Analysis of Minimum Numbers of Linearly Active S-Boxes of a Class of Generalized Feistel Block Ciphers

For a class of generalized Feistel block ciphers, an explicit recurrent formula for the minimum numbers of linearly active $S$-boxes of any round $r$ is presented

Loiss: A Byte-Oriented Stream Cipher

This paper presents a byte-oriented stream cipher -- Loiss, which takes a 128-bit initial key and a 128-bit initial vector as inputs, and outputs a key stream of bytes. The algorithm is based on a linear feedback shift register, and uses a structure called BOMM in the filter generator, which has good property on resisting against algebraic attacks, linear distinguishing attacks and fast correlation attacks. In order for BOMM to be balanced, the S-boxes in BOMM must be orthomorphic permutations. To further improve the capability in resisting against those attacks, the S-boxes in BOMM must also possess some good cryptographic properties, for example, high algebraic immunity, high nonlinearity, and so on. However current researches on orthomorphic permutations pay little attention on their cryptographic properties, and we believe that Loiss not only enriches applications of orthomorphic permutations in cryptography, but also motivates the research on a variety of cryptographic properties of orthomorphic permutations

Assessment of Runoff and Sediment Yields Using the AnnAGNPS Model in a Three-Gorge Watershed of China

Soil erosion has been recognized as one of the major threats to our environment and water quality worldwide, especially in China. To mitigate nonpoint source water quality problems caused by soil erosion, best management practices (BMPs) and/or conservation programs have been adopted. Watershed models, such as the Annualized Agricultural Non-Point Source Pollutant Loading model (AnnAGNPS), have been developed to aid in the evaluation of watershed response to watershed management practices. The model has been applied worldwide and proven to be a very effective tool in identifying the critical areas which had serious erosion, and in aiding in decision-making processes for adopting BMPs and/or conservation programs so that cost/benefit can be maximized and non-point source pollution control can be achieved in the most efficient way. The main goal of this study was to assess the characteristics of soil erosion, sediment and sediment delivery of a watershed so that effective conservation measures can be implemented. To achieve the overall objective of this study, all necessary data for the 4,184 km2 Daning River watershed in the Three-Gorge region of the Yangtze River of China were assembled. The model was calibrated using observed monthly runoff from 1998 to 1999 (Nash-Sutcliffe coefficient of efficiency of 0.94 and R2 of 0.94) and validated using the observed monthly runoff from 2003 to 2005 (Nash-Sutcliffe coefficient of efficiency of 0.93 and R2 of 0.93). Additionally, the model was validated using annual average sediment of 2000–2002 (relative error of −0.34) and 2003–2004 (relative error of 0.18) at Wuxi station. Post validation simulation showed that approximately 48% of the watershed was under the soil loss tolerance released by the Ministry of Water Resources of China (500 t·km−2·y−1). However, 8% of the watershed had soil erosion of exceeding 5,000 t·km−2·y−1. Sloping areas and low coverage areas are the main source of soil loss in the watershed

Drivers of cropland abandonment in mountainous areas: A household decision model on farming scale and a case study of Southwest China

Cropland abandonment has emerged as a prevalent phenomenon in the mountainous areas of China.While there is a general understanding that this new trend is driven by the rising opportunity cost of rural labor, rigorous theoretical and empirical analyses are largely absent. This paper first develops a theoretical model to investigate household decisions on farming scale when off-farm labor market is accessible and there is heterogeneity of farmland productivity and distribution. The model is capable of explaining the hidden reasons of cropland abandonment in sloping and agriculturally less-favored locations. The model also unveils the impacts of heterogeneity of household labor on fallow decisions and the efficiency loss due to an imperfect labor market. The model is empirically tested by applying the Probit and Logit estimators to a unique household and land-plot survey dataset which contains 5258 plots of599 rural households in Chongqing, a provincial level municipality, in Southwest China. The survey shows that more than 30% of the sample plots have been abandoned, mainly since 1992. The econometric results are consistent with our theoretical expectations. This work would help policy-makers and stakeholders to identify areas with a high probability of land abandonment and farming practice which is less sustainable in the mountainous areas

