Stream function finite element solution of Stokes flow with penalties

A finite element method for solution of the stream function formulation of Stokes flow is developed. The method involves complete cubic non-conforming (C⁰) triangular Hermite elements. This element fails the patch test. To correct the element and produce a convergent method we employ a penalty method to weakly enforce the desired continuity constraint on the normal derivative across the inter-element boundaries. Successful use of the method is demonstrated to require reduced integration of the inter-element penalty with a 1-point Gauss rule. Error estimates relate the optimal choice of penalty parameter to mesh size and are corroborated by numerical convergence studies. The need for reduced integration is interpreted using rank relations for an associated hybrid method.     

信源平衡编码及其在流密码中的应用

本文对离散无记忆信源给出了一种编码方法，它使编码后信源输出有着最好的平衡性，即0与1的数目最大程度地接近．对等长编码，本文给出的方法是步优的；对基于Huffman码的平衡编码，在保持平均码长不变的情况下，本文给出的方法使0与1的平衡性达到最优．因为一般信源字符的频率是一个统计数字．这里的平衡性也是从统计角度来说的．最后我们还讨论了这种平衡编码对流密码中的非线性组合器在防止相关攻击方面的防护作用．     

信息反馈流密码体制

传统流密码体制的安全性已越来越严重地受到各种攻击的威胁,对此人们在尽各种努力寻找新型的安全体制。本文发展了早期人们考虑到的信息反馈流密码体制,分析了它们的安全性并指出这种新型流密码的实用价值。初步分析表明,信息反馈流密码体制具有较高的安全性。     

Bent函数在流密码中的应用

本文利用频谱方法研究了Bent函数在流密码中的应用,指出Bent函数具有最高的非线性度,用它作非线性组合器中的组合函数不但可很好地抗相关攻击,而且可最大程度地抗最佳线性逼近攻击。本文还对Bent函数进行了改造以满足平衡性等要求。     

黄石广电互动电视平台建设实践

介绍了黄石广电在数字化整转后,采用UT斯达康Rolling Stream系统,基于HFC+IPQAM方式建立互动电视平台的实践过程.     

Security analysis of mCrypton proper to low‐cost ubiquitous computing devices and applications

mCrypton, which is a mini‐version of Crypton, is a 64‐bit block cipher with three key size options (64 bits, 96 bits, 128 bits). It was designed for use in low‐cost ubiquitous wireless devices and resource‐constrained tiny devices such as low‐cost Radio‐Frequency Identification tags and sensors in Ubiquitous Sensor Network. In this paper we show that 8‐round mCrypton with 128‐bit key is vulnerable to related‐key rectangle attack. We first describe how to construct two related‐key truncated differentials on which 7‐round related‐key rectangle distinguisher is based and then we exploit it to attack 8‐round mCrypton. This attack requires 2⁴⁶ dada and 2⁴⁶ time complexities, which is faster than exhaustive search. This is the first known cryptanalytic result on mCrypton. Copyright © 2009 John Wiley & Sons, Ltd.     

Cryptanalysis of an E0-like Combiner with Memory

In this paper, we study an E0-like combiner with memory as the keystream generator. First, we formulate a systematic and simple method to compute correlations of the FSM output sequences (up to certain bits). An upper bound of the correlations is given, which is useful to the designer. Second, we show how to build either a uni-bias-based or multi-bias-based distinguisher to distinguish the keystream produced by the combiner from a truly random sequence, once correlations are found. The data complexity of both distinguishers is carefully analyzed for performance comparison. We show that the multi-bias-based distinguisher outperforms the uni-bias-based distinguisher only when the patterns of the largest biases are linearly dependent. The keystream distinguisher is then upgraded for use in the key-recovery attack. The latter actually reduces to the well-known Maximum Likelihood Decoding (MLD) problem given the keystream long enough. We devise an algorithm based on Fast Walsh Transform (FWT) to solve the MLD problem for any linear code with dimension L and length n within time O(n+L⋅2 ^L ). Meanwhile, we summarize a design criterion for our E0-like combiner with memory to resist the proposed attacks.     

物联网发展中的安全风险及对策研究

分析了国内外物联网安全政策、技术、标准、产业等形势,重点强调了当前我国物联网发展中存在的安全风险,包括大连接环境下的设备风险、物联网网络本身安全风险以及物联网上承载的各类应用安全风险,提出了打造以密码为核心的物联网安全体系,加速新技术在物联网安全的应用,以新基建为契机建立物联网领域安全设备泛在化部署新体系,以多层次立体式理念确保物联网安全,呼吁供给侧需求侧建立安全协同新机制,共同促进物联网产业安全可持续发展。     

Improved impossible differential and biclique cryptanalysis of HIGHT

HIGHT is a lightweight block cipher introduced in CHES 2006 by Hong et al as a block cipher suitable for low‐resource applications. In this paper, we propose improved impossible differential and biclique attacks on HIGHT block cipher both exploiting the permutation‐based property of the cipher's key schedule algorithm as well as its low diffusion. For impossible differential attack, we found a new 17‐round impossible differential characteristic that enables us to propose a new 27‐round impossible differential attack. The total time complexity of the attack is 2^120.4 where an amount of 2^59.3 chosen plaintext‐ciphertext pairs and 2^107.4 memory are required. We also instantiate a new biclique cryptanalysis of HIGHT, which is based on the new idea of splitting each of the forward and backward keys into 2 parts where the computations associated to each one are performed independently. The time complexity and data complexity of this attack are 2^125.7 and 2⁴², respectively. To the best of our knowledge, this is the fastest biclique attack on full‐round HIGHT.