Steganographic embedding of a secret message in a video flow

The paper presents a steganographic method which hides a secret message in a video flow. The secret message represents the result of a chaos-based encryption scheme. One of the flaws which make the algorithm unpractical for real-time applications is that, while the elements of the plain-message are represented using 8 bits (ASCII characters) the corresponding encrypted values need to be represented using 16 bits. Since the pixels of a typical image are represented using 24 bits (8 bits for each color component), each encrypted character fits in only one pixel. Moreover, since the resolution of today’s video materials is very large, the pixel previously established to carry in its evolution the hidden content will not be obvious to unaware spectators, but only to the one which knows its coordinates. In addition to the steganographic procedure, the work presents preliminary results on the degree of pseudo-randomness of video flows. The study is based upon the idea behind Lyapunov exponents. The evolution of two pixels which initially differ only by the minimum possible value (the color representation’s resolution) is followed for a large number of video frames. The distance between such points, for pseudo-random behavior, is known to evolve over time in a Gaussian manner. A Kolmogorov-Smirnov statistic is computed and illustrated in order to conclude over the provenience of the data series representing the evolution of the distance between the two initially neighboring pixels from a standard normal law.