基于移位矩阵优化的LDPC码构造

环的存在对准循环LDPC（Low Density Parity Code）码的译码效率造成很大影响,拥有尽可能好的girth分布的校验矩阵对于码的性能改善有着重要的意义。首先对准循环LDPC码校验矩阵的girth分布进行分析,然后在母矩阵和移位矩阵之间设定一个合理的约束关系,使得构造后的校验矩阵最小环长及平均最小环长追求最大化,最后提出了一种易于实现的具有高girth的QC-LDPC（Quasi cyclic-Low Density Parity Code）码构造方法。仿真结果表明,该方法尽量减少码中的短循环,能构造实用化的好码。     

具有几乎完美代数免疫的偶数元弹性函数构造

完美代数免疫(PAI)的布尔函数能够抵御代数攻击和快速代数攻击。PAI函数的构造是目前布尔函数研究最具挑战性的问题之一。利用布尔函数的双变元表达式和有限域理论,基于Carlet-Feng函数提出一种新的偶数元布尔函数的一般性构造。证明由该构造得到的函数具有一阶弹性和至少次优代数免疫度等密码学性质,给出其代数免疫度达到最优时的充分条件,并比较该类函数、Carlet-Feng函数和由一阶级联方式构造的函数在6~16之间的所有偶数变元下抵抗快速代数攻击能力。实验结果表明,该类函数能更好地抵抗快速代数攻击,且具有几乎完美的代数免疫性能。     

具有不可链接性的无线通信匿名认证

客户端-服务器认证协议的匿名性指服务器能够认证客户端的真实性,但无法获知客户端的身份。针对认证协议提出了新的安全性需求—不可链接性,该性质是对匿名性的有益补充。对已有文献中的认证协议进行修正,使其在不降低认证效率的前提下满足不可链接性。修正后的方案同时提供身份保护性、不可链接性、双向认证、密钥协商、密钥更新、会话密钥的后向保密性以及客户端的口令修改功能。     

机密过程模型：一种量化机密泄漏的方法

In this paper, we propose a theoretical-in-formation Confidential Procedure Model (CPM) to quantify confidentiality ( or information leakage ). The advantages of the CPM model include the fol-lowing: 1) confidentiality loss is formalized as a dy-namic procedure, instead of a static function, and described via the “waterfall” diagram; 2) confiden-tiality loss is quantified in a relative manner, i. e., taken as a quantitative metric, the ratio of the condi-tional entropy being reserved after observing the entropy of the original full confidential information; 3) the optimal attacks including exhaustive attacks as well as all possible attacks that have (or have not even) been discovered, are taken into account when defining the novel concept of the confidential de-gree. To elucidate the proposed model, we analyze the information leakage in side-channel attacks and the anonymity of DC-net in a quantitative manner.     

内置确定性子密钥相关系数功耗分析

针对Komano等(KOMANO Y, SHIMIZU H, KAWAMURA S. BS-CPA: built-in determined sub-key correlation power analysis. IEICE Transactions on Fundamentals of Electronics, Communications and Computer Sciences, 2010,E93-A(9):1632-1638.)对dpacontest.org平台提供的数据进行研究后提出的内置确定性子密钥相关系数功耗分析（BS-CPA）方法进行分析,并从破解所需功耗数据和成功率方面将BS-CPA与差分功耗分析（DPA）、相关系数功耗分析（CPA）进行比较分析,发现BS-CPA虽然理论上方法可行,但远未达到其声称的效果,进而从密码设备加密过程中寄存器状态的变化与功耗值的关系来选取中间变量,通过去除噪声和错误峰值,找到与密钥最相关数据点来缩小攻击范围。对于相同数量功耗数据,部分点攻击与全部点攻击相比,完全破解64位密钥的成功率最大可以提高60%。实验结果表明改进后的模型攻击效率得到提升,达到同样成功率需要功耗数据少,攻击结果稳定。     

改进同态图像秘密共享ElGamal ECC加密体制

针对Li等人提出的ElGamal椭圆加密体制进行改进,该方案不需要增加计算开销就能提高接收者验证图像正确性的能力.一旦接收者发现加密图像的某些块被污染或者窜改,可立即丢掉这个图像,不需要等到整个图像完全解密出来后才判断出此图像已损坏.结果表明本方案能够对图像快速处理,提高验证速度,减少计算开销.     

基于初等数论的圈长8规则准循环LDPC码

This paper is concerned with (3, n ) and (4, n ) regular quasi-cyclic Low Density Parity Check (LDPC) code constructions from elementary number theory. Given the column weight, we determine the shift values of the circulant permutation matrices via arithmetic analysis. The proposed constructions of quasi-cyclic LDPC codes achieve the following main advantages simultaneously: 1) our methods are constructive in the sense that we avoid any searching process; 2) our methods ensure no four or six cycles in the bipartite graphs corresponding to the LDPC codes; 3) our methods are direct constructions of quasi-cyclic LDPC codes which do not use any other quasi-cyclic LDPC codes of small length like component codes or any other algorithms/cyclic codes like building block; 4)the computations of the parameters involved are based on elementary number theory, thus very simple and fast. Simulation results show that the constructed regular codes of high rates perform almost 1.25 dB above Shannon limit and have no error floor down to the bit-error rate of 10-6 .     

基于广义切比雪夫多项式的身份基加密体制安全性分析

Chebyshev polynomials are used as a reservoir for generating intricate classes of symmetrical and chaotic patterns, and have been used in a vast amount of applications. Using extended Chebyshev polynomial over finite field Zp , Algehawi and Samsudin presented recently an Identity Based Encryption (IBE) scheme. In this paper, we showed their proposal is not as secure as they claimed. More specifically, we presented a concrete attack on the scheme of Algehawi and Samsudin, which indicated the scheme cannot be consolidated as a real alternative of IBE schemes since one can exploit the semi group property (bilinearity) of extended Chebyshev polynomials over Zp to implement the attack without any difficulty.     

基于圆锥曲线的数字签名与多签名体制

数字签名和多签名体制是密码学中的重要方向,目前有许多方案被设计出来。然而,从查阅文献来看,很少有基于圆锥曲线的数字签名或多签名体制。利用圆锥曲线构造了一个数字签名体制,该体制能够提供阈下信道特性,然后基于这个数字签名体制设计了一个多签名方案。两个方案的安全性依赖于圆锥曲线上的离散对数问题。