Security Analysis of A Stream Cipher with Proven Properties

Si and Ding proposed a stream cipher with two keys (the first and the second key) and an expected security strength. To further measure the security, we analyze the stream cipher by considering the selective discrete Fourier spectra attack and the fast selective discrete Fourier spectra attack. The two attacks reveal a fact that the second key is more important than the first key, that is, if the second key is leaked out, the first key can be obtained with a lower time complexity than that of the expected security. In addition, we analyze the ability of the stream cipher to resist the guess-and-determine attack. The results show an attacker is able to gain the two keys with an exponentially improved time complexity and a polynomial data complexity. It implies that we need a securer permutation over finite fields to design a new binary additive stream cipher to achieve the expected security level.     

Collision analysis of the GMR-2 cipher used in the satellite phone

A collision property analysis of the GMR-2 cipher used in the satellite phone was presented.By using the F-component as a bridge,the link between the difference of the key byte and the collision of the output ofFas well as the link between the collision of the output of F and the collision of keystream byte were analyzed,which finally revealed the relationship between the difference of the original key byte and the keystream collision.The theoretical analysis showed that for a random frame number,a special chosen key pair could lead to a keystream collision with a high probability,when the key pair has only one byte difference in which the most significant 4 bit of the difference was equal to the last significant 4 bit.The experimental result shows that the keystream collision probability is 2^?8.248,which is far higher than the ideal collision probability 2^?120.This proves once again,that there exists serious potential security hazards in the GMR-2 cipher.     

k-error linear complexity of q-ary sequence of period p2

Based on element statistics in a matrix,a new efficient computing method for computing the k-error linear complexity of q-ary sequence of period p²was proposed,where p,q were odd primes and q modulo p²was primitive.A general result and a concrete proof were showed.To verify the correctness of the result,two kinds of q-ary sequence of period p²were illustrated.Because the new method does not need iterative calculation and when it is implemented by program and compared with existing algorithms,the results show that the proposed new algorithm is significantly more efficient in calculating k-error linear complexity of q-ary sequence of period p².     

融合人脸特征与密码算法的身份认证系统

利用人脸识别技术、活体检测技术,结合国密算法,设计了一个基于模糊承诺算法的身份认证系统。提出一种多值量化方法来提高数据相似性,并采用多样本组的特征数据清洗方式提高数据稳定性,以解决常见的生物特征认证中误识率和拒识率较高且难以平衡的问题。在注册阶段,采集多组128维人脸特征数据,清洗后获得平均值,基于一个阈值区间将每个维度的数据量化为4 b二进制数。将量化完成后的数据作为加密密钥,以BCH编码为纠错码,使用模糊承诺算法将认证服务器产生的秘密密钥加密存储在客户端。在认证阶段,实时采集的人脸特征数据经过量化后,利用BCH纠错提取出秘密密钥,将秘密密钥作为协商密钥,基于传统身份认证协议实现客户端与认证服务器之间的认证过程。通过实验证实,采用上述方法实现的身份认证系统可将误识率降低至0%,拒识率降低到1%以内。     

基于DSP的DVB流发射/接收系统

研究了数字视频广播流的发射／接收系统,基于DSP技术实现了0～8Mbps的DVB流的发射和接收系统,误码率低于10^-7,详细介绍了发射／接收系统数据处理原理,探讨了相关系统硬件设计和软件实现问题。     

分组密码算法及一种分类法

介绍了20余种分组密码算法,这些算法反应了近年来分组密码算法的发展,其中有些已经或将可能用于现代通信网,特别是用在Internet中。另外还介绍了分组密码的一种新的分类方法,它可能为分组密码的分析和设计提供一点新的思路。     

CS-CIPHER两个变体的线性密码分析

CS-CIPHER是NESSIE公布的17个候选算法之一,它的分组长度为64-比特.本文对CS-CIPHER的两个变体进行了线性密码分析.对第一个变体的攻击成功率约为78.5%,数据复杂度为2⁵²,处理复杂度为2³².对第二个变体的攻击成功率约为78.5%,数据复杂度为2⁵²,处理复杂度为2¹¹².     

一种基于“编织法”的de Bruijn序列构造算法

文章首先给出n级de Bruijn序列通过"编织法"所产生序列的周期,并证明其中所有2n长状态两两不同.之后,论证出平移等价意义下一条n级de Bruijn序列仅能编织出两条序列.最后针对每一条序列,补全其缺失的四个2n长状态即可构造出2n级de Bruijn序列.由于增添比特的方式有两种,因此由一条n级de Bruijn序列可构造出四条2n级de Bruijn序列.     

Diffusion and Security Evaluation of Feistel-PG

Feistel-PG structure is a new specific Gen-eralized Feistel structure (GFS) adopted in DBlock and LHash. Its main feature is adding a sbox-size permutation before the round function. Different choices of the per-mutation may aff ect the security property of ciphers with Feistel-PG structure but how it eff ects is not clear. We evaluate the values of diffusion round for all possible pa-rameters and summarize the characteristics of optimum shuffles. The results show that one special kind of Feistel-PG achieves full diffusion in less cost than the improved GFS. This advantage may attract the designers' interests and this kind of Feistel-PG ciphers are suggested to de-signers. We also evaluate the security of suggested ciphers against various byte-oriented attacks, including differential cryptanalysis, linear cryptanalysis, impossible differential attack and integral attack. Some permutations with opti-mum diffusion but relatively weaker security are filtered out and these permutations should be avoided by design-ers.     

基于先验结果对涂-邓猜想一些情形下的递推证明

对于涂（自然）-邓（映蒲）提出的一个二元组合猜想,已验证了k≤39时的情形,本文在此基础上利用递推归纳的方法,给出了对任意的k,t≤219情形下涂-邓猜想的正确性证明.