Impossible Boomerang Attack for Block Cipher Structures

Impossible boomerang attack \cite{lu} (IBA) is a new variant of differential cryptanalysis against block ciphers. Evident from its name, it combines the ideas of both impossible differential cryptanalysis and boomerang attack. Though such an attack might not be the best attack available, its complexity is still less than that of the exhaustive search. In impossible boomerang attack, impossible boomerang distinguishers are used to retrieve some of the subkeys. Thus the security of a block cipher against IBA can be evaluated by impossible boomerang distinguishers. In this paper, we study the impossible boomerang distinguishers for block cipher structures whose round functions are bijective. Inspired by the $\mathcal{U}$-method in \cite{kim}, we provide an algorithm to compute the maximum length of impossible boomerang distinguishers for general block cipher structures, and apply the algorithm to known block cipher structures such as Nyberg\u27s generalized Feistel network, a generalized CAST256-like structure, a generalized MARS-like structure, a generalized RC6-like structure, etc

Parallelizing the Camellia and SMS4 Block Ciphers - Extended version

The n-cell GF-NLFSR (Generalized Feistel-NonLinear Feedback Shift Register) structure [8] is a generalized unbalanced Feistel network that can be considered as a generalization of the outer function FO of the KASUMI block cipher. An advantage of this cipher over other n-cell generalized Feistel networks, e.g. SMS4 [11] and Camellia [5], is that it is parallelizable for up to n rounds. In hardware implementations, the benefits translate to speeding up encryption by up to n times while consuming similar area and significantly less power. At the same time n-cell GF-NLFSR structures offer similar proofs of security against differential cryptanalysis as conventional n-cell Feistel structures. We also ensure that parallelized versions of Camellia and SMS4 are resistant against other block cipher attacks such as linear, boomerang, integral, impossible differential, higher order differential,interpolation, slide, XSL and related-key differential attacks

Cryptographic Properties and Application of a Generalized Unbalanced Feistel Network Structure (Revised Version)

In this paper, we study GF-NLFSR, a Generalized Unbalanced Feis- tel Network (GUFN) which can be considered as an extension of the outer function FO of the KASUMI block cipher. We show that the differential and linear probabilities of any n + 1 rounds of an n-cell GF-NLFSR are both bounded by p^2, where the corresponding probability of the round function is p. Besides analyzing security against differential and linear cryptanalysis, we provide a frequency distribution for upper bounds on the true differential and linear hull probabilities. From the frequency distribution, we deduce that the proportion of input-output differences/mask values with probability bounded by p^n is close to 1 whereas only a negligible proportion has probability bounded by p^2. We also recall an n^2-round integral attack distinguisher and (n^2+n-2)-round impossible impossible differential distinguisher on the n-cell GF-NLFSR by Li et al. and Wu et al. As an application, we design a new 30-round block cipher Four-Cell+ based on a 4-cell GF-NLFSR. We prove the security of Four-Cell+ against differential, linear, and boomerang attack. Four-Cell+ also resists existing key recovery attacks based on the 16-round integral attack distinguisher and 18-round impossible differential distinguisher. Furthermore, Four-Cell+ can be shown to be secure against other attacks such as higher order differential attack, cube attack, interpolation attack, XSL attack and slide attack

Parallelisable variants of Camellia and SMS4 block cipher: p-Camellia and p-SMS4

Abstract: We propose two parallelisable variants of Camellia and SMS4 block ciphers based on the n-cell GF-NLFSR. The n-cell generalised Feistel-non-linear feedback shift register (GF-NLFSR) structur

Parallelisable variants of Camellia and SMS4 block cipher : p-Camellia and p-SMS4

We propose two parallelisable variants of Camellia and SMS4 block ciphers based on the n-cell GF-NLFSR. The n-cell generalised Feistel-non-linear feedback shift register (GF-NLFSR) structure (Choy et al., 2009a) is a generalised unbalanced Feistel network that can be considered as a generalisation of the outer function FO of the KASUMI block cipher. An advantage of this cipher over other n-cell generalised Feistel networks, e.g., SMS4 (Diffe and Ledin, 2008) and Camellia (Aokiet al., 2001), is that it is parallelisable for up to n rounds. In hardware implementations, the benefits translate to speeding up encryption by up to n times while consuming similar area and significantly less power. At the same time, n-cell GF-NLFSR structures offer similar proofs of security against differential cryptanalysis as conventional n-cell Feistel structures. In this paper, we prove security against differential, linear and boomerang attacks. We also show that the selected number of rounds are conservative enough to provide high security margin against other known attacks such as integral, impossible differential, higher order differential, interpolation, slide, XSL and related-key differential attacks.NRF (Natl Research Foundation, S’pore

Identification of yeast population dynamics of spontaneous fermentation in Beijing wine region, China

The aim of this study was (i) to investigate changes occurring in the yeast population profile during spontaneous fermentation of grape juice; (ii) to assess the proliferation of commercial yeast starter culture strains in vineyards; and (iii) to identify indigenous wine strains for future development of starter strains that better reflect the yeast biodiversity of China’s grape-growing regions. To achieve this, yeasts were isolated at four different stages during fermentation of both hand-pressed and winery-sourced must samples of Vitis vinifera L. cv. Roussanne and Merlot. A total of 1600 yeast colonies were isolated and then grouped according to macroscopic and microscopic characteristics. A selection of 291 colonies from the different groups was subjected to species identification using the internal transcribed spacer regions of the 5.8S rRNA gene (ITS1-5.8S-ITS2 region) and the inter-delta () sequence of the 26S rRNA D1/D2 region. In addition, 104 Saccharomyces cerevisiae colonies were subjected to strain identification. Twelve species belonging to nine different genera were found amongst the isolates. During the early stages of fermentation, it was found that Hanseniaspora uvarum and Candida stellata numerically dominated the four to six yeast species present, including a region-specific yeast, Sporobolomyces beijingensis. Two S. cerevisiae strains were isolated from the final stage of fermentation. These two indigenous strains, which were found to be different from the nine commercial yeast strains previously used as starter cultures in this particular Beijing-based winery, might possess potentially important region-specific oenological characteristics. This study provides the first essential step towards the preservation and exploitation of the hidden oenological potential of the untapped wealth of yeast biodiversity in China’s wine-producing regions.Huihui Sun, Huiqin Ma, Meiling Hao, Isak S. Pretorius and Shangwu Chenhttp://www.annmicro.unimi.it/contents/contents59-1.ht