Joint Image Encryption and Screen-Cam Robust Two Watermarking Scheme

This paper proposes a joint encryption and screen-cam robust watermarking scheme. This method combines the advantages of smartphone, encryption and watermarking technologies, thereby achieving watermark extraction with a smartphone, partial decryption and tracking leakage from sneak shots. We design a dual watermarking algorithm to achieve watermark detection from both encrypted and decrypted images. First, a watermark is embedded in the discrete Fourier transform (DFT) domain to enable leakage tracking. Then, a second watermark is generated based on QR (Quick response) code encoding and inverse DFT to achieve high watermark capacity and error correction ability, where the secret key for decryption is included in the watermark message. By hiding this message carrying the watermark for the encrypted image in the changes caused by embedding the first watermark, we can improve imperceptibility and will not affect the effectiveness of the proposed scheme. Finally, to enhance the robustness of watermark after encryption, a chaotic mapping-based segment encryption algorithm is proposed. In the process of watermark detection, to cope with perspective correction, a frame locating based algorithm is employed to achieve watermark synchronization from a recaptured picture of the encrypted image. Considering the severe quality degradation, we use a noise component and local statistic feature-based method to extract the message bits. The experimental results show that the proposed scheme is secure, and highly robust, to screen-cam the process for both before and after decryption. Additionally, after decryption, the proposed scheme also has high robustness against common image processing attacks.

Screen-Cam Robust Image Watermarking with Feature-Based Synchronization

The screen-cam process, which is taking pictures of the content displayed on a screen with mobile phones or cameras, is one of the main ways that image information is leaked. However, traditional image watermarking methods are not resilient to screen-cam processes with severe distortion. In this paper, a screen-cam robust watermarking scheme with a feature-based synchronization method is proposed. First, the distortions caused by the screen-cam process are investigated. These distortions can be summarized into the five categories of linear distortion, gamma tweaking, geometric distortion, noise attack, and low-pass filtering attack. Then, a local square feature region (LSFR) construction method based on a Gaussian function, modified Harris–Laplace detector, and speeded-up robust feature (SURF) orientation descriptor is developed for watermark synchronization. Next, the message is repeatedly embedded in each selected LSFR by an improved embedding algorithm, which employs a non-rotating embedding method and a preprocessing method, to modulate the discrete Fourier transform (DFT) coefficients. In the process of watermark detection, we fully utilize the captured information and extract the message based on a local statistical feature. Finally, the experimental results are presented to illustrate the effectiveness of the method against common attacks and screen-cam attacks. Compared to the previous schemes, our scheme has not only good robustness against screen-cam attack, but is also effective against screen-cam with additional common desynchronization attacks.

Estimating Digital Watermark Synchronization Signal Using Partial Pixel Least Squares

To read a digital watermark from printed images requires that the watermarking system read correctly after affine distortions. One way to recover from affine distortions is to add a synchronization signal in the Fourier frequency domain and use this synchronization signal to estimate the applied affine distortion. If the synchronization signal contains a collection of frequency impulses, then a least squares match of frequency impulse locations results in a reasonably accurate linear transform estimation. Nearest neighbor frequency impulse peak location estimation provides a good rough estimate for the linear transform, but a more accurate refinement of the least squares estimate is accomplished with partial pixel peak location estimates. In this paper we will show how to estimate peak locations to any desired accuracy using only the complex frequencies computed by the standard DFT. We will show that these improved peak location estimates result in a more accurate linear transform estimate. We conclude with an assessment of detector robustness that results from this improved linear transformation accuracy.

Randon and Ridgelet Transformation Applicaton in Image Digital Watermark

Propose a digital watermark algorithm that can be resisted geometric attack, in order to enhance the capacity to resist attacks such as rotation, use the 0° angle Randon transformation as the reference vector, estimate and correct the rotation transformation of the carrier image, recover the watermark synchronization. when watermark is embedded, perform wavelet transform on original image and blocked the LF sub-band, perform the Ridgelet transformation on each block; change two-value watermark to one-dimension, embedded the watermark bit into the Maximum energy direction of Ridgelet. The simulation results show that the algorithm can effective resist various attacks such as noise, filtering, compression, rotation, shearing and scaling etc, and the ability of resist various attacks is robust.

A Novel Watermarking Algorithm Based on SURF and SVD

A novel watermarking algorithm based on SURF (Speeded Up Robust Features) and Singular Value Decomposition (SVD) is presented for copyright protection. By introducing the SURF’s key points matching and geometric distortion estimation, the attacked watermarked image can be corrected and the watermark synchronization is realized. In this way, the feature regions of the host image, which are used for information hiding, can be correctly detected by the improved Harris-Laplace corner detector even after signal processing and geometric attacks. The application of the proposed scheme makes the watermark capable of transparent hiding. Extensive experimental results demonstrate that our technique performs better than traditional methods under different attacks.

A Survey of Current Watermarking Synchronization Techniques

The resistance of watermarking schemes against geometric distortions has been the subject of much research and development effort in the last 10 years. This is due to the fact that even the minor geometric, manipulation of the watermarked image can dramatically reduce the ability of the watermark detector to detect the watermark, that is, the watermark detector can lose the synchronization. By this, the watermark synchronization can be defined as a process for finding the location for watermark embedding and detection. A variety of techniques have been proposed to provide partial robustness against geometrical distortions. These techniques can be divided into two groups: (1) techniques that use the original image to recover to synchronization and (2) techniques that do not have the access to the original image content during the synchronization process. This chapter classifies and analyzes techniques and approaches that are currently used in watermarking schemes to recover the synchronization.