[Resource Topic] 2020/320: Universally Composable Relaxed Password Authenticated Key Exchange

Welcome to the resource topic for 2020/320

Title:
Universally Composable Relaxed Password Authenticated Key Exchange

Authors: Michel Abdalla, Manuel Barbosa, Tatiana Bradley, Stanislaw Jarecki, Jonathan Katz, Jiayu Xu

Abstract:

Protocols for password authenticated key exchange (PAKE) allow two parties who share only a weak password to agree on a cryptographically strong key. We revisit the notion of PAKE in the framework of universal composability, and propose a relaxation of the PAKE functionality of Canetti et al. that we call lazy-extraction PAKE (lePAKE). Roughly, our relaxation allows the ideal-world adversary to postpone its password guess even until after a session is complete. We argue that this relaxed notion still provides meaningful security in the password-only setting. As our main result, we show that several PAKE protocols that were previously only proven secure with respect to a “game-based” definition can in fact be shown to realize the lePAKE functionality in the random-oracle model. These include SPEKE, SPAKE2, and TBPEKE, the most efficient PAKE schemes currently known.

ePrint: https://eprint.iacr.org/2020/320

Talk: https://www.youtube.com/watch?v=aYuUN5XXzLk

Slides: https://iacr.org/submit/files/slides/2020/crypto/crypto2020/357/slides.pptx

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