Self-Embedding Watermarking with Content Restoration Capabilities

In this chapter, the authors give a survey about self-embedding watermarking, which enables not only detection of tampered regions but also recovering the damaged information. They introduce the pioneering method as well as the representative schemes, including adjacent-block detection, hierarchical detection and self-recovery, dual watermarks, reference sharing, and flexible self-recovery. The authors analyze the distinguishing features and loopholes by considering four key techniques, namely the secure block-mapping function, the unambiguous authentication, the reference information extraction, and the watermark embedding approaches. They make comparative studies on the above works and then outline further research directions and a conclusion.

Reversible Information Hiding and Its Application to Image Authentication

This chapter addresses a new class of Reversible Information Hiding (RIH) and its application to verifying the integrity of images. The method of RIH distorts an image once to hide information in the image itself, and it not only extracts embedded information but also recovers the original image from the distorted image. The well-known class of RIH is based on the expansion of prediction error in which a location map, which indicates the pixel block positions of a certain block category, is required to recover the original image. In contrast, the method described in this chapter is free from having to memorize any parameters including location maps. This feature suits the applications of image authentication in which the integrity of extracted information guarantees that of a suspected image. If image-dependent parameters such as location maps are required, the suspected image should first be identified from all possible images. The method described in this chapter reduces such costly processes.

Advanced Information Hiding for G.711 Telephone Speech

G.711 is the most popular speech codec for Voice over IP (VoIP). This chapter proposes a method for embedding data into G.711-coded speech for conveying side information for enhancing speech quality such as bandwidth extension or packet loss concealment. The proposed method refers to a low-bit rate encoder to determine how many bits are embedded into each sample. First, a variable-bit rate data hiding method is proposed as a basic framework of the proposed method. Then, the proposed method is extended to achieve fixed bit rate data hiding. According to comparison experiments, the proposed method is proved to achieve higher speech quality compared with the conventional method. Moreover, the authors developed a low-complexity speech bandwidth extension method that uses the proposed data hiding method.

Data Hiding for Stereo Audio Signals

This chapter proposes two data-hiding algorithms for stereo audio signals. The first algorithm embeds data into a stereo audio signal by adding data-dependent mutual delays to the host stereo audio signal. The second algorithm adds fixed delay echoes with polarities that are data dependent and amplitudes that are adjusted such that the interchannel correlation matches the original signal. The robustness and the quality of the data-embedded audio will be given and compared for both algorithms. Both algorithms were shown to be fairly robust against common distortions, such as added noise, audio coding, and sample rate conversion. The embedded audio quality was shown to be “fair” to “good” for the first algorithm and “good” to “excellent” for the second algorithm, depending on the input source.

Acoustic OFDM Technology and System

This chapter presents a method of aerial acoustic communication in which data is modulated using OFDM (Orthogonal Frequency Division Multiplexing) and embedded in regular audio material without significantly degrading the quality of the original sound. It can provide data transmission of several hundred bps, which is much higher than is possible with other audio data hiding techniques. The proposed method replaces the high frequency band of the audio signal with OFDM carriers, each of which is power-controlled according to the spectrum envelope of the original audio signal. The implemented system enables the transmission of short text messages from loudspeakers to mobile handheld devices at a distance of around 3m. This chapter also provides the subjective assessment results of audio clips embedded with OFDM signals.

Reversible Audio Data Hiding in Spectral and Time Domains

Reversible data hiding is a technique whereby hidden data are embedded in host data in such a way that the host data consistency is perfectly preserved and the host data are restored when extracting the hidden data. This chapter introduces basic algorithms for reversible data hiding, histogram shifting, histogram expansion, and compression. This chapter also proposes and evaluates two reversible data hiding methods, i.e., hiding data in the frequency-domain using integer Discrete Cosine Transform (DCT) and modified DCT and hiding in the time domain using linear prediction and error expansion. As no location map is required to prevent amplitude overflow, the proposed method in the time domain achieves a storage capacity of nearly 1 bit per sample of payload data. The proposed methods are evaluated by the payload amount, objective quality degradation of stego signal, and payload concealment.

Data Hiding for Text and Binary Files

This chapter presents an overview of text-based and binary-based data hiding methods. Text methods, through which secret information is embedded into innocent-looking textual data, are mostly used for steganography. Binary methods are applied to program binary codes: executables and libraries. In binary methods, information is embedded into a binary code so that its functionality is preserved. Data hiding methods for binary codes have been studied intensively to perform watermarking for protecting software from piracy acts. A message can also be embedded into a binary code in a steganographic manner. Another method is also introduced, which is proposed for enhancing the performance of an executable file.

Data Embedding Methods Not Based on Content Modification

Creation of a stego object by embedding information in a cover object often distorts the cover object. As more information is embedded, more annoying noise is introduced in stego objects. Although reversible embedding methods enable us to restore the original cover object even after embedding, stego objects are not free from distortions. Embedding information does not, however, always result in damaging the contents of the cover object. This chapter introduces data embedding methods that are not based on modification of the contents of cover objects: permutation steganography, metadata steganography, and cover generation methods. This chapter focuses on elaborating the basic principles of these techniques.

New Proposals for Data Hiding in Paper Media

Digital watermarks provide the capability to insert additional information onto various media such as still images, movies, and audios, by utilizing features of the media content. Several techniques that use content features such as text or images have already been proposed for printed documents. The authors propose two new techniques using a single dot pattern and an Artificial Fiber (AF) pattern in order to address the disadvantages of conventional information hiding technologies for paper media. In this chapter, the authors describe each scheme’s characteristics, and how to improve its robustness. As a result, they have attained greater than 80% extraction rate with an information hiding capacity of 91 Kbits in the case of the single dot pattern, and a 100% extraction rate with color characters as the foreground in the case of using artificial fiber patterns.

Introduction to Image Steganography and Steganalysis

This chapter reviews information hiding methods, with a focus on steganography and steganalysis. First, the authors summarize image data structures and image formats required by computers and the Internet. They then introduce several information hiding methods based on image formats including lossless (non-compression based), limited color-based image data, JPEG, and JPEG2000. The authors describe a steganographic method in detail, which is based on image segmentation using a complexity measure. They also introduce a method for applying this to palette-based image formats, reversible information hiding for grayscale images, and JPEG2000 steganography. The steganographic methods for JPEG and JPEG2000 described in this chapter give particular consideration to the naturalness of cover data. In the steganalysis section, the authors introduce two methods, i.e., a specific steganalysis method for LSB steganography and Bit-Plane Complexity Segmentation (BPCS) stegnography.