The Analysis And Improvement Of IDEA Cryptosystem

With the continuous development of network, it joined in our life by various forms. For example, more and more goods have bought from the internet, more and more people begin to use web TV instead of the traditional ones, and more and more people communicate through the network, and so on. In a word, with the increasing of data on the internet day by day, there are more and more attackers and the privacy of people are nearly under the danger. So, many people pay attention to the security of information in the network. At last, the technology about information security becomes a hot topic today.But how to ensure the security of information in the specific network becomes an important question. This means it must consider the question with comprehensive idea. First, when be added to the network, it must regist, which is the certification issues; second, either communicate to another person or machine, it is a problem to communicate, then it need to consider the certification between the communication sides, which named digital signature; at last, after connecting to each other, it must ensure the security of information in the circulation process, which is the information encryption issues. In this text, it focused on the information encryption and decryption algorithm.In this paper, it studied in an encryption algorithm, Block Cipher-IDEA. It can be detailed as follows:(1)First, it gave a brief introduction to the study of the background, current research, purpose and significance of this text. Then it introduced the basic knowledge of this paper, including cryptography and block cipher. And gave DES, AES, and IDEA for example to describe the basic principle of block cipher;(2)It gave a differential-linear attack on 5.5-IDEA based on the identification of 2.5-IDEA. And gave a related-key attack on 8-IDEA. These two attacks of IDEA marked the attack on IDEA getting to another further step.(3)According to the attack on IDEA, this text gave an improved encryption and decryption algorithm and an improved compression key generation algorithm of IDEA. The new encryption algotithm can resist the differential-linear and the related-key attacks. The sub-key algorithm gives the keys abandons the linear relationship between the sub-keys.This article described IDEA for its'attack and improvement. For attack, it gave two kinds of attack. For improvement, it combined with an improved encryption and decryption algorithm and an improved compression key generation algorithm.