A Covert Digital Communication System Using Skewed α-Stable Distributions for Internet of Things

Information security is a key issue involved in the utilization of different technological innovations, such as the Internet of Things (IoT). This study proposes a new covert communication scheme in which the transmitted waveform modulated by the covert bit is statistically similar to the background noise to achieve information security. The impulsive noise in many communication fields can be well modeled with a symmetrical α -stable distribution. Thus, the proposed scheme exploits skewed α -stable distributions to conduct the covert bit. The polarity transition of the skewness parameter within the first and second halves of a bit period represents a covert bit. The resultant signal exhibits a near-symmetrical behavior similar to ambient interference to achieve concealment. The sample skewness estimator based on the signed fractional lower order moment is used to determine the binary message at the receiver. Then, the expression of the skewness estimator and its probability density function are derived. With the aid of the hard decision, the theoretical expression of the bit error rate of the proposed communication system is obtained. The proposed scheme works at the physical layer with the advantages of simple structure, easy implementation, and extreme suitability with low-cost, resource-limited IoT devices exhibiting low-rate transmission.