Research On Chaos Encryption Algorithms And Message Authentication Codes

With the rapid development of computer technology, it becomes very convenient to store and duplicate digital information. Moreover, great progress made in telecom-munication technology also helps to spread application of digital information in a wider area. However, security issues in transmissions of digital information through internet or wireless network occur frequently. Cryptology theoretic is the foundation of information security. Chaos encryption based on nonlinear science becomes a hot topic in cryptology research in the past two decades since specific properties in chaotic dynamic systems are similar to traditional cipher. A number of chaos-based encryption schemes are proposed recently, which promote the development of chaos cryptology.This thesis focuses on design of digital chaos encryption algorithm and message authentication code scheme based on chaos. Our main contributions are as follows:1. A stream color image cryptography has been proposed based on spatiotemporal chaos system and multiple chaotic maps. One-way coupled map lattices (OCML) are used to generate pseudorandom sequences and then encrypt image pixels one by one. By iterating randomly chosen chaotic maps from a set of chaotic maps, the generated pseudorandom sequences obtain high initial-value sensitivity and good randomness. Simulation results show that the proposed scheme is efficient and useful for the security of communication system.2. An image encryption scheme based on external secret key is analyzed. Some su-perfluous operations and secure problems are pointed out. And then, an improved color image encryption is proposed, which is based on a chaotic logistic map and a one-way coupled map lattices model. The results of several experimental prove the security robustness of the proposed cryptosystem.3. Security of a scheme based on dynamic sequences of multiple chaotic systems is discussed. We found that this scheme cannot resist chosen plaintext attack, cho-sen ciphertext attack and known plaintext attack. Through some modifications, a securer cipher scheme is proposed that can resist the above three attacks with the same computation efficiency.4. A forward-secure aggregate message authentication code scheme is proposed. In view of the limited space and communication facility of wireless sensor networks, message authentication codes are aggreated. Furthermore, forward security can ensure that all previously generated MAC tags can be still considered to be valid even after the sensor is compromised. An algorithm for parallel keyed hash function construction based on chaotic maps is also introduced.