The application of Advanced Encryption Standard toChaotic Synchronization Systems: Using Improved GeneticAlgorithm as Auxiliary

• Main Authors: Guang-Wei Liou, 劉廣尉
• Other Authors: Feng-Hsiag Hsiao
• Format: Others
• Language: en_US
• Published: 2014
• Online Access: http://ndltd.ncl.edu.tw/handle/k5unan

碩士 === 國立臺南大學 === 電機工程學系碩博士班 === 102 === This study proposed a method of an improved genetic algorithm (IGA)-based secure communications in multiple time-delay chaotic (MTDC) systems with optimal H∞ performance and advanced encryption standard (AES). Chaotic synchronization may be affected when a hacker steals the information to estimate or demodulate it via the public channel. Different methods have been developed to hide the message contents using chaotic signals. However, those methods have been found to be in secure or have a low security. Therefore, this study attempts to combine chaotic synchronization with AES algorithm to increase the complexity of the cryptosystem. The proposed method can obtain a more secure communication system, while effectively protecting the encrypted message. First, an initial round key is applied via AES encryption function to acquire the encrypted message. The encrypted message is used to carry out double encryption by chaotic synchronization. A robust fuzzy observer design is then presented to address the effects of modeling errors between the MTDC systems and Takagi-Sugeno (T-S) fuzzy models. Next, in terms of Lyapunov's direct method, a delay-dependent exponential stability criterion is derived to guarantee that the trajectories of the slave system can approach those of the master system. Subsequently, the stability conditions of this criterion are transformed into linear matrix inequalities (LMIs). In addition, the genetic algorithm (GA) has drawn great attention from researchers due to the capability of the GA in random search to find near-optimal solutions. The lower and upper bounds of the search space based on the LMI approach can be set so that the GA will seek better feedback gains for fuzzy observers, thus accelerating the synchronization. However, the GA has the shortcomings of premature convergence and local search. Therefore, an IGA is proposed in this study to effectively overcome the weakness of the traditional GA. On the basis of the IGA, a fuzzy observer is synthesized to realize the exponential synchronization and achieve optimal H∞ performance by minimizing the disturbance attenuation level. Finally, a numerical example with simulations is given to demonstrate the effectiveness of our approach.