International Association for Cryptologic Research

International Association
for Cryptologic Research


Tightly-Secure Authenticated Key Exchange, Revisited

Tibor Jager , Bergische Universität Wuppertal
Eike Kiltz , Ruhr-Universität Bochum
Doreen Riepel , Ruhr-Universität Bochum
Sven Schäge , Ruhr-Universität Bochum
DOI: 10.1007/978-3-030-77870-5_5 (login may be required)
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Presentation: Slides
Conference: EUROCRYPT 2021
Abstract: We introduce new tightly-secure authenticated key exchange (AKE) protocols that are extremely efficient, yet have only a constant security loss and can be instantiated in the random oracle model both from the standard DDH assumption and a subgroup assumption over RSA groups. These protocols can be deployed with optimal parameters, independent of the number of users or sessions, without the need to compensate a security loss with increased parameters and thus decreased computational efficiency. We use the standard “Single-Bit-Guess” AKE security (with forward secrecy and state corruption) requiring all challenge keys to be simultaneously pseudo-random. In contrast, most previous papers on tightly secure AKE protocols (Bader et al., TCC 2015; Gjøsteen and Jager, CRYPTO 2018; Liu et al., ASIACRYPT 2020) concentrated on a non-standard “Multi-Bit-Guess” AKE security which is known not to compose tightly with symmetric primitives to build a secure communication channel. Our key technical contribution is a new generic approach to construct tightly-secure AKE protocols based on non-committing key encapsulation mechanisms. The resulting DDH-based protocols are considerably more efficient than all previous constructions.
Video from EUROCRYPT 2021
  title={Tightly-Secure Authenticated Key Exchange, Revisited},
  author={Tibor Jager and Eike Kiltz and Doreen Riepel and Sven Schäge},