Design And Research Of Several Chaotic Encryption Algorithms

Nonlinear science is a foundational discipline which conceI'nS the common properties of nonlinear phenomena. Particularly, chaos theory is one of important subdisciplines of nonlinear science. The research has studied the relative problems of chaotic cryptography using the method of numerical simulation. The main contents are as follows:A new and efficient image encryption approach based on two high dimensional chaotic maps is proposed. The scheme used a selective way to utilize Lorenz system and Chen system to encrypt the plain-image. Theoretical analyses and computer simulations both confirm that the proposed image encryption scheme provides an efficient and secure way for real-time image encryption and transmission.An algorithm for hash function construction based on chaos system is proposed. By combining floating point computation of chaos and some simple algebraic operations, the system reaches very high bit confusion and diffusion rates, and this enables the system to have desired statistical properties and strong collision resistance. Theoretical analysis and computer simulation have been done to certify that:all performance requirements of hash function can be fulfilled in an efficient and flexible way with this algorithm. And also some secure tests just like birthday attacks and meet-in-the-middle attacks have been done to show that this function is good choice for data integrity or authentication.A fast image encryption and authentication scheme is proposed. In particular, a keyed hash function is introduced to generate a 128-bit hash value from both the plain-image and the secret hash keys. The hash value plays the role of the key for encryption and decryption while the secret hash keys are used to authenticate the decrypted image. Simulation results show that satisfactory security performance is achieved in only one overall round. The speed efficiency is thus improved.