A novel blind color images watermarking based on SVD

Since the color image watermark has more bit information, it is a challenging problem to design a robust and blind color watermarking scheme for copyright protection. In this paper, a blind watermarking scheme based on singular value decomposition (SVD) is proposed. By analyzing the orthogonal matrix U via SVD, it is found that there exists a strong similarity correlation between the second row first column element and the third row first column element. Hence, this paper utilizes this property for image watermarking. Firstly, the 4 × 4 non-overlapping pixels block of each component in color host image is processed by SVD. And then, the color watermark is embedded by slightly modifying the value of the second row first column element and the third row first column one of U matrix, and the modified relation can be utilized to extract watermark. Experimental results, compared with the related existing methods, show that the proposed color image scheme has stronger robustness against most common attacks such as image compression, filtering, cropping, noise adding, blurring, scaling and sharpening et al.     

Block based embedding of encrypted watermarks using singular value decomposition

Watermarking is a solution to the problem of copyright protection of multimedia documents over the Internet. This paper presents a block based watermarking scheme using the singular value decomposition (SVD) algorithm to embed encrypted watermarks into digital images. The paper compares between the traditional method of Liu and the proposed method for embedding encrypted watermarks. Also, a permutation based encryption algorithm and a diffusion based encryption algorithm are compared as the watermark encryption algorithms. Experimental results show that the proposed method is superior to the traditional method of Liu for embedding encrypted watermarks and extracting them efficiently under attacks. Results also show that it is preferred to use permutation based encryption algorithms than diffusion based encryption algorithms for watermark encryption due to their lower sensitivity to attacks.     

Performance analysis on a watermarking method based on double random phase encoding technique

When digital watermarking is used for piracy tracking, different watermarks are needed to be embedded into different distributions of a digital product. Based on double random phase encoding (DRPE) technique, cascaded-phases iterative algorithm and random-phase-shift algorithm, Chen et al. proposed a method to generate many different embedded watermarks from one reference watermark, while the embedded watermark can be recognized by testing the correlation between the recovered watermark and the original reference watermark. In this way, only the reference watermark instead of the embedded watermarks needs to be stored and managed. However, since the recovered watermark may be different from the embedded watermark, especially under any image processing, the correlation between the recovered watermark and the reference watermark may be different from the correlation between the embedded watermark and the reference watermark, which may result in wrong recognition. In this paper, the performance of Chen's method was analyzed with numerical simulations. The results indicated that, to correctly recognize the embedded watermark, the number of generated embedded watermarks with Chen's method is limited.     

Symmetric Tardos fingerprinting codes for arbitrary alphabet sizes

Fingerprinting provides a means of tracing unauthorized redistribution of digital data by individually marking each authorized copy with a personalized serial number. In order to prevent a group of users from collectively escaping identification, collusion-secure fingerprinting codes have been proposed. In this paper, we introduce a new construction of a collusion-secure fingerprinting code which is similar to a recent construction by Tardos but achieves shorter code lengths and allows for codes over arbitrary alphabets. We present results for ‘symmetric’ coalition strategies. For binary alphabets and a false accusation probability , a code length of symbols is provably sufficient, for large c ₀, to withstand collusion attacks of up to c ₀ colluders. This improves Tardos’ construction by a factor of 10. Furthermore, invoking the Central Limit Theorem in the case of sufficiently large c ₀, we show that even a code length of is adequate. Assuming the restricted digit model, the code length can be further reduced by moving from a binary alphabet to a q-ary alphabet. Numerical results show that a reduction of 35% is achievable for q = 3 and 80% for q = 10.      

Statistical detection of digital holographic watermarking system

In this paper, we examine the statistical properties of the holographic watermarking system [C.J. Cheng, L.C. Lin, W.T. Dai, Opt. Commun. 248 (2005) 105] and facilitate a systematic way to determine an optimal threshold of the correlation signal for detecting the authorized mark pattern. The holographic watermarking system constructs a digital holographic watermark using modified Mach-Zehnder interferometric architecture, and the correlation signal is obtained using an optical VanderLugt 4-f correlator to identify the authorized mark in the watermarked image. To obtain the best detection performance, we use statistical modeling of the entire holographic watermarking system. Accordingly, we derive correlation signal statistics and hypothesis testing to obtain an optimal threshold for the watermark detector that minimizes the detection error. The theoretical result of this paper allows us to easily determine an optimal threshold and evaluate the robustness of the watermark detector. The robustness of the proposed optimal detector is evaluated using detection error, and detection performance is demonstrated by simulation experiments.