排序方式: 共有84条查询结果,搜索用时 15 毫秒
1.
We present a practical polynomial-time algorithm for computing the
zeta function of a Kummer curve over a finite field of small
characteristic. Such algorithms have recently been obtained using a
method of Kedlaya based upon Monsky–Washnitzer cohomology, and are of
interest in cryptography. We take a different approach.
The problem is reduced to that of computing the L-function
of a multiplicative character sum. This latter task is achieved via a
cohomological formula based upon the work of Dwork and Reich. We show,
however, that our method and that of Kedlaya are very closely related.Dedicated to the memory of Gian-Carlo Rota 相似文献
2.
3.
We provide conditions for which the round functions of an ?-bit Rijndael-like block cipher generate the alternating group on the set {0,1}?. These conditions show that the class of Rijndael-like ciphers whose round functions generate the alternating group on their message space is large, and includes both the actual Rijndael and the block cipher used by the compression function of the Whirlpool hash function. The result indicates that there is no trapdoor design for a Rijndael-like cipher based on the imprimitivity of the group action of its proper round functions which is difficult to detect. 相似文献
4.
Nicholas Kolokotronis 《Designs, Codes and Cryptography》2008,46(3):353-363
The cryptographic properties of keystreams generated by stream ciphers based on t-functions are studied. These constructions
are of great interest as they allow building highly efficient and secure cryptographic primitives. The randomness of the coordinate
sequences generated by such mappings is analyzed in terms of the autocorrelation function. The results derived are valid for
all t-functions regardless the type of construction and indicate the existence of nonrandomness. As the problem of the efficient
implementation of secure s-boxes is open, the nonlinearity of t-functions is also analyzed. It is shown how some cryptographically
undesirable properties, can be solved by application of similarity transformations.
相似文献
5.
We present a novel multi-image encryption and decryption algorithm based on Fourier transform and fractional Fourier transforms. Lower frequency parts of the original images are selected, frequency shifted and encrypted by using double phase encoding in fractional Fourier domains. Multiple images are encrypted together into a single one. A simple optical setup is given to implement the proposed algorithm. This scheme has features of enhancement in decryption accuracy and high optical efficiency. Numerical results have been given to verify the validity and efficiency of the proposed scheme. 相似文献
6.
In this paper via a novel method of discretized continuous-time Kalman filter, the problem of synchronization and cryptography in fractional-order systems has been investigated in presence of noisy environment for process and output signals. The fractional-order Kalman filter equation, applicable for linear systems, and its extension called the extended Kalman filter, which can be used for nonlinear systems, are derived. The result is utilized for chaos synchronization with the aim of cryptography while the transmitter system is fractional-order, and both the transmitter and transmission channel are noisy. The fractional-order stochastic chaotic Chen system is then presented to apply the proposed method for chaotic signal cryptography. The results show the effectiveness of the proposed method. 相似文献
7.
Jaume Martí-Farré 《Discrete Applied Mathematics》2006,154(3):552-563
The characterization of ideal access structures and the search for bounds on the optimal information rate are two important problems in secret sharing. These problems are studied in this paper for access structures with intersection number equal to one, that is, structures such that there is at most one participant in the intersection of any two different minimal qualified subsets. The main result in this work is the complete characterization of the ideal access structures with intersection number equal to one. In addition, bounds on the optimal information rate are provided for the non-ideal case. 相似文献
8.
正形置换在密码学中有着广泛的应用,利用m-序列的"三项式特性",给出了一个构造n元正形置换的新方法,该方法既不同于已有的由n-2元构造n元正形置换,也不同于基于正交拉丁方的由n元构造n+1元正形置换的方法. 相似文献
9.
A.M. Youssef 《Discrete Mathematics》2006,306(16):2016-2020
Several recently proposed block ciphers such as AES, Camellia, Shark, Square and Hierocrypt use s-boxes that are based on the inversion mapping over GF(2n). In order to hide the simple algebraic structure in this mapping, an affine transformation over F2 is usually used after the output of the s-box. In some ciphers, an additional affine transformation is used before the input of the s-box as well. In this paper, we study the algebraic properties of a simple approximation in the form s(x)=ax-1+b, a,b∈GF(2n) for such s-boxes. The implication of this result on the cryptanalysis of these ciphers remains an open problem. 相似文献
10.
Maura Paterson 《Designs, Codes and Cryptography》2007,42(2):195-212
A sliding-window dynamic frameproof code is a scheme for discouraging the piracy of digital broadcasts through the use of
digital fingerprinting. In this paper, we formally define sliding-window dynamic frameproof codes and provide optimal constructions
for a certain class of these schemes. We also discuss bounds on the number of users such schemes can support.
相似文献