Attack on LAC Key Exchange in Misuse Situation - Inria - Institut national de recherche en sciences et technologies du numérique Accéder directement au contenu
Communication Dans Un Congrès Année : 2020

Attack on LAC Key Exchange in Misuse Situation

Résumé

LAC is a Ring Learning With Error based cryptosystem that has been proposed to the NIST call for post-quantum standardization and passed the rst round of the submission process. The particularity of LAC is to use an error-correction code ensuring a high security level with small key sizes and small ciphertext sizes. LAC team proposes a CPA secure cryptosystem, LAC.CPA, and a CCA secure one, LAC.CCA, obtained by applying the Fujisaki-Okamoto transformation on LAC.CPA. In this paper, we study the security of LAC Key Exchange (KE) mechanism, using LAC.CPA, in a misuse context: when the same secret key is reused for several key exchanges and an active adversary has access to a mismatch oracle. This oracle indicates information on the possible mismatch at the end of the KE protocol. In this context, we show that an attacker needs at most 8 queries to the oracle to retrieve one coecient of a static secret key. This result has been experimentally conrmed using the reference and optimized implementations of LAC. Since our attack can break the CPA version in a misuse context, the Authenticated KE protocol, based on the CCA version, is not impacted. However, this research provides a tight estimation of LAC resilience against this type of attacks.
Fichier principal
Vignette du fichier
misuseAttackLAC.pdf (472.11 Ko) Télécharger le fichier
Origine Fichiers produits par l'(les) auteur(s)

Dates et versions

hal-03046345 , version 1 (08-12-2020)

Identifiants

  • HAL Id : hal-03046345 , version 1

Citer

Aurélien Greuet, Simon Montoya, Guénaël Renault. Attack on LAC Key Exchange in Misuse Situation. CANS 2020 - 19th International conference on Cryptology and Network Security, Dec 2020, Vienna, Austria. ⟨hal-03046345⟩
81 Consultations
228 Téléchargements

Partager

Gmail Mastodon Facebook X LinkedIn More