Design And Research Of Several Chaotic Cryptosystems

Chaos is an important subdiscipline of nonlinear science. Cryptology is an important field of information security. Chaotic cryptology is a subject related to both chaos and cryptology. It is a new subdiscipline of cryptology. This paper researches chaotic cryptology, proposes and analyzes some new chaotic cryptosystems. The main contents of this paper are as follows:A new symmetric chaotic cryptosystem based on multiple one-dimensional chaotic maps is proposed. The proposed cryptosystem uses a table which stores the relations between the chaotic maps and encryption tasks to achieve dynamic combination of chaotic maps and encryption tasks. Meanwhile, the cryptosystem uses pseudorandom properties and secret key sensitivity of the multiple chaotic maps to achieve desirable diffusion and confusion properties which insure the security of the plaintext.A multiple-plaintext-oriented chaotic cryptosystem is proposed. The cryptosystem is dedicated to the application of encrypting a batch of plaintexts. In this cryptosystem, dependences are established among these multiple plaintexts, which make the plaintexts and ciphertexts affect each others. This algorithm can effectively prevent the attackers from attacking these plaintexts one by one. Moreover, the proposed cryptosystem uses the desirable dynamic properties of multiple chaotic maps to further enhance the security of the plaintexts.A chaotic stream cryptosystem based on piecewise linear chaotic maps and coupled map lattices is proposed. This cryptosystem make use of the advantages of piecewise linear chaotic maps and coupled map lattices. Moreover, we use M-sequence to disturb the trajectories of the chaotic maps to avoid the problems caused by dynamical degradation of chaotic systems. The proposed cryptosystem can generate pseudo-randam sequence effectively and use it to encrypt plaintext.An existent chaotic cryptosystem is analyzed. We find out the security flaws of this cryptosystem and proposed an effective method to attack it. A remedial improvement scheme is also proposed to improve the cryptosystem to make it resistant to the proposed attack, and enhance its security without affecting its efficiency.