Cryptology ePrint Archive: Report 2021/1357

Two-Round Concurrently Secure Two-Party Computation

Behzad Abdolmaleki and Giulio Malavolta and Ahmadreza Rahimi

Abstract: In this paper, we study the round complexity of concurrently secure computation protocols in the plain model, without random oracles or assuming the presence of a trusted setup. In the plain model, it is well known that concurrently secure two-party computation with polynomial simulation is impossible to achieve in two rounds. For this reason, we focus on the well-studied notion of security with super-polynomial simulation (SPS). Our main result is the first construction of two-round SPS two-party computation for general functionalities in the plain model. Prior to our work, we only knew three-round constructions [Badrinarayanan et al., TCC 2017] and two-round protocols were not known from any computational assumption. As immediate applications, we establish the feasibility result for a series of cryptographic primitives of interest, such as: Two-round password authentication key exchange (PAKE) in the plain model, two-round concurrent blind signature in the plain model, and two round concurrent computation for quantum circuits (2PQC).

Category / Keywords: cryptographic protocols / Two-party computations quantum two-party computation, concurrent blind signature, concurrent PAKE, 2PQC

Date: received 8 Oct 2021

Contact author: behzad abdolmaleki at csp mpg de, giulio malavolta at csp mpg de, ahmadreza rahimi at csp mpg de

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Version: 20211012:061333 (All versions of this report)

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