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## Über dieses Buch

Since the mid 1990s, data hiding has been proposed as an enabling technology for securing multimedia communication and is now used in various applications including broadcast monitoring, movie fingerprinting, steganography, video indexing and retrieval and image authentication. Data hiding and cryptographic techniques are often combined to complement each other, thus triggering the development of a new research field of multimedia security. Besides, two related disciplines, steganalysis and data forensics, are increasingly attracting researchers and becoming another new research field of multimedia security. This journal, LNCS Transactions on Data Hiding and Multimedia Security, aims to be a forum for all researchers in these emerging fields, publishing both original and archival research results. The six papers included in this issue deal with watermarking security, perceptual image hashing, infrared hiding, steganography and steganalysis.

## Inhaltsverzeichnis

### Strengthening Spread Spectrum Watermarking Security via Key Controlled Wavelet Filter

Abstract
Spread spectrum watermarking security can be evaluated via mutual information. In this paper, we present a new method to reduce mutual information by embedding watermark in the key controlled wavelet domain. Theoretical analysis shows that the watermark signals are diffused and its energy is weakened when they are evaluated from the attacker’s observation domain, and it can lead to higher document-to-watermark energy ratio and better watermark security without losing robustness. Practical algorithms of security tests using optimal estimators are also applied and the performance of the estimators in the observation domain is studied. Besides, we also present a novel method of calculating the key controlled wavelet filter, and give both numerical and analytical implementations. Experiment results show that this method provides more valid parameters than existing methods.
Bingbing Xia, Xianfeng Zhao, Dengguo Feng, Mingsheng Wang

### Wave Atom-Based Perceptual Image Hashing Against Content-Preserving and Content-Altering Attacks

Abstract
This paper presents a perceptual image hashing algorithm based on wave atom transform, which can distinguish maliciously attacked images from content-preserving ones. Wave atoms are employed due to their significantly sparser expansion and better feature extraction capability than traditional transforms, like discrete cosine transform (DCT) and discrete wavelet transform (DWT). Thus, it is expected to show better performance in image hashing. Moreover, a preprocessing method based on Fourier-Mellin transform is employed to keep the proposed scheme against geometric attacks. In addition, a randomized pixel modulation based on RC4 is performed to ensure the security. According to the experimental results, the proposed scheme is sensitive to content-altering attacks with the resiliency of content-preserving operations, including image compression, noising, filtering, and rotation. Moreover, compared with some other image hashing algorithms, the proposed approach also achieves better performance even in the aspect of robustness, which is more important in some image hashing application, for example image database retrieval or digital watermarking.
Fang Liu, Lee-Ming Cheng

### IR Hiding: Use of Specular Reflection for Short-Wavelength-Pass-Filter Detection to Prevent Re-recording of Screen Images

Abstract
We previously proposed using infrared (IR) LEDs to corrupt recorded content to prevent the re-recording of images displayed on a screen. This method is based on the difference in sensory perception between humans and devices and prevents re-recording by adding IR noise to the images displayed on the screen without it being detected by the human eye. However, it cannot prevent re-recording using digital camcorders equipped with a short wavelength pass filter to eliminate the noise. We have now improved our method by adding a simple countermeasure against such attacks. It detects IR light reflected off the filter by using the IR specular reflection properties of the filter and thereby detects re-recording using digital camcorders equipped with a short wavelength pass filter. We implemented this countermeasure by adding one of two types of IR LEDs (bullet type and chip type with lens) to our prototype re-recording prevention system, which is installed on a B3-size screen. Testing showed that this enhanced system can detect camcorders with an attached short wavelength pass filter.
Isao Echizen, Takayuki Yamada, Seiichi Gohshi

### A Reliable Covert Communication Scheme Based on VoIP Steganography

Abstract
Steganography is the science of hiding information in such a way that an adversary wouldn’t know it existed. A significant amount of research has been done in this field for non-real time mediums. Research on real time mediums, for example Voice over Internet Protocol (VoIP), isn’t as mature. In this paper, we propose an algorithm that enables data hiding in G.711, the most commonly used voice codec for VoIP devices, while gracefully handling packet loss. This would allow two telephone users to covertly transfer multiple pieces of arbitrary information between their respective systems in a reliable manner. We use important performance metrics to evaluate our algorithm, namely, throughput, noise-to-signal ratio and the Perceptual Evaluation of Speech Quality algorithm. We demonstrate that our algorithm performs well compared to other algorithms proposed in the literature in real world environments, where packet loss is inevitable, by maintaining high throughput and good speech quality.
Harrison Neal, Hala ElAarag

### Adaptive Steganography and Steganalysis with Fixed-Size Embedding

Abstract
We analyze a two-player zero-sum game between a steganographer, Alice, and a steganalyst, Eve. In this game, Alice wants to hide a secret message of length $$k$$ in a binary sequence, and Eve wants to detect whether a secret message is present. The individual positions of all binary sequences are independently distributed, but have different levels of predictability. Using knowledge of this distribution, Alice randomizes over all possible size-$$k$$ subsets of embedding positions. Eve uses an optimal (possibly randomized) decision rule that considers all positions, and incorporates knowledge of both the sequence distribution and Alice’s embedding strategy.
Our model extends prior work by removing restrictions on Eve’s detection power. We give defining formulas for each player’s best response strategy and minimax strategy; and we present additional structural constraints on the game’s equilibria. For the special case of length-two binary sequences, we compute explicit equilibria and provide numerical illustrations.
Benjamin Johnson, Pascal Schöttle, Aron Laszka, Jens Grossklags, Rainer Böhme

### Permutation Steganography in FAT Filesystems

Abstract
It is easy to focus on elaborate steganographic schemes and forget that even straightforward ones can have a devastating impact in an enterprise setting, if they allow information to be exfiltrated from the organization.
To this end, we offer a cautionary tale: we show how messages may be hidden in FAT filesystems using the permutation of filenames, a method that allows a hidden message to be embedded using regular file copy commands. A straightforward scheme, but effective. Our experiments on seven different platforms show that the existence of the hidden message is obscured in practice in the vast majority of cases.
John Aycock, Daniel Medeiros Nunes de Castro

### Backmatter

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