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IACR Communications in Cryptology
Article . 2025 . Peer-reviewed
License: CC BY
Data sources: Crossref
DBLP
Article . 2025
Data sources: DBLP
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Round-Optimal Authenticated Key Exchange with Full Forward Privacy

Authors: Koki Matsui; Shoma Kanzaki; Wakaha Ogata; Keitaro Hashimoto;

Round-Optimal Authenticated Key Exchange with Full Forward Privacy

Abstract

Privacy-preserving authenticated key exchange (PPAKE) is a cryptographic protocol that enables two users to exchange a session key while protecting users' privacy (i.e., hiding the user's identity) against the machine-in-the-middle adversary. To hide user identities, PPAKE messages are broadcast to the network, increasing communication complexity. In ASIACRYPT2022, Lyu et al. introduced a concept of robustness to reduce communication complexity. Roughly, robust PPAKE allows receivers to decide whether it is the intended user by processing the first message with its long-term secret key. As a result, only the intended user replies to the first message, and thus, messages in the network are reduced. However, if a user's secret key is leaked, an adversary can also use it to determine whether the past first message was intended for the user, and thus, the PPAKE scheme of Lyu et al. does not have full forward privacy. Lyu et al. leave an open problem of constructing a PPAKE scheme with robustness and full forward privacy. In this work, we solve this problem by introducing a new framework called key updatable PPAKE (kuPPAKE). In kuPPAKE schemes, a long-term secret key is updated so that the updated key does not work for past messages. Therefore, robustness no longer conflicts with full forward privacy. We propose a generic construction of a 2-round kuPPAKE and show a concrete scheme in the standard model from DH-style assumptions over bilinear groups.

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selected citations
These citations are derived from selected sources.
This is an alternative to the "Influence" indicator, which also reflects the overall/total impact of an article in the research community at large, based on the underlying citation network (diachronically).
BIP!Citations provided by BIP!
popularity
This indicator reflects the "current" impact/attention (the "hype") of an article in the research community at large, based on the underlying citation network.
BIP!Popularity provided by BIP!
influence
This indicator reflects the overall/total impact of an article in the research community at large, based on the underlying citation network (diachronically).
BIP!Influence provided by BIP!
impulse
This indicator reflects the initial momentum of an article directly after its publication, based on the underlying citation network.
BIP!Impulse provided by BIP!
0
Average
Average
Average
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