【作者】 王娟；

【导师】 胡汉平；

【作者基本信息】 华中科技大学 ， 信息安全， 2007， 硕士

【摘要】 密码是信息安全技术的基础。分组密码以其速度快、易于标准化和和便于软硬件实现等特点成为信息与网络安全中实现数据加密、数字签名、认证及密钥管理的核心体制。随着AES活动的开展,分组密码成为近几年密码学研究中非常活跃的一个课题。自主性是信息安全的一个重要特点,依靠自己的力量并汲取现有的先进经验进行分组密码的研究、设计和开发显得非常必要。在分析了各种混沌分组密码和基于混沌映射设计S盒的基本原理的基础上,针对传统的基于混沌映射构造S盒的方法具有较大随机性、较难搜索到具有良好密码学特性的S盒的缺点,根据混沌映射的特点和密码学特性要求构造了基于混沌的变异算子和适应函数,并提出了基于混沌遗传算法构造S盒的算法。算法首先利用混沌映射生成初始种群,然后对初始种群采用遗传算法中的选择,交叉,变异等操作,其中变异操作采用离散Baker混沌映射对其置乱的方法。仿真实验进一步表明,此方法设计的S盒满足较好的密码学特性,如双射性,高非线性度,严格雪崩效应,输出位独立,等概率异或分布等等,保证了所设计的S盒能够有效地抵抗多种攻击。此方法具有很好的可扩展性,通过改变混沌映射还可以找到其他满足密码特性好的S盒。根据现存的分组密码的各类结构的优缺点,采用Feistel结构设计了混沌分组密码系统。并对此混沌分组密码进行了密码学特性分析,实验证明此密码系统具有较好的密码学特性。通过一个加密数据库系统,来详细说明如何将混沌分组密码应用到实际中。采用J2EE平台实现加密数据库系统,增强了数据库系统的保密性。更多还原

【Abstract】 With the rapid development and extensive applications of information and communication technology, the security and protection of network information are becoming increasingly a key problem that must be solved urgently. Block cipher has many attractive features so that they are usually core components in information and Internet security for data encryption, data signature, authentication, and so on. Along with the launch of AES process, block cipher has become a very active subject in recent years. Autonomy is a notable feature of information security. Thus, it’s very necessary to conduct block cipher research, design and development relying on our own ability.The basic principles of various chaotic ciphers based on the chaotic map and methods for designing S-boxes are analyzed in this paper at first. According to the shortcomings that the traditional methods for designing S-boxes by using chaotic maps can not find good S-boxes easily, this paper proposed a method for designing S-boxes by genetic algorithm based on the chaotic map, which design the fitness function and mutation operator on the basis of characteristics of cryptology. The method is composed of two steps. The first step is generating some S-boxes by using a chaotic map, by this way; an initial data pool can be obtained. Secondly, selection crossover and mutation would be operated on the initial data pool. The mutation is applying a Bake map several times to shuffle the table nonlinearly. In addition, the cryptographic properties such as the bijective property, the strict avalanche criterion, the nonlinearity, the output bits independence criterion and the equiprobable input/output XOR distribution are analyzed in detail for the S-box produced by the method which the paper proposed. The results of numerical analysis show that the S-box has approximately fulfilled the criteria for a cryptographically strong S-box and can resist several attacks, effectively. Based on careful analysis on the properties of the structure of various block cipher, a method combining the chaotic system and the Feistel structure is proposed to design chaotic block cipher, and the performance of this cipher is analyzed in details and is proved to have good performance of cryptology.Finally, a new database encryption scheme based on J2EE platform is discussed and implemented. The result shows that the idea of the encryption is feasible.更多还原