Research And Implementation Of Cascade Ciphers

The Block Cipher is characterized as high safety, super-speed. It is very easy to implement by software or hardware. It is a very important way to encrypt data of information and safety of network. Also it is widely used particularly in telecommunication; bank; stock-certificate, etc. But along with the appear of every kind of new technique of cryptanalysis (such as Differential Cryptanalysis, linear Cryptanalysis), the Block Cipher suffers the serious threat. Particularly with the progress of computer and Internet, it is slowly feasible to crack ciphers by exhaustive experiments. In order to improve the safety using current ciphers, Cryptologists bring up the thought of enhancing of Block Cipher. The way to enhancing of Block Cipher primarily have: Cascade cipher(CC); multiple cipher; whitening etc.This thesis designs a method of cascade cipher, and designs and realizes a kind of cascade cipher to encrypt files. The thesis introduces the mechanism and development of Block Cipher first, and then puts great emphasis to introduce the system of CC. CC is point to use the arithmetic A to encrypt a news with K_A, then use the arithmetic B to encrypt with K_B, among them the arithmetic can be expanded to many. The research of CC suggested, if all of keys are mutually independent, the intension of CC follows at least the first arithmetic. More clear and definite is: Usage of chosen-plaintext attack, the CC is at least as difficult as its single cipher to be decrypted. The cascade cipher of two stage can be cracked by meet-in-the-middle attack. In this thesis, we use some methods to avoid this attack. It is also analyzed and compared with other technology.The system primarily has three great models: user interface, generation of key, encryption, and it is realized by JCE. We respectively analyze the principle, design and implementation of three models. According to the special functions, the thesis also introduces with key generation, realization of cascade cipher and how to encrypt (decrypt) files.