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assignmentutor-lab™ 为您的留学生涯保驾护航 在代写密码学cryptography theory方面已经树立了自己的口碑, 保证靠谱, 高质且原创的统计Statistics代写服务。我们的专家在代写密码学cryptography theory代写方面经验极为丰富，各种代写密码学cryptography theory相关的作业也就用不着说。

• Statistical Inference 统计推断
• Statistical Computing 统计计算
• Advanced Probability Theory 高等概率论
• Advanced Mathematical Statistics 高等数理统计学
• (Generalized) Linear Models 广义线性模型
• Statistical Machine Learning 统计机器学习
• Longitudinal Data Analysis 纵向数据分析
• Foundations of Data Science 数据科学基础

## 数学代写|密码学代写cryptography theory代考|Approaches to S-Box Design

There are currently a number of approaches to s-box design. The first method simply uses a pseudo-random number generator for each entry in the s-box (Easttom 2018a). The problem with this approach is that you will not be able to predict whether or not your s-box actually fulfills the three criteria we have outlined for an effective s-box. Instead, you will have to test extensively. A second approach is the human made. This was the method used in DES. In fact, the details of how the s-box for DES was designed are not public information. The actual s-boxes for DES are public; however, the methodology in designing them is not. These s-boxes were designed in cooperation with the National Security Agency. The final method uses some mathematical-based method to generate the values for the s-box. This is the method used in AES.

As we discussed in Chap. 6, the National Security Agency (NSA) was involved in the creation of DES. Specifically, they were deeply involved in the s-box design. In fact, one of the IBM employees who worked on DES is quoted as saying “We sent the s-boxes off to Washington. They came back and were all different.” This led many people to believe that there might be a cryptographic backdoor embedded in the DES s-boxes, which would allow the NSA to more easily break DES-encrypted communications. However, many years of study and analysis have not revealed any such backdoor.

The DES s-boxes convey a resistance to differential cryptanalysis, which we will study in Chap. 17. In fact, it has been discovered that even a small change to the DES s-box can significantly weaken its resistance to differential cryptanalysis. Differential cryptanalysis was unknown to the public at the time DES was invented. In fact, differential cryptanalysis was invented (at least publicly) by Eli Biham and Adi Shamir in the late 1980s. It is interesting to note that both Biham and Shamir noticed that DES is very resistant to differential cryptanalysis. It therefore seems most likely that the NSA was aware of differential cryptanalysis long before it was publicly known and created DES to be resistant to that attack.

## 数学代写|密码学代写cryptography theory代考|The Actual S-Boxes for DES

While the design choices themselves have not been made public, we can derive some knowledge from studying the s-boxes. As far as is publicly known, the s-boxes are not derived from a mathematical formula, as the s-boxes in AES are. It seems that each substitution was specifically and manually chosen (De Meyer and Vaudenay 2017). Figures $8.5,8.6,8.7,8.8,8.9,8.10,8.11$, and $8.12$ show DES s-boxes 1 through 8.

As you should already know, the DES s-boxes are compression s-boxes. They take in 6 input bits and produce 4 output bits. If we begin by examining the first s-box, you can see how this is done. All possible combinations of the four middle bits of the input are listed on the top row of the s-box. All possible combinations of the outer two bits are listed on the far-left column. By matching the out bits on the left with the inner bits on the top, the output bits are found. Some substitutions change several bits. For example, in s-box 1, an input of all 0 ‘s ” 000000 ” produces ” 1110 “. However, others produce far less change, for example, again focusing on s-box 1 we see that an input of 001000 produces 0010 . A simple shift of the 1 to the right.

Although most of the s-boxes provide a different substitution for any input, there is some overlap. For example, inputting 000110 in either s-box 2 or s-box 3 will produce 1110 . It is also noteworthy that there are several cases wherein different inputs to an s-box produce the same output. For example, if you consider s-box 5 notice that an input of 000001 produces 1110 . However, an input of 111110 also produces 1110 .
There has been no public disclosure of why the specific design choices for DES s-boxes were made. As we have already mentioned, resistance to differential cryptanalysis appears to have played a significant role. However, another factor is the nature of these s-boxes as compression boxes. As mentioned earlier in this chapter, it is difficult to design an s-box that uses compression without losing data. In the case of DES, it is only possible because an earlier step in the algorithm expanded bits. At least some of the design choices in DES are related to providing the compression without losing data.

# 密码学代写

## 数学代写|密码学代写cryptography theory代考| methods to S-Box Design

DES s-box传递了对差分密码分析的阻力，我们将在第17章中进行研究。事实上，人们已经发现，即使对DES s-box进行很小的更改，也可以显著削弱其对差分密码分析的抵抗力。在DES发明的时候，差分密码分析还不为公众所知。事实上，差分密码分析是由Eli Biham和Adi Shamir在20世纪80年代末发明的(至少公开)。有趣的是，Biham和Shamir都注意到DES对差分密码分析非常抵触。因此，美国国家安全局很可能早在差分密码分析被公开之前就意识到了它，并创建了DES来抵抗这种攻击

## 有限元方法代写

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## MATLAB代写

MATLAB 是一种用于技术计算的高性能语言。它将计算、可视化和编程集成在一个易于使用的环境中，其中问题和解决方案以熟悉的数学符号表示。典型用途包括：数学和计算算法开发建模、仿真和原型制作数据分析、探索和可视化科学和工程图形应用程序开发，包括图形用户界面构建MATLAB 是一个交互式系统，其基本数据元素是一个不需要维度的数组。这使您可以解决许多技术计算问题，尤其是那些具有矩阵和向量公式的问题，而只需用 C 或 Fortran 等标量非交互式语言编写程序所需的时间的一小部分。MATLAB 名称代表矩阵实验室。MATLAB 最初的编写目的是提供对由 LINPACK 和 EISPACK 项目开发的矩阵软件的轻松访问，这两个项目共同代表了矩阵计算软件的最新技术。MATLAB 经过多年的发展，得到了许多用户的投入。在大学环境中，它是数学、工程和科学入门和高级课程的标准教学工具。在工业领域，MATLAB 是高效研究、开发和分析的首选工具。MATLAB 具有一系列称为工具箱的特定于应用程序的解决方案。对于大多数 MATLAB 用户来说非常重要，工具箱允许您学习应用专业技术。工具箱是 MATLAB 函数（M 文件）的综合集合，可扩展 MATLAB 环境以解决特定类别的问题。可用工具箱的领域包括信号处理、控制系统、神经网络、模糊逻辑、小波、仿真等。

assignmentutor™您的专属作业导师
assignmentutor™您的专属作业导师