Characterizing the qIND-qCPA (in)security of the CBC, CFB, OFB and CTR modes of operation

We fully characterize the post-quantum security of the $\mathsf{CBC}$, $\mathsf{CFB}$, $\mathsf{OFB}$ and $\mathsf{CTR}$ modes of operation by considering all possible notions of $\textsf{qIND-qCPA}$ security defined by Carstens, Ebrahimi, Tabia and Unruh (TCC 2021), thus extending the work performed by Anand, Targhi, Tabia and Unruh (PQCrypto 2016). We show that the results obtained by Anand et al. for the $\textsf{qIND-qCPA-P6}$ security of these modes carry on to the other $\textsf{IND-qCPA}$ notions, namely the $\textsf{qIND-qCPA-P10}$ and $\textsf{qIND-qCPA-P11}$ ones. We also show that all of these modes are insecure according to all of the other notions, regardless of the block cipher they are used with. We also provide two general results concerning the insecurity of commonly used properties of block ciphers, namely those preserving the length of their input and those using the $\texttt{XOR}$ operation as a way to randomize the encryption. Finally, we use these results to highlight the need for new quantum semantic security notions

Toward Lightweight Cryptography: A Survey

The main problem in Internet of Things (IoT) security is how to find lightweight cryptosystems that are suitable for devices with limited capabilities. In this paper, a comprehensive literature survey that discusses the most prominent encryption algorithms used in device security in general and IoT devices in specific has been conducted. Many studies related to this field have been discussed to identify the most technical requirements of lightweight encryption systems to be compatible with variances in IoT devices. Also, we explored the results of security and performance of the AES algorithm in an attempt to study the algorithm performance for keeping an acceptable security level which makes it more adaptable to IoT devices as a lightweight encryption system

Post-quantum security of hash functions

The research covered in this thesis is dedicated to provable post-quantum security of hash functions. Post-quantum security provides security guarantees against quantum attackers. We focus on analyzing the sponge construction, a cryptographic construction used in the standardized hash function SHA3. Our main results are proving a number of quantum security statements. These include standard-model security: collision-resistance and collapsingness, and more idealized notions such as indistinguishability and indifferentiability from a random oracle. All these results concern quantum security of the classical cryptosystems. From a more high-level perspective we find new applications and generalize several important proof techniques in post-quantum cryptography. We use the polynomial method to prove quantum indistinguishability of the sponge construction. We also develop a framework for quantum game-playing proofs, using the recently introduced techniques of compressed random oracles and the One-way-To-Hiding lemma. To establish the usefulness of the new framework we also prove a number of quantum indifferentiability results for other cryptographic constructions. On the way to these results, though, we address an open problem concerning quantum indifferentiability. Namely, we disprove a conjecture that forms the basis of a no-go theorem for a version of quantum indifferentiability

Algorithmes quantiques pour la cryptanalyse et cryptographie symétrique post-quantique

Modern cryptography relies on the notion of computational security. The level of security given by a cryptosystem is expressed as an amount of computational resources required to break it. The goal of cryptanalysis is to find attacks, that is, algorithms with lower complexities than the conjectural bounds.With the advent of quantum computing devices, these levels of security have to be updated to take a whole new notion of algorithms into account. At the same time, cryptography is becoming widely used in small devices (smart cards, sensors), with new cost constraints.In this thesis, we study the security of secret-key cryptosystems against quantum adversaries.We first build new quantum algorithms for k-list (k-XOR or k-SUM) problems, by composing exhaustive search procedures. Next, we present dedicated cryptanalysis results, starting with a new quantum cryptanalysis tool, the offline Simon's algorithm. We describe new attacks against the lightweight algorithms Spook and Gimli and we perform the first quantum security analysis of the standard cipher AES.Finally, we specify Saturnin, a family of lightweight cryptosystems oriented towards post-quantum security. Thanks to a very similar structure, its security relies largely on the analysis of AES.La cryptographie moderne est fondée sur la notion de sécurité computationnelle. Les niveaux de sécurité attendus des cryptosystèmes sont exprimés en nombre d'opérations ; une attaque est un algorithme d'une complexité inférieure à la borne attendue. Mais ces niveaux de sécurité doivent aujourd'hui prendre en compte une nouvelle notion d'algorithme : le paradigme du calcul quantique. Dans le même temps,la délégation grandissante du chiffrement à des puces RFID, objets connectés ou matériels embarqués pose de nouvelles contraintes de coût.Dans cette thèse, nous étudions la sécurité des cryptosystèmes à clé secrète face à un adversaire quantique.Nous introduisons tout d'abord de nouveaux algorithmes quantiques pour les problèmes génériques de k-listes (k-XOR ou k-SUM), construits en composant des procédures de recherche exhaustive.Nous présentons ensuite des résultats de cryptanalyse dédiée, en commençant par un nouvel outil de cryptanalyse quantique, l'algorithme de Simon hors-ligne. Nous décrivons de nouvelles attaques contre les algorithmes Spook et Gimli et nous effectuons la première étude de sécurité quantique du chiffrement AES. Dans un troisième temps, nous spécifions Saturnin, une famille de cryptosystèmes à bas coût orientés vers la sécurité post-quantique. La structure de Saturnin est proche de celle de l'AES et sa sécurité en tire largement parti