While Digital Watermarking has received much attention in recent
years, it is still a relatively young technology. There are few
accepted tools/metrics that can be used to evaluate the suitability
of a watermarking technique for a specific application. This lack of
a universally adopted set of metrics/methods has motivated us to
develop a web-based digital watermark evaluation system called the
Watermark Evaluation Testbed or WET. There have been
more improvements over the first version of WET. We
implemented batch mode with a queue that allows for user submitted
jobs. In addition to StirMark 3.1 as an attack module, we added
attack modules based on StirMark 4.0. For a new image fidelity
measure, we evaluate conditional entropy as an image fidelity
measure for different watermarking algorithms and different attacks.
Also, we show the results of curve fitting the Receiver Operating
Characteristic (ROC) analysis data using the Parzen window density
estimation. The curve fits the data closely while having only two
parameters to estimate.
Methodologies and tools for watermark evaluation and benchmarking facilitate the development of improved watermarking techniques. In this paper, we want to introduce and discuss the integration of audio watermark evaluation methods into the well-known web service Watermark Evaluation Testbed (WET). WET is enhanced by using. A special set of audio files with characterized content and a collection of single attacks as well as attack profiles will help to select special audio files and attacks with their attack parameters.
In this paper, we propose a new region-based method for detecting mass tumors in digital mammograms. Our method uses principal component analysis (PCA) techniques to reduce the image data into a subspace with significantly reduced dimensionality using an optimal linear transformation. After the transformation, classification in the subspace is performed using a nearest neighbor classifier. We consider the detection of only mass abnormalities in this study. Micro calcifications, spiculated lesions, and other abnormalities are not considered. We implemented our method and achieved a 93% correct detection rate for mass abnormalities in our tests.
We describe a blind watermarking technique for digital images. Our technique constructs an image-dependent watermark in the discrete wavelet transform (DWT) domain and inserts the watermark in the most signifcant coefficients of the image. The watermarked coefficients are determined by using the hierarchical tree structure induced by the DWT, similar in concept to embedded zerotree wavelet (EZW) compression. If the watermarked image is attacked or manipulated such that the set of significant coefficients is changed, the tree structure allows the correlation-based watermark detector to recover synchronization.
Our technique also uses a visual adaptive scheme to insert the watermark to minimize watermark perceptibility. The visual adaptive scheme also takes advantage of the tree structure. Finally, a template is inserted into the watermark to provide robustness against geometric attacks. The template detection uses the cross-ratio of four collinear points.
Recently, we proposed a method for constructing a template for efficient temporal synchronization in video watermarking. Our temporal synchronization method uses a state machine key generator for producing the watermark embedded in successive frames of video. A feature extractor allows the watermark key schedule to be content dependent, increasing the difficulty of copy and ownership attacks. It was shown that efficient synchronization can be achieved by adding temporal redundancy into the key schedule.
In this paper, we explore and extend the concepts of our temporal synchronization method to spatial synchronization. The key generator is used to construct the embedded watermark of non-overlapping blocks of the video, creating a tiled structure. The autocorrelation of the tiled watermark contains local maxima or peaks with a grid-like structure, where the distance between the peaks indicates the scale of the watermark and the orientation of the peaks indicate the watermark rotation. Experimental results are obtained using digital image watermarks. Scaling and rotation attacks are investigated.
In refernce one, we proposed a technique or protocol for efficient temporal synchronization of video watermarks. Our technique is based on constructing a watermark with temporal redundancy, which allows the detector to efficiently establish and maintain synchronization without performing extensive search or explicit template signal embedding. In this paper, we describe several enhancements to our technique. A new class of key generators is presented which uses a cryptographic hash function to define the set of states and the state transition function of the finite state machine (FSM). In addition to the very large number of states and key-dependent state transition functions, which enhance security, the new class of key generators allows a limited degree of randomization. This randomization can take the form of multiple start states in the FSM, or by randomized state transitions. The non-deterministic behavior of a randomized FSM requires the detector to perform more search, but also makes the key sequence less predictable and improves security. We also describe a new method for temporal redundancy control which adaptively changes the watermark key based on the characteristics of the video. This new strategy prevents a loss of temporal redundancy (which leads to a loss of robustness) which can occur using the earlier naive method. The enhancements were implemented and the detection performance after frame dropping, transposition, and averaging attack are compared.
