Steganography in Inactive Frames of VoIP Streams Encoded by Source Codec

Abstract

This paper describes a novel high capacity steganography algorithm for embedding data in the inactive frames of low bit rate audio streams encoded by G.723.1 source codec, which is used extensively in Voice over Internet Protocol (VoIP). This study reveals that, contrary to existing thoughts, the inactive frames of VoIP streams are more suitable for data embedding than the active frames of the streams, that is, steganography in the inactive audio frames attains a larger data embedding capacity than that in the active audio frames under the same imperceptibility. By analysing the concealment of steganography in the inactive frames of low bit rate audio streams encoded by G.723.1 codec with 6.3kbps, the authors propose a new algorithm for steganography in different speech parameters of the inactive frames. Performance evaluation shows embedding data in various speech parameters led to different levels of concealment. An improved voice activity detection algorithm is suggested for detecting inactive audio frames taking into packet loss account. Experimental results show our proposed steganography algorithm not only achieved perfect imperceptibility but also gained a high data embedding rate up to 101 bits/frame, indicating that the data embedding capacity of the proposed algorithm is very much larger than those of previously suggested algorithms.

Using transcoding for hidden communication in IP telephony

“…The DSNR is defined after Huang et al [16] as the difference in SNR between the original speech (without steganography) and when the TranSteg was applied to VoIP call. After the synchronization of two hosts: A and B (Fig.…”

“…Such an approach proved to give better results in terms of voice quality than the LSB-based method. A highcapacity steganography technique based on the utilisation of inactive frames of G.723.1 speech codec was introduced by Huang et al, [16]. The authors prove that the inactive frames of VoIP streams are more suitable for data embedding than the active ones, thus more hidden data can be embedded in them with the same imperceptibility.…”

Comparative study of digital audio steganography techniques

“…The audio signal samples with absolute amplitudes vary from 0 to i are utilized in the hiding process. For a greater hiding capacity, [44] suggested to embed data in the inactive frames of low bit-rate audio streams (i.e., 6.3 kbps) encoded by G.723.1 source codec.…”

On Tuning the Knobs of Distribution-Based Methods for Detecting VoIP Covert Channels

“…This class of channels is known to be practical for use, because of the high bandwidth provided by the channels. However, Huang et al [16] present a VoIP covert channel using steganography that claims to have a high capacity. Methods for detecting covert channels include those based on entropy [13] (but these are specifically only applicable to timing-based channels) and n-gram statistical analysis [10].…”