Analysis And Design Of Block Ciphers

Modem cryptological theory and cryptological technology are important basis of information security. Block cipher is an important branch of cryptology, it has many attractive features such as high rates, easy for standardization, and efficient for both software and hardware implementations. Block ciphers are usually core components in information and Internet security for data encryption, data signature, authentication and key management.Along with the launch of AES process, block ciphers has become a very active subject in recent years. Autonomy is a notable feature of information security. So it's very necessary to conduct block cipher research, design and development relying on our own ability, and absorbing advanced experience at the same time.The research contents of block ciphers can be divided into three parts: design principles of block ciphers, security analysis of block ciphers and application research of block ciphers. Concentrating on security analysis and design of block ciphers, five principal achievements have been obtained in this dissertation:1.Using differential-nonlinear cryptanalysis, truncated differential-linear cryptanalysis and integral cryptanalysis respectively, three attacks of reduced-round Safer++ are given;2.Based on the survey of provable security and practical security of block ciphers, a block cipher model of SPN cipher containing Feistel structure is proposed. Adopting this model and properly selecting some nonlinear and linear modules which has good cryptographic properties, a concrete block cipher can thus be constructed, which is provably secure against differential and linear cryptanalysis, and also has self-inverse structure for encryption and decryption.3.Adopting the above model, a concrete block cipher named SCF is proposed. Some initial cryptanalysis and detailed statistical tests of SCF are given, the results show that SCF can resist some known cryptanalytic attacks and has excellent statistical properties.4.Security of a class of block ciphers based on chaotic maps against differential and linear cryptanalysis is studied. The results show that this kind of cipher structure is not good compared with some famous cipher structure such asCAST-256 cipher structure and common Feistel structure. So we don't recommend this kind of cipher structure when designing a new cipher. 5. Security analyses of a variant of a new block cipher system (called CAC) based on cellular automata theory are given using two cryptanalytic approaches. The results show that this variant of CAC is very insecure under chosen-plaintext attacks. The importance of analysis of this variant is: using cryptanalysis of the variant for reference, attacks on the original cipher may be found when knowing some of the design details of CAC.