asymptotic granularity reduction and its application

It is well known that the inverse function of y=x with the derivative y′=1 is x=y, the inverse function of y=c with the derivative y′=0 is nonexistent, and so on. Hence, on the assumption that the noninvertibility of the univariate increasing function y=f(x) with x>0 is in direct proportion to the growth rate reflected by its derivative, the authors put forward a method of comparing difficulties in inverting two functions on a continuous or discrete interval called asymptotic granularity reduction (AGR) which integrates asymptotic analysis with logarithmic granularities, and is an extension and a complement to polynomial time (Turing) reduction (PTR). Prove by AGR that inverting y≡xx(modp) is computationally harder than inverting y≡gx(modp), and inverting y≡gxn(modp) is computationally equivalent to inverting y≡gx(modp), which are compatible with the results from PTR. Besides, apply AGR to the comparison of inverting y≡xn(modp) with y≡gx(modp), y≡gg1x(modp) with y≡gx(modp), and y≡xn+x+1(modp) with y≡xn(modp) in difficulty, and observe that the results are consistent with existing facts, which further illustrates that AGR is suitable for comparison of inversion problems in difficulty. Last, prove by AGR that inverting y≡xngx(modp) is computationally equivalent to inverting y≡gx(modp) when PTR cannot be utilized expediently. AGR with the assumption partitions the complexities of problems more detailedly, and finds out some new evidence for the security of cryptosystems. © 2011 Elsevier B.V. All rights reserved

analysis of minimum numbers of linearly active s-boxes of a class of generalized feistel block ciphers

For a class of generalized Feistel block ciphers, an explicit formula for the minimum numbers of linearly active S-boxes of any round r is presented. © 2012 Institute of Systems Science, Academy of Mathematics and Systems Science, CAS and Springer-Verlag Berlin Heidelberg.For a class of generalized Feistel block ciphers, an explicit formula for the minimum numbers of linearly active S-boxes of any round r is presented. © 2012 Institute of Systems Science, Academy of Mathematics and Systems Science, CAS and Springer-Verlag Berlin Heidelberg

national security vulnerability database classification based on an lda topic model

采用隐含Dirichlet分布主题模型(latent Dirichletallocation,LDA)和支持向量机(support vector machine,SVM)相结合的方法,在主题向量空间构建一个自动漏洞分类器。以中国国家信息安全漏洞库(CNNVD)中漏洞记录为实验数据。实验表明:基于主题向量构建的分类器的分类准确度比直接使用词汇向量构建的分类器有8%的提高。国家重点科技专题“核高基”资助项目(2010ZX01036-001-002)The current vulnerabilities in China are analyzed using a dataset from the China National Vulnerability Database of Information Security (CNNVD), with a combined latent Dirichlet allocation (LDA) topic model and a support vector machine (SVM) to construct a classifier in the topic vector space. Tests show that the classifier based on topic vectors has about 8% better classification performance than that based on text vectors

on the probability distribution of the carry cells of stream ciphers f-fcsr-h v2 and f-fcsr-h v3

