Real-Time Scheme for Covert Communication Based VoIP

Covert communication is an important necessity for governments and companies due to the ease of eavesdropping and access to information. A private channel with robust encryption can provide the required protection for the communications. However, a public channel is cheaper and less restrictive (from any place and any communication devices) than private channels. This paper proposes a real-time covert communication scheme by creating a secret speech channel in a public speech channel based on audio steganography. The scheme compresses the secret speech using a very fast and simple process based on lifting wavelet transform. Also, the cover speech is compressed by G.711 encoder at synchronous time periods with respect to the secret speech to meet the networks of voice over internet protocol (VoIP). Subsequently, the secret data hides in a compressed cover speech data in real-time. The embedding procedure employs the only high strength data for embedding to maintain the quality of the cover data after embedding at greater than 40 dB in terms of signal to noise ratio (SNR). The secret data is retrieved 100% without error in case of a lossless channel.