A new scheme for covert communication via 3G encoded speech

Mobile communication through 3G network has grown rapidly in recent years. It might be of interest to transmit secret messages over 3G voice channels. In this paper, we introduce a new covert communication scheme via Adaptive Multi-Rate Wideband (AMR-WB) encoded speech. An adaptive suboptimal pulse combination constrained (ASOPCC) method is presented to embed data on compressed speech signal of AMR-WB codec. The method takes advantage of the “redundancy”, created by non-exhaustive search of algebraic codebook, to encode secret information. An embedding factor η is used to control embedding bits. By properly setting η, ASOPCC can offer a better trade-off between speech quality and embedding capacity in the process of coding mode switching. Experimental results show that the proposed method is quite promising for both high capacity and good imperceptivity. Although ASOPCC is only applied to AMR-WB codec in this article, it can be further used by any other speech coding based on Algebraic Coded Exited Linear Prediction (ACELP).

Secret messages can be hidden into fixed codebook parameters by using ASOPCC-based steganographic search procedure. The procedure aims to search a suboptimal codevector which matches a constraint condition. The selected suboptimal codevector carries the secret messages. So it is also called stego-codevector.Figure optionsDownload as PowerPoint slideHighlights
► A novel steganography method on 3G encoded speech is proposed.
► Secret messages are encoded by searching suboptimal pulse combination.
► A well balance between speech quality and embedding capacity is got by adjusting embedding factor η.
► Embedding rate (1600–3200 kbps) is superior to related schemes.
► The method generates less abnormal statistics and is difficult to detect.