F-FCSR-H v2 is one of the 8 final stream ciphers in the eSTREAM portfolio. However, it was broken by M. Hell and T. Johansson at ASIACRYPT 2008 by exploiting the bias in the carry cells of a Galois FCSR. In order to resist this attack, at SAC 2009 F. Arnault proposed the new stream cipher F-FCSR-H v3 based upon a ring FCSR. M. Hell and T. Johansson only presented experimental results but no theoretical results for the success probability of their powerful attack against F-FCSR-H v2. And so far there are no analytical results of F-FCSR-H v3. This paper discusses the probability distribution of the carry cells of F-FCSR-H v2 and F-FCSR-H v3. We build the probability model for the carry cells of the two stream ciphers and prove that the consecutive output sequence of a single carry cell is a homogeneous Markov chain and the inverse chain is also a homogeneous Markov chain. We also prove that the probability of l consecutive outputs of a single carry cell to be zeros is (1/2)&middot(3/4) l∈-∈1, which is a weakness of the carry cells of F-FCSR-H v2 and F-FCSR-H v3, noticing that (1/2)&middot(3/4) l∈-∈1∈>∈2-∈l for l∈>∈1. FCSR is a finite-state automata, so its distribution is stable. Based on this fact, we construct a system of equations using the law of total probability, and present a theoretical probability of breaking F-FCSR-H v2 by solving the equations. Applying this technique to F-FCSR-H v3, we obtain that the probability of all the 82 carry cells of F-FCSR-H v3 to be zeros at the same clock is at least 2-∈64.29, which is much higher than 2-∈82. This is another weakness of the carry cells of F-FCSR-H v3. Our results provide theoretical support to M.Hell and T.Johansson's cryptanalysis of F-FCSR-H v2 and establish a theoretical foundation for further cryptanalysis of F-FCSR-H v3. © 2012 Springer-Verlag Berlin Heidelberg.F-FCSR-H v2 is one of the 8 final stream ciphers in the eSTREAM portfolio. However, it was broken by M. Hell and T. Johansson at ASIACRYPT 2008 by exploiting the bias in the carry cells of a Galois FCSR. In order to resist this attack, at SAC 2009 F. Arnault proposed the new stream cipher F-FCSR-H v3 based upon a ring FCSR. M. Hell and T. Johansson only presented experimental results but no theoretical results for the success probability of their powerful attack against F-FCSR-H v2. And so far there are no analytical results of F-FCSR-H v3. This paper discusses the probability distribution of the carry cells of F-FCSR-H v2 and F-FCSR-H v3. We build the probability model for the carry cells of the two stream ciphers and prove that the consecutive output sequence of a single carry cell is a homogeneous Markov chain and the inverse chain is also a homogeneous Markov chain. We also prove that the probability of l consecutive outputs of a single carry cell to be zeros is (1/2)&middot(3/4) l∈-∈1, which is a weakness of the carry cells of F-FCSR-H v2 and F-FCSR-H v3, noticing that (1/2)&middot(3/4) l∈-∈1∈>∈2-∈l for l∈>∈1. FCSR is a finite-state automata, so its distribution is stable. Based on this fact, we construct a system of equations using the law of total probability, and present a theoretical probability of breaking F-FCSR-H v2 by solving the equations. Applying this technique to F-FCSR-H v3, we obtain that the probability of all the 82 carry cells of F-FCSR-H v3 to be zeros at the same clock is at least 2-∈64.29, which is much higher than 2-∈82. This is another weakness of the carry cells of F-FCSR-H v3. Our results provide theoretical support to M.Hell and T.Johansson's cryptanalysis of F-FCSR-H v2 and establish a theoretical foundation for further cryptanalysis of F-FCSR-H v3. © 2012 Springer-Verlag Berlin Heidelberg

on the nonexistence of nontrivial small cycles of the μ function in 3x+1 conjecture

This paper studies the property of the recursive sequences in the 3x + 1 conjecture. The authors introduce the concept of μ function, with which the 3x + 1 conjecture can be transformed into two other conjectures: one is eventually periodic conjecture of the μ function and the other is periodic point conjecture. The authors prove that the 3x + 1 conjecture is equivalent to the two conjectures above. In 2007, J. L. Simons proved the non-existence of nontrivial 2-cycle for the T function. In this paper, the authors prove that the μ function has no l-periodic points for 2 &le l &le 12. In 2005, J. L. Simons and B. M. M de Weger proved that there is no nontrivial l-cycle for the T function for l &le 68, and in this paper, the authors prove that there is no nontrivial l-cycle for the μ function for 2 &le l &le 102. © 2012 Institute of Systems Science, Academy of Mathematics and Systems Science, CAS and Springer-Verlag Berlin Heidelberg.This paper studies the property of the recursive sequences in the 3x + 1 conjecture. The authors introduce the concept of μ function, with which the 3x + 1 conjecture can be transformed into two other conjectures: one is eventually periodic conjecture of the μ function and the other is periodic point conjecture. The authors prove that the 3x + 1 conjecture is equivalent to the two conjectures above. In 2007, J. L. Simons proved the non-existence of nontrivial 2-cycle for the T function. In this paper, the authors prove that the μ function has no l-periodic points for 2 &le l &le 12. In 2005, J. L. Simons and B. M. M de Weger proved that there is no nontrivial l-cycle for the T function for l &le 68, and in this paper, the authors prove that there is no nontrivial l-cycle for the μ function for 2 &le l &le 102. © 2012 Institute of Systems Science, Academy of Mathematics and Systems Science, CAS and Springer-Verlag Berlin Heidelberg