculate any logical functions using these private operations. Next, we consider protocols with malicious players.