Applying chaos in secure communications

Recent research in chaos theory now permits engineers to design chaotic systems that exploit the previously undesirable property of randomness. As suggested by many researchers, the random appearance of chaos makes it an ideal candidate for secure communication applications. We will investigate the issues involved in applying analog and digital chaotic systems to secure communications by focusing on parameter estimation, communications through chaotic MEMS and chaotic digital filter synthesis with applications in encryption.; In binary transmission schemes, synchronized chaos relies on the almost perfect match of parameters at the transmitter and receiver. We examine the effects of parameter mismatch and propose four algorithms that estimate the system parameters by observing the transmitter's chaotic output. After the parameters are examined, proper compensation can be applied to ensure the fidelity of the transmitted data.; For the first time, we observed chaotic motions and extracted signals from the micro-electro-mechanical systems (MEMS) with structures having the double well potential as those in the Duffing systems. Parameter estimation and model verification was performed using the experimental data. The complicated nonlinearity in MEMS makes parameter estimation difficult without precise knowledge about the device. A parameter-matched MEMS pair is only likely to occur when the devices with identical parameters are juxtaposed on the same wafer. We also demonstrate that information signals can be sent through matching chaotic MEMS pairs using binary transmission or phase modulation (PM).; Analog systems can not recover signals losslessly. To achieve high fidelity and exploit the high speeds in common digital signal processing, operations in the digital domain are attractive. We develop a synthesis technique for constructing chaotic digital filters and demonstrate an approach to encryption that uses discrete dynamical systems rather than traditional methods that are based on algebra and number theory.; Finally, the possible use of chaos in multiuser communications will be investigated.