LEADER 00000nam  2200373   4500 
001    AAINQ77124 
005    20050908073016.5 
008    050908s2002                        eng d 
020    0612771245 
035    (UnM)AAINQ77124 
040    UnM|cUnM 
100 1  Yao, Weiguang 
245 10 Improving security communication via chaotic 
300    147 p 
500    Source: Dissertation Abstracts International, Volume: 64-
       02, Section: B, page: 0758 
500    Advisers: Chris Essex; Pei Yu 
502    Thesis (Ph.D.)--The University of Western Ontario (Canada),
520    Chaos produces a random-like wideband signal sensitive to 
       initial conditions. When a chaotic signal is used as a 
       "carrier" to send a message, the message is not only 
       carried, but also "masked" by the carrier. The message may
       be recovered perfectly at a receiver that is synchronized 
       with the transmitter by using the received signal. This 
       method, called chaotic encryption, is an alternative way 
       for secure communication 
520    Some cracking methods, however, have been designed to show
       that such a communication may not be secure enough if the 
       transmitter carrier is generated by simple forms of chaos.
       One way for improving the security of chaotic encryption 
       is to construct a chaotic system which generates more 
       complicated signals. Another way is to design chaotic 
       synchronization approaches to increase the randomness of 
       the carrier even if the carrier is from a less complicated
       chaotic system 
520    A chaotic synchronization approach is designed. Here, two 
       identical chaotic systems can be synchronized by long 
       interval impulsive chaotic signals. The recovered message 
       is error-free even though a little large noise is added 
       into the systems. The security of the communication is 
       much higher than that using continuous chaotic signals 
       because the randomness of the carrier is greatly increased
       and it is very difficult to reconstruct an attractor from 
       the carrier 
520    A generalized competitive mode (GCM) approach is 
       developed. The idea of the approach is that chaos is the 
       result of a form of mode competition. The necessary 
       condition for a system to be chaotic is that there are at 
       least two such GCM's in the system. By using the necessary
       condition, the chaotic parameter regimes in several 
       chaotic systems are estimated. Further, it is found that 
       the number and the form of GCM's will affect the 
       complexity of chaos. Therefore, one can construct new 
       chaotic systems with pre-designed GCM's. Several new 
       chaotic systems are created. Some iii of them produce very
       complex chaotic motions. The nonlinear dynamical 
       forecasting (NDF) technique, perhaps the most complicated 
       and powerful cracking method, is employed to show that the
       security of the communication via these systems is much 
       improved compared to some well-known chaotic systems. Thus,
       the work may make it possible to develop devices for 
       reasonably secure and practical communication in industry.
       (Abstract shortened by UMI.) 
590    School code: 0784 
590    DDC 
650  4 Mathematics 
650  4 Engineering, Electronics and Electrical 
690    0405 
690    0544 
710 20 The University of Western Ontario (Canada) 
773 0  |tDissertation Abstracts International|g64-02B 
856 40 |uhttp://pqdd.sinica.edu.tw/twdaoapp/servlet/