Digital watermarking is a key ingredient to copyright protection. It provides a solution to illegal copying of digital material and has many other useful applications such as broadcast monitoring and the recording of electronic transactions. Now, for the first time, there is a book that focuses exclusively on this exciting technology. Digital Watermarking covers the crucial research findings in the field: it explains the principles underlying digital watermarking technologies, describes the requirements that have given rise to them, and discusses the diverse ends to which these technologies are being applied. As a result, additional groundwork is laid for future developments in this field, helping the reader understand and anticipate new approaches and applications.

Digital Watermarking

Trends in extreme learning machines

Currently, the most successful approach to steganography in empirical objects, such as digital media, is to embed the payload while minimizing a suitably defined distortion function. The design of the distortion is essentially the only task left to the steganographer since efficient practical codes exist that embed near the payload-distortion bound. The practitioner’s goal is to design the distortion to obtain a scheme with a high empirical statistical detectability. In this paper, we propose a universal distortion design called universal wavelet relative distortion (UNIWARD) that can be applied for embedding in an arbitrary domain. The embedding distortion is computed as a sum of relative changes of coefficients in a directional filter bank decomposition of the cover image. The directionality forces the embedding changes to such parts of the cover object that are difficult to model in multiple directions, such as textures or noisy regions, while avoiding smooth regions or clean edges. We demonstrate experimentally using rich models as well as targeted attacks that steganographic methods built using UNIWARD match or outperform the current state of the art in the spatial domain, JPEG domain, and side-informed JPEG domain.

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Universal distortion function for steganography in an arbitrary domain

This paper presents a complete methodology for designing practical and highly-undetectable stegosystems for real digital media. The main design principle is to minimize a suitably-defined distortion by means of efficient coding algorithm. The distortion is defined as a weighted difference of extended state-of-the-art feature vectors already used in steganalysis. This allows us to "preserve" the model used by steganalyst and thus be undetectable even for large payloads. This framework can be efficiently implemented even when the dimensionality of the feature set used by the embedder is larger than 107. The high dimensional model is necessary to avoid known security weaknesses. Although high-dimensional models might be problem in steganalysis, we explain, why they are acceptable in steganography. As an example, we introduce HUGO, a new embedding algorithm for spatial-domain digital images and we contrast its performance with LSB matching. On the BOWS2 image database and in contrast with LSB matching, HUGO allows the embedder to hide 7× longer message with the same level of security level.

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Using high-dimensional image models to perform highly undetectable steganography

This paper presents a reversible or lossless watermarking algorithm for images without using a location map in most cases. This algorithm employs prediction errors to embed data into an image. A sorting technique is used to record the prediction errors based on magnitude of its local variance. Using sorted prediction errors and, if needed, though rarely, a reduced size location map allows us to embed more data into the image with less distortion. The performance of the proposed reversible watermarking scheme is evaluated using different images and compared with four methods: those of Kamstra and Heijmans, Thodi and Rodriguez, and Lee et al. The results clearly indicate that the proposed scheme can embed more data with less distortion.

Reversible Watermarking Algorithm Using Sorting and Prediction

A nested dissection ordering algorithm is adopted into the ICCG (incomplete Cholesky factorization for conjugate gradient) iterative solver, which can improve the convergence rate of the ICCG method in some cases. The ordering effects on the FE meshes are investigated with the convergence rate variation. It turns out that the ordering in the FE meshes has little effect against the acceleration factor in practical use. The method is applied to induction motors.

On the convergence rate improvement of ICCG solver on the FE mesh

A new data hiding method completely secure against the first-order statistical attack is proposed. This method separates the selective and non-selective blocks first, selects the selective blocks next, and shifts the position of last non-zero AC coefficients to embed secret messages. Even after hiding data, non-zero JPEG coefficients remain unchanged. Since this method does not change the AC coefficients, but changes their positions, the produced histogram of the image after data hiding remains the same as that of original image.

Secure steganographic method

This paper presents a novel reversible data hiding method which uses a combined predictor. The proposed combined predictor combines five base predictors according to their global and local predicting performance. The weights to combine the base predictors are calculated with a pixel by pixel manner that they adjust to the local image patch characteristics. The proposed predictor is shown to have high prediction precision which is beneficial for the following prediction error expansion (PEE). Observing that our predictor performs well even for images with complex textures, a novel pixel selection criterion that bases on the prediction errors is proposed, which can accurately select the pixels that have small prediction errors to use. Extensive experiments are conducted to verify the superior performance of the proposed method.

Reversible Data Hiding Based on Combined Predictor and Prediction Error Expansion

A proxy re-encryption scheme allows Alice to temporarily delegate the decryption rights to Bob via a proxy. Alice gives the proxy a re-encryption key so that the proxy can convert a ciphertext for Alice into the ciphertext for Bob. Recently, ID-based proxy re-encryption schemes are receiving considerable attention for a variety of applications such as distributed storage, DRM, and email-forwarding system. And a non-interactive identity-based proxy re-encryption scheme was proposed for achieving CCA-security by Green and Ateniese. In the paper, we show that the identity-based proxy re-encryption scheme is unfortunately vulnerable to a collusion attack. The collusion of a proxy and a malicious user enables two parties to derive other honest users' private keys and thereby decrypt ciphertexts intended for only the honest user. To solve this problem, we propose two ID-based proxy re-encryption scheme schemes, which are proved secure under CPA and CCA in the random oracle model. For achieving CCA-security, we present self-authentication tag based on short signature. Important features of proposed scheme is that ciphertext structure is preserved after the ciphertext is re-encrypted. Therefore it does not lead to ciphertext expansion. And there is no limitation on the number of re-encryption.

ID-Based Proxy Re-encryption Scheme with Chosen-Ciphertext Security

In transformed and compressed domain fragmented files are very difficult to recover using conventional file recovery software. JPEG images are forensically important file format due to its popularity in a wide area of applications. In JPEG compression the header keeps important parameters that are required to decode the image back to pixel domain. In this paper the detection of width and height of an image from the JPEG stream is improved with less assumptions than previous papers. In the old approaches it was assumed that information about the image like Huffman table, Reset (RST) value and Quantization table were readily available for the techniques to work. However, in this paper the width is extracted from the quantized AC values that reduce the assumptions to just Huffman table.

Hyoung Joong Kim

Papers

On the convergence rate improvement of ICCG solver on the FE mesh

Secure steganographic method

Reversible Data Hiding Based on Combined Predictor and Prediction Error Expansion

ID-Based Proxy Re-encryption Scheme with Chosen-Ciphertext Security

Early width estimation of fragmented JPEG with corrupted header