复合加密系统中DES算法的实现

电子通信论文编号:TX041       论文字数:25448,页数:78

目    录
引言   1
1. 密码学的概述   3
1.1 加密的概念   3
1.2 加密的理由   3
1.3 加密的基本原理   4
1.4 密码分析学   5
2  数学基础   7
2.1 数论基础   7
2.1.1整除   7
2.1.2素数   8
2.1.3欧拉函数(n)   8
2.1.4最大公约数与最小公倍数   9
2.1.5欧几里德(Euclid)算法   10
2.2 计算复杂性理论基础   11
2.2.1算法与问题   12
2.2.2算法的复杂性   12
2.2.3问题的复杂性   13
3.  DES算法  14
3.2.2子密钥的生成   18
3.2.3 解密   20
3.3 DES的安全性分析   21
4.  系统需求分析   22
4.1 系统设计的目标   22
4.2 系统要实现的主要功能   22
5.  系统设计实现  23
5.1 概要设计   23
5.2  详细设计   24
5.2.1打开文件模块设计   24
5.2.2密钥管理模块设计   25
5.2.3加密、解密模块设计   27
5.2.4 简单的帮助模块  32
6.  系统测试   32
6.1 系统测试的目的   33
6.2 测试的原则   33
6.3  测试步骤  33
6.3.1单元测试  33
6.3.2集成测试   37
6.3.3确认测试  37
7. 结论  37
谢  词  38
参考文献  39
附录：主要源程序   40

摘  要：

随着信息化和数字化社会的发展，人们对信息安全和保密的重要性认识不断提高，加密在当今社会生活的各个方面起着极其重要作用，与之对应的密码学是一门交叉学科，它在很大程度上是一门应用数学学科，密码学中涉及到数论、代数、计算复杂性理论、组合数学等多种数学知识。
数据加密标准(DES)是美国国家标准局公开征集的一种用于政府部门以及民间进行计算机数据加密的密码算法，其目的是为了满足计算机通信网络的发展对安全保密的需求，实现系统同一水平的安全性和兼容性，同时降低数据加密产品的生产成本，DES的出现是密码学历史上的一个重要事件，它是密码学历史上第一个广泛应用于商用数据保密、公开的密码算法，它开创了公开密码算法的先例。
本文简单介绍了密码学及其相关理论知识，叙述了DES加密算法的的历史、现状和原理。介绍了加密的数学基础；详细阐述了DES加密算法的原理；详细的讲解了DES加密的系统的设计目的、所实现的功能和每一步的详细设计，以及对系统测试的结果。附录部分有DES加密系统的主要源代码。

关键字：数据加密标准；加密；密钥

Abstract

With the development of information and digitized society, people’s cognition about safety to information and importance of secrecy improve constantly, today, encryption plays an extremely important role on all respects of social life, it is a cross discipline with its corresponding cryptography , it is a applied mathematics discipline to a great extent, Cryptography include many kinds of mathematics knowledge, such as number theory, algebra, the complexity of calculation theory and combinatorial mathematics.

Data encryption standard (DES) is a algorithm that NBS collected publicly used for government department and folk to encrypt computer datum, its purpose is suffice to the demand of the development of the communication network of the computer to the safety and secrecy, security and compatibility of the same level of the implementation system, and reduce the cost of  the data encrypted productions at the same time , appearance of DES cryptography is a important incident of history, it cryptography first apply commercial datum keep secret, open password algorithm extensively in history, it starts the precedent of the open password algorithm.

This study has introduced cryptography and relevant theory knowledge, history, current situation and principle of the ones that have narrated DES and encrypt the algorithm briefly. Have introduced the mathematics foundation encrypted; Have explained in detail that DES encrypts the principle of the algorithm; Purpose of design, function realized and every steps of detailed designs of system that detailed explanation DES encrypts, and the result to system testing. The part of the appendix has main source code that DES encrypted the system.

Key word: Data Encryption Standard (DES); Encrypt; Key.