Experimental evidence of detecting hidden frequency in chaos communications
In chaos communications, security is based on the complex dynamic behaviors provided by chaotic systems. The basic idea of chaos-based communications is that the information signal to be transmitted is mapped by synchronizing the transmitted and the local generated chaotic signal at the receiver. In this work, we introduce a methodology to obtain the hidden frequencies (information) in a dynamical system by utilizing a second variable frequency (fixed amplitude) in the dynamical system. By this technique, it is possible, through a spectral analysis to apply a variable frequency over the dens chaotic time series. Experiments show that the oscillator is sensitive to the small signal having the little frequency difference with the referential (embedded) signal and immune against the random frequency.
On the other hand, the modeling results show through analyzing the modulated chaos of laser with optical feedback; we found that the system output is an intermittent chaotic signal when input frequency deviates the compulsory drive frequency slightly. The deviation can be estimated by the statistical characteristic of output chaotic signal.
This method can be used to extract the hidden frequency in a chaotic environment without synchronization process; this could open a novel way in chaos communications