A novel watermarking algorithm for watermarking low bit-rate MPEG-4 compressed video is developed and evaluated in this paper. Spatial spread spectrum is used to invisibly embed the watermark into the host video. A master synchronization template is also used to combat geometrical distortion such as cropping, scaling, and rotation. The same master synchronization template is used for watermarking all video objects (VOP) in the bit-stream, but each object can be watermarked with a unique payload. A gain control algorithm is used to adjust the local gain of the watermark, in order to maximize watermark robustness and minimize the impact on the quality of the video. A spatial and temporal drift compensator is used to eliminate watermark self-interference and the drift in quality due to AC/DC prediction in I-VOPs and motion compensation in P- and B-VOPs, respectively. Finally, a bit-rate controller is used to maintain the data-rate at an acceptable level after embedding the watermark. The developed watermarking algorithm is tested using several bit-streams at bit-rates ranging from 128-750 Kbit/s. The visibility and the robustness of the watermark after decompression, rotation, scaling, sharpening, noise reduction, and trans-coding are evaluated.
This paper examines the problems with temporal synchronization in video watermarking and describes a new method for efficient synchronization and resynchronization. In our method, efficient synchronization is achieved by designing temporal redundancy in the structure of the watermark. Temporal redundancy allows the watermark detector to establish and maintain synchronization without performing extensive search in the watermark key space. Our method does not use synchronization templates that may be subject to attack and increase the visibility of the watermark. Another advantage of our technique is that the watermark structure is video-dependent, which enhances security. The technique is implemented using a spatial domain watermark on uncompressed video and a finite state machine watermark key generator. The implementation illustrates the effectiveness of using temporal redundancy for synchronization, and is shown to be resilient to desynchronization attacks such as frame dropping, frame insertion, local frame transposition, and frame averaging. Our method for synchronization is independent of the embedding method and can be used with a wide class of watermark embedding and detection techniques, including those for other time-varying signals such as digital audio.
Video streaming, or the real-time delivery of video over a data network, is the underlying technology behind many applications including video conferencing, video-on-demand, and the delivery of educational and entertainment content. In many applications, particularly ones involving entertainment content, security issues, such as conditional access and copy protection must be addressed. To resolve these security issues, techniques that include encryption and watermarking need to be developed. Since the video sequences will often be compressed using a scalable compression technique and transported over a lossy packet network using the Internet Protocol, the security techniques must be compatible with the compression method and data transport and be robust to errors. In this paper, we address the issues involved in the watermarking of rate-scalable video streams delivered using a practical network. Watermarking is the embedding of a signal (the watermark) into a video stream that is imperceptible when the stream is viewed but can be detected by a watermark detector. Many watermarking techniques have been proposed for digital images and video, but the issues of streaming have not been fully investigated. A review of streaming video is presented, including scalable video compression and network transport, followed by a brief review of video watermarking and the discussion of watermarking streaming video.
Digital watermarking research has generally focused upon two classes of watermarks, fragile and robust. Robust watermarks are designed to be detected even after attempts are made to remove them. Fragile watermarks are used for authentication purposes and are capable of detecting even minute changes of the watermarked content. Unfortunately, neither type of watermark is ideal when considering 'information preserving' transformations (such as compression) which preserve the meaning or expression of the content and 'information altering' transformations (such as feature replacement) which change the expression of the content. In this paper we describe a semi-fragile watermark for still images that can detect information altering transformations even after the watermarked content is subjected to information preserving alterations.