Cryptology ePrint Archive: Report 2020/035

Constant-round Dynamic Group Key Exchange from RLWE Assumption

Rakyong Choi and Dongyeon Hong and Kwangjo Kim

Abstract: In this paper, we propose a novel lattice-based group key exchange protocol with dynamic membership. Our protocol is constructed by generalizing Dutta-Barua protocol to RLWE setting, inspired by Apon et al.ís recent paper in PQCrypto 2019. We describe our (static) group key exchange protocol from Apon et al.ís paper by modifying its third round and computation step. Then, we present both authenticated and dynamic group key exchange protocol with Join and Leave algorithms. The number of rounds for authenticated group key exchange remains the same as unauthenticated one. Our protocol also supports the scalable property so that the number of rounds does not change depending on the number of group participants. By assuming the hardness of RLWE assumption and unforgeability of digital signatures, we give a full security proof for (un-)authenticated (dynamic) group key exchange protocols.

Category / Keywords: public-key cryptography / Dynamic group key exchange, authenticated key exchange, RLWE, constant-round group key exchange

Date: received 12 Jan 2020

Contact author: thepride at kaist ac kr

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Version: 20200113:103107 (All versions of this report)

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