Research On Block Cryptography With Variable Structure And Its Application

The research is from Fujian provincial natural science fund subject: "Computer & Communication Network Variable Structure Data Encryption and Security Research". With the rapid development of information and communication technology, people attach more importance to the information & correspondence security, especially to network security. The dissertation research mainly block cryptography and its application, which is based on variable structure. The approach has definite theoretical significance, and has better practical values for information, communication and network security. Cryptography technology is the core of information security, and block cipher is one of most important research in cryptography, its security, which protect data storage and transmission, can't be replaced by other types of ciphers. The born of AES and the launching of NESSIE project, bring a new climax of block cipher research all over the world. So, the thesis studies and discusses the subject deeply at this research background.First, the thesis introduces summarily the status quo of block cipher, and analyzes its development trend. Second, it approaches the main theory and technology of block cipher, and analyzes some important block ciphers such as DES & AES(Rijndael). And then, it based on the above discussion, discard the dross and select the essential, according to the AES' design criteria, proceed from the aspect of variable structure of core part of block cipher encryption, the thesis improves and designs two kind of block cipher algorithm models with variable structure. The first kind of algorithm is based on S-box controlled by key, the algorithm distinguishes most of other block ciphers, its visible quality is that its S-box is not regular and fixative, but controlled by block cipher's key. The second kind of algorithm is based on SMn(D) array code, it makes full use of the visible quality of SMn(D) array code possessing big code distance(D). The thesis discusses the two algorithms' reversibility, security and their qualities, theconclusion is that the two algorithms with variable structure are correct, efficient and secure.The first chapter introduces status quo and trend of block cryptography; the second chapter analyzes primary design philosophy of block cipher in detail; the third chapter studies and analyzes DES & AES algorithm(Rijndael); the fourth chapter approach the technology of implementation of block cipher from the aspect of hardware realization; the fifth and sixth chapters are the focus of this research subject, it researches respectively two kind of variable structure block cipher, one of algorithms is based on S-box controlled by key, and another is based on SMn(D) array code.