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 thought, 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 analyzing the concealment of steganography in the inactive frames of low bit rate audio streams encoded by G.723.1 codec with 6.3 kb/s, 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.

/pdf/steganography-in-inactive-frames-of-voip-streams-encoded-by-1harygnlpp.pdf

Steganography in Inactive Frames of VoIP Streams Encoded by Source Codec

Low bit-rate speech codecs have been widely used in audio communications like VoIP and mobile communications, so that steganography in low bit-rate audio streams would have broad applications in practice. In this paper, the authors propose a new algorithm for steganography in low bit-rate VoIP audio streams by integrating information hiding into the process of speech encoding. The proposed algorithm performs data embedding while pitch period prediction is conducted during low bit-rate speech encoding, thus maintaining synchronization between information hiding and speech encoding. The steganography algorithm can achieve high quality of speech and prevent detection of steganalysis, but also has great compatibility with a standard low bit-rate speech codec without causing further delay by data embedding and extraction. Testing shows, with the proposed algorithm, the data embedding rate of the secret message can attain 4 bits/frame (133.3 bits/second).

/pdf/steganography-integration-into-a-low-bit-rate-speech-codec-10nmlefyla.pdf

Steganography Integration Into a Low-Bit Rate Speech Codec

Steganography is an ancient art that encompasses various techniques of information hiding, the aim of which is to embed secret information into a carrier message. Steganographic methods are usually aimed at hiding the very existence of the communication. Due to the rise in popularity of IP telephony, together with the large volume of data and variety of protocols involved, it is currently attracting the attention of the research community as a perfect carrier for steganographic purposes. This article is a first survey of the existing Voice over IP (VoIP) steganography methods and their countermeasures.

http://romisatriawahono.net/lecture/rm/survey/computer%20vision/Mazurczyk%20-%20VoIP%20Steganography%20and%20Its%20Detection%20-%202014.pdf

VoIP steganography and its Detection—A survey

The paper presents a new steganographic method for IP telephony called TranSteg (Transcoding Steganography). Typically, in steganographic communication it is advised for covert data to be compressed in order to limit its size. In TranSteg it is the overt data that is compressed to make space for the steganogram. The main innovation of TranSteg is to, for a chosen voice stream, find a codec that will result in a similar voice quality but smaller voice payload size than the originally selected. Then, the voice stream is transcoded. At this step the original voice payload size is intentionally unaltered and the change of the codec is not indicated. Instead, after placing the transcoded voice payload, the remaining free space is filled with hidden data. TranSteg proof of concept implementation was designed and developed. The obtained experimental results are enclosed in this paper. They prove that the proposed method is feasible and offers a high steganographic bandwidth while introducing small voice degradation. Moreover, TranSteg detection is difficult to perform when compared with existing VoIP steganography methods.

/pdf/using-transcoding-for-hidden-communication-in-ip-telephony-aha5n9cndu.pdf

Using transcoding for hidden communication in IP telephony

Steganography is an ancient art that encompasses various techniques of information hiding, the aim of which is to secret information into a carrier message. Steganographic methods are usually aimed at hiding the very existence of the communication. Due to the rise in popularity of IP telephony, together with the large volume of data and variety of protocols involved, it is currently attracting the attention of the research community as a perfect carrier for steganographic purposes. This paper is a survey of the existing VoIP steganography (steganophony) methods and their countermeasures.

VoIP Steganography and Its Detection - A Survey

In this paper we introduce a novel codebook partition algorithm for quantization index modulation (QIM), which is applied to information hiding in instant low bit-rate speech stream. The QIM method divides the codebook into two parts, each representing '0' and '1' respectively. Instead of randomly partitioning the codebook, the relationship between codewords is considered. The proposed algorithm - complementary neighbor vertices (CNV) guarantees that every codeword is in the opposite part to its nearest neighbor, and the distortion is limited by a bound. The feasibility of CNV is proved with graph theory. Moreover, in our work the secret message is embedded in the field of vector quantization index of LPC coefficients, getting the benefit that the distortion due to QIM is lightened adaptively by the rest of the encoding procedure. Experiments on iLBC and G.723.1 verify the effectiveness of the proposed method. Both objective and subjective assessments show the proposed method only slightly decreases the speech quality to an indistinguishable degree. The hiding capacity is no less than 100 bps. To the best of our knowledge, this is the first work adopting graph theory to improve the codebook partition while using QIM in low bit-rate streaming media.

An Approach to Information Hiding in Low Bit-Rate Speech Stream

With the development of Internet and multimedia technology, the information exchanged through Internet not only must be real-time, but also requires security and integrity. In this paper, a SIP (Session Initiation Protocol) UA (User Agent) that can dynamically embed some secret message into the speech carrier with good efficiency is implemented. The principle of the secret communication based on steganography technology over VoIP is introduced, and a new architecture of the software used to transmit the hidden information is proposed. Especially, we adopt a relatively new steganography algorithm, which is referred to as LSB matching method. In addition, an approach for avoiding the loss of secret data based on Redundant Audio Data is presented. Finally, we analyzed the performance of the implemented software.

Implementation of Covert Communication Based on Steganography

Covert channels are used to secretly transfer information. Due to the widely existence of network protocols, encoding covert channels into computer network protocols is highly applicable. The jitter field of RTCP header possesses a characteristic that could be used to set up covert channels. Thus, in this paper, a novel covert channel on jitter field is proposed. In order to set up this channel, statistical parameters of the jitter field in the current network are calculated. Then the secret message is modulated into the jitter field according to the parameters obtained. Because of this modulation method, the characteristic of the covert channel is similar to that of the overt channel. We analyzed the natural variation of jitter data and verified the proposed channel. The test result shows that the attacker could not detect the covert channel by its statistical parameters.

Yongfeng Huang

Papers

An Approach to Information Hiding in Low Bit-Rate Speech Stream

Implementation of Covert Communication Based on Steganography

Covert Channels Based on Jitter Field of the RTCP Header