RC4流密码算法的研究与改进

发布时间：2018-08-31 13:39

【摘要】：流密码是现代密码学的一个重要分支,RC4流密码高效、易实现,广泛应用于网络安全、数据库安全等领域中。随着互联网迅速发展与应用普及,对网络安全提出了更高的要求。RC4流密码算法的安全性面临着严峻的挑战,成为人们关注的热点问题之一。本文介绍了流密码的相关理论,研究了流密码的工作原理,设计准则。分析了几种典型的对RC4的攻击方案,重点研究了RC4的内部状态、输出过程、设计原则以及攻击方法。针对RC4流密码算法易受弱密钥攻击,区分攻击和错误引入攻击,提出了一种基于随机置换的改进算法—-RC4_n_m,该算法具有以下特点：(1)基于随机置换,对内部状态表进行非线性运算,能够动态的扩展状态表中元素的取值空间,并使得状态表中的元素不断被更新,保证了状态表的可重用性。(2)在密钥编制算法中引入一个秘密数,该秘密数随着状态表的变换而变化,具有更高的安全性。在伪随机序列生成算法中,秘密数参与状态表的变换,确保了状态表的均匀性。(3)RC4_n_m的密钥流序列由状态表的前后两个状态共同决定,增强了密钥流序列的随机性。伪随机序列生成算法每次输出32位远大于RC4输出的8位数,所以RC4_n_m效率优于RC4流密码算法。最后,对RC4_n_m算法正确性,随机性和效率测试。实验结果表明,RC4 n m算法是正确可行的,其密钥流随机性和效率优于RC4流密码算法。
[Abstract]:Stream cipher is an important branch of modern cryptography, RC4 stream cipher is efficient, easy to implement, widely used in network security, database security and other fields. With the rapid development and popularization of the Internet, the security of the. RC4 stream cipher algorithm is facing a severe challenge, which has become one of the hot issues that people pay attention to. This paper introduces the theory of stream cipher, studies the working principle and design criterion of stream cipher. In this paper, several typical attack schemes against RC4 are analyzed, and the internal state, output process, design principles and attack methods of RC4 are studied. In view of the vulnerability of RC4 stream cipher algorithm to weak key attack, distinguish attack and error introduction attack, an improved algorithm based on random permutation, RC4Stack _ n _ m, is proposed. The algorithm has the following characteristics: (1) based on random permutation, The nonlinear operation of the internal state table can dynamically extend the value space of the elements in the state table, and make the elements in the state table constantly updated, which ensures the reusability of the state table. (2) A secret number is introduced into the key compilation algorithm. The secret number changes with the change of the state table and has higher security. In the pseudorandom sequence generation algorithm, the secret number participates in the transformation of the state table, which ensures the uniformity of the state table. (3) the key stream sequence of RC4_n_m is determined by the two states before and after the state table, which enhances the randomness of the key flow sequence. The output of pseudorandom sequence is much larger than the 8-bit output of RC4, so the efficiency of RC4_n_m is better than that of RC4 stream cipher. Finally, the correctness, randomness and efficiency of RC4_n_m algorithm are tested. The experimental results show that the RC4 n-m algorithm is correct and feasible, and the randomness and efficiency of the key stream is better than that of the RC4 stream cipher algorithm.
【学位授予单位】：合肥工业大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TN918.1

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