09031 Abstracts Collection -- Symmetric Cryptography

From 11.01.09 to 16.01.09, the Seminar 09031 in ``Symmetric Cryptography \u27\u27 was held in Schloss Dagstuhl~--~Leibniz Center for Informatics. During the seminar, several participants presented their current research, and ongoing work and open problems were discussed. Abstracts of the presentations given during the seminar as well as abstracts of seminar results and ideas are put together in this paper. The first section describes the seminar topics and goals in general. Links to extended abstracts or full papers are provided, if available

07021 Abstracts Collection -- Symmetric Cryptography

From .. to .., the Dagstuhl Seminar 07021 ``Symmetric Cryptography\u27\u27 automatically was held in the International Conference and Research Center (IBFI), Schloss Dagstuhl. During the seminar, several participants presented their current research, and ongoing work and open problems were discussed. Abstracts of the presentations given during the seminar as well as abstracts of seminar results and ideas are put together in this paper. The first section describes the seminar topics and goals in general. Links to extended abstracts or full papers are provided, if available

Towards a Theory of Symmetric Encryption

Motivée par le commerce et l'industrie, la recherche publique dans le domaine du chiffrement symétrique s'est considérablement développée depuis vingt cinq ans si bien qu'il est maintenant possible d'en faire le bilan. La recherche a tout d'abord progressé de manière empirique. De nombreux algorithmes de chiffrement fondés sur la notion de réseau de substitutions et de permutations ont été proposés, suivis d'attaques dédiées contre eux. Cela a permis de définir des stratégies générales: les méthodes d'attaques différentielles, linéaires et statistiques, et les méthodes génériques fondées sur la notion de boîte noire. En modélisant ces attaques on a trouvé en retour des règles utiles dans la conception d'algorithmes sûrs: la notion combinatoire de multipermutation pour les fonctions élémentaires, le contrôle de la diffusion par des critères géométriques de réseau de calcul, l'étude algébrique de la non-linéarité, ... Enfin, on montre que la sécurité face à un grand nombre de classes d'attaques classiques est assurée grâce à la notion de décorrélation par une preuve formelle. Ces principes sont à l'origine de deux algorithmes particuliers: la fonction CS-Cipher qui permet un chiffrement à haut débit et une sécurité heuristique, et le candidat DFC au processus de standardisation AES, prototype d'algorithme fondé sur la notion de décorrélation

Optimising Linear Key Recovery Attacks with Affine Walsh Transform Pruning

International audienceLinear cryptanalysis [25] is one of the main families of keybrecovery attacks on block ciphers. Several publications [16,19] have drawn attention towards the possibility of reducing their time complexity using the fast Walsh transform. These previous contributions ignore the structure of the key recovery rounds, which are treated as arbitrary boolean functions. In this paper, we optimise the time and memory complexities of these algorithms by exploiting zeroes in the Walsh spectra of these functions using a novel affine pruning technique for the Walsh Transform. These new optimisation strategies are then showcased with two application examples: an improved attack on the DES [1] and the first known atttack on 29-round PRESENT-128 [9]

Distinguishing attacks on block ciphers by differentials of two-block texts

Предложена модель наблюдений (случайные двублочные тексты, шифруемые на независимых случайных ключах), в которой разностные атаки различения полностью соответствуют общепринятым схемам их статистического расчёта. В этой модели получены нижние границы и асимптотические оценки объёма материала мультиразностных атак различения. Показано, что материала объёма O (1/pmax ) недостаточно для успешной атаки при малых значениях pmax — максимальной вероятности перехода разностей. Проведены вычислительные и статистические эксперименты для марковских моделей шифрсистемы SmallPresent c длиной блока до 28 бит

A Review of Existing 4-bit Crypto S-box cryptanalysis Techniques and Two New Techniques with 4-bit Boolean Functions for Cryptanalysis of 4-bit Crypto S-boxes.

4-bit Linear Relations play an important role in Cryptanalysis of 4-bit Bijective Crypto S-boxes. 4-bit finite differences also a major part of cryptanalysis of 4-bit substitution boxes. Count of existence of all 4-bit linear relations, for all of 16 input and 16 output 4-bit bit patterns of 4-bit bijective crypto S-boxes said as S-boxes has been reported in Linear Cryptanalysis of 4-bit S-boxes. Count of existing finite differences from each element of output S-boxes to distant output S-boxes have been noted in Differential Cryptanalysis of S-boxes. In this paper a brief review of these cryptanalytic methods for 4-bit S-boxes has been introduced in a very lucid and conceptual manner. Two new Analysis Techniques, one to search for the existing Linear Approximations among the input Boolean Functions (BFs) and output BFs of a particular 4-bit S-Box has also been introduced in this paper. The search is limited to find the existing linear relations or approximations in the contrary to count the number existent linear relations among all 16 4-bit input and output bit patterns within all possible linear approximations. Another is to find number of balanced 4-bit BFs in difference output S-boxes. Better the number of Balanced BFs, Better the security