abstractXOR: A global constraint dedicated to differential cryptanalysis

International audienceConstraint Programming models have been recently proposed to solve cryptanalysis problems for symmetric block ciphers such as AES. These models are more efficient than dedicated approaches but their design is difficult: straightforward models do not scale well and it is necessary to add advanced constraints derived from cryptographic properties. We introduce a global constraint which simplifies the modelling step and improves efficiency. We study its complexity, introduce propagators and experimentally evaluate them on two cryptanalysis problems (single-key and related-key) for two block ciphers (AES and Midori)

Mind the Gap - A Closer Look at the Security of Block Ciphers against Differential Cryptanalysis

Resistance against differential cryptanalysis is an important design criteria for any modern block cipher and most designs rely on finding some upper bound on probability of single differential characteristics. However, already at EUROCRYPT'91, Lai et al. comprehended that differential cryptanalysis rather uses differentials instead of single characteristics. In this paper, we consider exactly the gap between these two approaches and investigate this gap in the context of recent lightweight cryptographic primitives. This shows that for many recent designs like Midori, Skinny or Sparx one has to be careful as bounds from counting the number of active S-boxes only give an inaccurate evaluation of the best differential distinguishers. For several designs we found new differential distinguishers and show how this gap evolves. We found an 8-round differential distinguisher for Skinny-64 with a probability of 2−56.932−56.93, while the best single characteristic only suggests a probability of 2−722−72. Our approach is integrated into publicly available tools and can easily be used when developing new cryptographic primitives. Moreover, as differential cryptanalysis is critically dependent on the distribution over the keys for the probability of differentials, we provide experiments for some of these new differentials found, in order to confirm that our estimates for the probability are correct. While for Skinny-64 the distribution over the keys follows a Poisson distribution, as one would expect, we noticed that Speck-64 follows a bimodal distribution, and the distribution of Midori-64 suggests a large class of weak keys

Synthesis and Crystal Structures of Cd(OH)Cl and Cu(OH)Cl and Relationship to Brucite Type

International audienceSynthesis of single crystals of Cd(OH)Cl and Cu(OH)Cl allowed to revisit the structure of these hydroxychlorides and confirm their space group: P63mc ( R = 0.041; Rw = 0.050 ) for Cd(OH)Cl and P21/c ( R = 0.051; Rw = 0.072 ) for Cu(OH)Cl. Positions of hydrogen atoms were determined and an hypothesis of hydrogen bonds is discussed in relation with the infrared spectra. A comparison of the structures shows that an isomorphism is not possible between the two compounds, due to the important Jahn-Teller effect of divalent copper. On the other hand, a structural relationship exists between Cd(OH)Cl and beta-Cd(OH)2 which belongs to the brucite type family

Synthesis and study of Cu(NO 2 ) 2 (NH 3 ) 4 and Cu(NO 2 ) 2 (NH 3 ) 2

International audienceCrystals of Cu(NO2)2(NH3)4 and Cu(NO2)2(NH3)2 have been prepared and studied. Two allotropic species exist for each compound, alpha-Cu(NO2)2(NH3)4 is orthorhombic, space group Fmmm or Fmm2; a(Ǻ) = 20.671(15), b(Ǻ) = 6.796(5), c(Ǻ) = 11.414(8), Z = 8; beta-Cu(NO2)2(NH3)4 is orthorhombic, space group Cccm or Ccc2; a(Ǻ) = 10.467(7), b(Ǻ) = 17.766(9), c(Ǻ) = 13.700(9), Z = 12; alpha-Cu(NO2)2(NH3)2 is triclinic, space group P-1, a(Ǻ) = 4.4165(12), b(Ǻ) = 5.6104(14), c(Ǻ) = 6.088(2), alpha° = 78.45(3), beta° = 103.95(3), gamma° = 100.16(3),Z = 1; beta-Cu(NO2)2(NH3)2 is monoclinic space group Cm or C2; a(Ǻ) = 9.226(6), b(Ǻ) = 7.556(3), c(Ǻ) = 4.486(3), beta° = 104.84(6), Z=2

Synthesis and study of Cu(NO 2 ) 2 (NH 3 ) 4 and Cu(NO 2 ) 2 (NH 3 ) 2

International audienceCrystals of Cu(NO2)2(NH3)4 and Cu(NO2)2(NH3)2 have been prepared and studied. Two allotropic species exist for each compound, alpha-Cu(NO2)2(NH3)4 is orthorhombic, space group Fmmm or Fmm2; a(Ǻ) = 20.671(15), b(Ǻ) = 6.796(5), c(Ǻ) = 11.414(8), Z = 8; beta-Cu(NO2)2(NH3)4 is orthorhombic, space group Cccm or Ccc2; a(Ǻ) = 10.467(7), b(Ǻ) = 17.766(9), c(Ǻ) = 13.700(9), Z = 12; alpha-Cu(NO2)2(NH3)2 is triclinic, space group P-1, a(Ǻ) = 4.4165(12), b(Ǻ) = 5.6104(14), c(Ǻ) = 6.088(2), alpha° = 78.45(3), beta° = 103.95(3), gamma° = 100.16(3),Z = 1; beta-Cu(NO2)2(NH3)2 is monoclinic space group Cm or C2; a(Ǻ) = 9.226(6), b(Ǻ) = 7.556(3), c(Ǻ) = 4.486(3), beta° = 104.84(6), Z=2

Synthesis, Crystal Structure and Porosity Estimation of Hydrated Erbium Terephtalate Coordination Polymers

International audienc

Comportement de la Xonotlite Exposée aux Hautes Températures

National audienc

Comportement de la xonotlite exposée aux hautes températures

Afin de modéliser le comportement thermomécanique de matériaux dédiés à la protection incendie, l'étude de leur comportement thermophysique est mise en œuvre. Le produit composite étudié est essentiellement composé de xonotlite, un silicate de calcium hydraté renforcé par des fibres organiques de type cellulose. Différentes méthodes d'analyses sont utilisées pour suivre l'évolution de la structure du produit soumis à un incendie (T$\,{>}\,$1000$^{\circ}$C et présence de flammes) : mesures ATD/TG, diffraction des rayons X (température ambiante ou thermodiffraction). Les résultats de ces analyses sont croisés avec des visualisations MEB. L'analyse de l'évolution des phases cristallines associée à une évolution importante et rapide de température permet de comprendre comment le matériau supporte l'incendie. L'identification de ses conditions de ruine du produit découle de cette étude