Hiding Information Into Voice-Over-IP Streams Using Adaptive Bitrate Modulation

Information hiding based on bitrate switching is a novel steganographic scheme for voice over IP, which can resist traditional steganalysis methods. However, the state-of-the-art method has not achieved its best embedding performance. Thus, in this letter, we present two adaptive bitrate modulatingbased steganographic methods introducing Hamming matrix encoding (HME) strategy. The first one can conceal [log2(n + 1)] bits of secret data into n speech frames with at most one bitrate switching by applying the HME strategy to each frame group, while the second one, compared with the state-of-the-art method, can embed (1 + [log2(n + 1)])/2 bits of secret data into n speech frames without increasing the number of bitrate switches by only employing the HME strategy for the frame groups with bitrate switching. The theoretical analysis and experimental evaluation demonstrate that the proposed methods are feasible, and outperform the existing one on both covert bandwidth and embedding efficiency while achieving the comparably good steganographic transparency.