Cryptology ePrint Archive: Report 2022/382

Witness-Authenticated Key Exchange Revisited: Improved Models, Simpler Constructions, Extensions to Groups

Matteo Campanelli and Rosario Gennaro and Kelsey Melissaris and Luca Nizzardo

Abstract: We revisit the notion of Witness Authenticated Key Exchange ($\mathsf{WAKE}$) where a party can be authenticated through a generic witness to an $\mathsf{NP}$ statement. We point out shortcomings of previous definitions, protocols and security proofs in Ngo et al. (Financial Cryptography 2021) for the (unilaterally-authenticated) two-party case. In order to overcome these limitations we introduce new models and protocols, including the first definition in literature of group witness-authenticated key exchange. We provide simple constructions based on (succinct) signatures of knowledge. Finally, we discuss their concrete performance for several practical applications in highly decentralized networks.

Category / Keywords: cryptographic protocols / key agreement, signatures of knowledge, witness encryption

Date: received 23 Mar 2022, last revised 23 Mar 2022

Contact author: matteo at protocol ai, kelseymelissaris at gmail com, luca nizzardo at protocol ai, rosario gennaro at protocol ai

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Version: 20220328:143423 (All versions of this report)

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