Research On IDEA Sub Key Expansion Algorithm And Its Hybrid Encryption Algorithm Based On MD5

From 2000 BC to the present,as one of the important areas of information security,cryptography has not stopped,it plays an irreplaceable role in war,military and other aspects.But because of the speed of computer processing,password deciphering research develops rapidly,which resulting in so far safe and feasible password algorithm is very few and the national standard password system is very few.This paper focuses on the insecurity challenges of two existing encryption algorithms:IDEA(International Data Encryption Algorithm,IDEA)and MD5(Message-digest Algorithm 5,MD5).The research work of this paper mainly includes the following aspects:Firstly,the development history,research background and research significance of cryptography are expounded,and the paper focuses on the development history and classification of cryptography and the implementation process of IDEA and MD5 algorithm,including encryption process,key expansion algorithm,decryption process and algorithm security.Secondly,an improved subkey expansion algorithm is proposed for IDEA weak key problem.First,a random hash is performed on a set of 128-bit initial key bits.Then,the sub-keys of several wireless relationships are generated by using the synonym chain address method according to the obtained random hash values.Repeat the above steps until 52 subkeys are generated.The improved key expansion algorithm ensures the IDEA password algorithm security contrast with the original IDEA subkey expansion algorithm.And the paper implements this algorithm within the acceptable efficiency range of the program implementation.Experiments show that the algorithm solves the weak key problem of IDEA cryptography algorithm,and improves the efficiency of subkey expansion algorithm.Thirdly,a new MD5-based and improved IDEA hybrid encryption algorithm is proposed for the problem of MD5 insecurity and large storage space space of IDEA.First,the plaintext is input as the input MD5 algorithm,and the ciphertext is output after the MD5 algorithm is encrypted.Then,the output ciphertext is used as the input of the improved IDEA cipher algorithm,and is encrypted according to the improved IDEA.After the encryption is completed,the fixed length ciphertext is output.The paper implements this algorithm within the acceptable efficiency range of the program implementation.Experiments show that the hybrid encryption algorithm has obvious advantages when the plaintext space is larger than 256 bits.