Description
Aggregate message authentication codes, as introduced by Katz and Lindell (CT-RSA 2008), combine several MACs into a single value, which has roughly the same size as an ordinary MAC. These schemes reduce the communication overhead significantly and are therefore a promising approach to achieve authenticated communication in mobile ad-hoc networks, where communication is prohibitively expensive. Here we revisit the unforgeability notion for aggregate MACs and discuss that the definition does not prevent "mix-and-match" attacks in which the adversary turns several aggregates into a "fresh" combination, i.e., into a valid aggregate on a sequence of messages which the attacker has not requested before. In particular, we show concrete attacks on the previous scheme.<br/> To capture the broader class of combination attacks, we provide a stronger security notion of aggregation unforgeability. While we can provide stateful transformations lifting (non-ordered) schemes to meet our stronger security notion, for the statefree case we switch to the new notion of history-free se- quential aggregation. This notion is somewhat between non-ordered and se- quential schemes and basically says that the aggregation algorithm is carried out in a sequential order but must not depend on the preceding messages in the sequence, but only on the shorter input aggregate and the local message. We finally show that we can build an aggregation-unforgeable, history-free sequential MAC scheme based on general assumptions.
Prochains exposés
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TBA
Orateur : Eran Lambooij - Inria
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Cryptography
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Key Attack on the ACDGV Matrix Encryption Scheme
Orateur : Anmoal Porwal - Technical University of Munich
I will present our key-recovery attack on the ACDGV public-key encryption scheme proposed at ASIACRYPT 2024 by Aragon, Couvreur, Dyseryn, Gaborit, and Vinçotte. The secret key is a Gabidulin code hidden by appending random rows and columns and by left- and right-multiplication with invertible matrices. Our attack exploits the resulting algebraic structure to recover an equivalent secret key. It[…]-
Cryptography
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Asymmetric primitive
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Module Learning With Errors and Structured Extrapolated Dihedral Cosets
Orateur : Jinwei Zheng - Télécom Paris
The Module Learning With Errors (MLWE) problem is the fundamental hardness assumption underlying the key encapsulation and signature schemes ML-KEM and ML-DSA, which have been selected by NIST for post-quantum cryptography standardization. Understanding its quantum hardness is crucial for assessing the security of these standardized schemes. Inspired by the equivalence between LWE and[…]-
Cryptography
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