IDEA子密钥扩展算法及其与MD5混合加密算法的研究

发布时间：2018-07-16 23:46

【摘要】：从公元前2000年至今,作为信息安全重要领域之一的学科,密码学研究一直都未停止过,其在战争、军事等方面发挥不可替代的作用,有重要的研究意义。但因为计算机处理速度加快,密码破译方面的研究也飞速发展,导致到目前为止安全可行的密码算法少之又少,国家标准的密码体制更是寥寥无几。本文围绕两种现有的加密算法:IDEA(International Data Encryption Algorithm,IDEA)和MD5(Message-digest Algorithm 5,MD5)遇到的不安全挑战展开研究。本文的研究工作主要包含以下几个方面:第一,阐述密码学的课题发展历史、研究背景及研究意义,着重对密码学发展历史及其分类进行阐述。重点研究IDEA、MD5密码体制的实现过程,包含加密过程、密钥扩展算法、解密过程及算法安全性。第二,针对IDEA弱密钥问题提出一种改进的子密钥扩展算法。首先通过对一组128位初始密钥位进行随机散列;然后根据得到的随机散列值利用同义词链地址法生成若干个无线性关系的子密钥,重复以上步骤直至生成52个子密钥。对照原来的IDEA子密钥扩展算法,解决了原子密钥扩展算法的差分-线性分析及相关子密钥攻击对IDEA算法造成的挑战,保证了IDEA密码算法的安全性。并且在程序实现可接受的效率范围内实现此算法。实验证明,该算法解决了IDEA密码算法的弱密钥问题,且在效率方面比往期改进后的子密钥扩展算法明显提高。第三,针对MD5不安全及IDEA大明文下大密文空间的问题提出一种新的基于MD5和改进后的IDEA混合加密算法。首先将明文作为输入MD5算法的输入,通过MD5算法加密完成后输出密文;然后将输出的密文作为改进后IDEA密码算法的输入,根据改进后IDEA对其进行加密,加密完成后输出固定长度的密文。并且在程序实现可接受的效率范围内实现此算法。实验证明,当明文空间大于256bits时综合考虑算法效率、安全性及存储空间,混合加密算法优势明显。
[Abstract]:Since 2000 BC, as one of the important fields of information security, cryptography research has never stopped. It plays an irreplaceable role in war, military and so on, and has important research significance. However, due to the fast speed of computer processing and the rapid development of cryptographic decoding research, so far, there are very few secure and feasible cryptographic algorithms, and the national standard cryptosystem is even less. This paper focuses on the insecure challenges encountered by two existing encryption algorithms: idea (International data encryption algorithm) and MD5 (Message-digest Algorithm 5MD5). The research work of this paper mainly includes the following aspects: first, the development history, research background and research significance of the subject of cryptography are expounded, and the development history and classification of cryptography are emphasized. This paper focuses on the implementation of IDEAN MD5 cryptosystem, including encryption process, key extension algorithm, decryption process and algorithm security. Secondly, an improved subkey expansion algorithm is proposed for idea weak key problem. Firstly, a set of 128-bit initial key bits are randomly hashed, and then the sub-keys of several wireless relationships are generated by using the synonym chain address method according to the resulting random hash values, and the above steps are repeated until 52 sub-keys are generated. Compared with the original idea subkey expansion algorithm, the difference linear analysis of atomic key expansion algorithm and the challenge caused by related subkey attacks to idea algorithm are solved, and the security of idea cryptographic algorithm is ensured. The algorithm is implemented within the acceptable efficiency range of the program. Experimental results show that the algorithm solves the weak key problem of idea cipher algorithm, and its efficiency is much higher than that of the previous improved sub-key expansion algorithm. Thirdly, a new MD5 and improved idea hybrid encryption algorithm is proposed to solve the problem of MD5 insecurity and large ciphertext space under idea Daming. Firstly, the plaintext is taken as the input of MD5 algorithm, then the ciphertext is output after the encryption is completed by MD5 algorithm, and then the ciphertext output is used as the input of the improved idea cipher algorithm, which is encrypted according to the improved idea. Output a fixed length ciphertext after encryption is complete. The algorithm is implemented within the acceptable efficiency range of the program. The experimental results show that when the plaintext space is larger than 256bits, the hybrid encryption algorithm has the advantage of considering the efficiency, security and storage space of the algorithm.
【学位授予单位】：中北大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TN918.4

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