分组密码AES的优化与设计

AES是现有的一种抗攻击能力强、加密速度快以及可移植性好的加密算法。在FPGA上实现AES算法可以更快地处理数据。为了提高整体系统的运行速度,在优化设计中采用全流水的技术来实现算法,并对S-box进行优化。S-box是AES算法中唯一的非线性单元,在进行加密、解密尤其是在字节替换过程时,需要分别执行S-box和逆S-box,一般使用查表来进行操作,这样会占用大量的资源,所以对S-box进行优化是对整个算法优化的最重要的步骤。最终使用Modelsim对设计结果进行仿真然后使用Quartus进行总体综合。     

DES S-box generator

The Data Encryption Standard (DES) is a cryptographic algorithm, designed by IBM, that was selected to be the national standard in 1977 by the National Bureau of Standards. The algorithm itself was entirely published, but the design criteria were kept secret until 1994 when Coppersmith, one of the designers of DES, published them. He stated that the IBM team already knew about the attack called differential cryptanalysis during the design of the algorithm and that it had an effect on choosing the S-boxes. To be more specific, he mentioned eight design criteria that all the S-boxes of DES are based on. How the S-boxes were generated is a mystery, as the legend says this was outsourced to the NSA. Indeed, building a set of S-boxes respecting these criteria is not a trivial task.

In this article, the authors present an efficient S-box generator respecting all criteria and more. Coppersmith’s design criteria served as a basis, but were strengthened for better resistance to linear cryptanalysis. While other researchers have already proposed S-box generators for DES satisfying either non-linearity or good diffusion, our generator offers both. Moreover, apart from suggesting a new set of eight S-boxes, it can also very quickly produce a large pool of S-boxes to be used in further research.     

一种新的加密标准 AES

AES是一种新的加密标准，它是分组加密算法，分组长度为128位，密钥长度为128bits、192bits、256bits三种，分别称为AES－128、AES－192、AES－256。本文介绍了AES的加密算法的加密过程，函数定义，密钥扩展过程。     

一维鲁棒混沌映射及S盒的设计

本文利用Li-York混沌判别定理,构造了一类分段线性连续混沌映射.基于此类映射,建立了一个构造一类分段非线性鲁棒混沌映射的判别定理.作为应用,构造了一个由多项式函数和三角函数映射合成的分段非线性鲁棒混沌映射.通过计算该混沌映射的分岔图,验证了映射在参数范围内的混沌性.作为鲁棒混沌的应用,设计了三个基于分段非线性鲁棒混沌映射的伪随机数发生器.在此基础上,利用混沌映射对初始参数的敏感性,提出了批量生成S盒的算法.S盒密码性能的分析结果表明,生成的S盒具有良好的密码学性能,可以较好的抵抗线性与差分攻击,为密码算法的研究发展提供基础与条件.     

LITTLEWOOD'S CIPHER PART I: A CHALLENGE.

The eminent British mathematician J. E. Littlewood once invented a cipher that he claimed was unbreakable. Here I dispute this claim.     

AES S盒的马尔可夫性质研究

对AESS盒的阶次运算进行了研究,发现AESS盒的连续状态转移是一个马尔可夫链,其256个状态可以划分为5个常返态闭集,状态周期分别为59,87,81,27,2。     

A Novel Approach for Security Enhancement of Data Encryption Standard

Data Encryption Standard (DES) is a symmetric key cryptosystem that is applied in different cryptosystems of recent times. However, researchers found defects in the main assembling of the DES and declared it insecure against linear and differential cryptanalysis. In this paper, we have studied the faults and made improvements in their internal structure and get the new algorithm for Improved DES. The improvement is being made in the substitution step, which is the only nonlinear component of the algorithm. This alteration provided us with great outcomes and increase the strength of DES. Accordingly, a novel good quality S-box construction scheme has been hired in the substitution phase of the DES. The construction involves the Galois field method and generates robust S-boxes that are used to secure the scheme against linear and differential attacks. Then again, the key space of the improved DES has been enhanced against the brute force attack. The outcomes of different performance analyses depict the strength of our proposed substitution boxes which also guarantees the strength of the overall DES.     

CLEFIA-128算法的不可能差分密码分析

为研究分组密码CLEFIA-128抵抗不可能差分攻击的能力,基于一条9轮不可能差分路径,分析了13轮不带白化密钥的CLEFIA-128算法。利用轮函数中S盒差分分布表恢复部分密钥,利用轮密钥之间的关系减少密钥猜测量,并使用部分密钥分别猜测(Early Abort)技术有效地降低了复杂度。计算结果表明,该方法的数据复杂度和时间复杂度分别为O(2103.2)和O(2124.1)。     

AES的S盒和逆S盒的代数表达式

利用 域中元素自身为变量表示元素分量的代数方法求解S盒和逆S盒的代数表达式，同时解释了S盒代数表达式只有9项而逆S盒代数表达式有255项的原因，此外提出了有限域下多项式幂次运算的一种快速乘方算法，实验结果表明该算法比直接乘法运算效果好。