Description
Forward-secure signatures (FSS) prevent forgeries for past time periods when an attacker obtains full access to the signer's storage. To simplify the integration of these primitives into standard security architectures, Boyen, Shacham, Shen and Waters recently introduced the concept of forward-secure signatures with untrusted updates where private keys are additionally protected by a second factor (derived from a password). Key updates can be made on encrypted version of signing keys so that passwords only come into play for signing messages.<br/> The scheme put forth by Boyen et al. relies on bilinear maps and does not require the random oracle. The latter work also suggested the integration of untrusted updates in the Bellare-Miner forward-secure signature and left open the problem of endowing other existing FSS systems with the same second factor protection. We solve this problem by showing how to adapt the very efficient generic construction of Malkin, Micciancio and Miner (MMM) to untrusted update environments. More precisely, our modified construction - which does not use random oracles either - obtains a forward-secure signature with untrusted updates from any 2-party multi-signature in the plain public key model. In combination with Bellare and Neven's multi-signatures, our generic method yields implementations based on standard assumptions such as RSA, factoring or the hardness of computing discrete logarithms. Like the original MMM scheme, it does not require to set a bound on the number of time periods at key generation.
Prochains exposés
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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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