An Audio Covert Communication System for Anolog Channels

This paper designs an audio covert communication system based on spread spectrum (SS) data hiding technology. Considering the characteristics of covert communication, some methods were proposed to solve the key problems in the system. Firstly, the system employed M-ary SS coding combining with return-to-zero base band code to embed hiding data. In addition, the sender embedded the base band clock in audio signal for synchronization. Furthermore, Reed Solomon (RS) channel coding was applied in the system for error correction. This system was tested through an audio line and a FM audio broadcast platform as communication channels. Experiment results showed that the data error rates were 0.024% via audio line and 0.288% via FM audio when the hiding data rate was 7.8 bytes/s.