Matthew J. Holliman

Counterfeiting attacks on oblivious block-wise independent invisible watermarking schemes

In this paper, we describe a class of attacks on certain block-based oblivious watermarking schemes. We show that oblivious watermarking techniques that embed information into a host image in a block-wise independent fashion are vulnerable to a counterfeiting attack. Specifically, given a watermarked image, one can forge the watermark it contains into another image without knowing the secret key used for watermark insertion and in some cases even without explicitly knowing the watermark. We demonstrate successful implementations of this attack on a few watermarking techniques that have been proposed in the literature. We also describe a possible solution to this problem of block-wise independence that makes our attack computationally intractable.

Physical simulation for animation and visual effects: parallelization and characterization for chip multiprocessors

We explore the emerging application area of physics-based simulation for computer animation and visual special effects. In particular, we examine its parallelization potential and characterize its behavior on a chip multiprocessor (CMP). Applications in this domain model and simulate natural phenomena, and often direct visual components of motion pictures. We study a set of three workloads that exemplify the span and complexity of physical simulation applications used in a production environment: fluid dynamics, facial animation, and cloth simulation. They are computationally demanding, requiring from a few seconds to several minutes to simulate a single frame; therefore, they can benefit greatly from the acceleration possible with large scale CMPs. Starting with serial versions of these applications, we parallelize code accounting for at least 96% of the serial execution time, targeting a large number of threads.We then study the most expensive modules using a simulated 64-core CMP. For the code representing key modules, we achieve parallel scaling of 45x, 50x, and 30x for fluid, face, and cloth simulations, respectively. The modules have a spectrum of parallel task granularity and locking behavior, and all but one are dominated by loop-level parallelism. Many modules operate on streams of data. In some cases, modules iterate over their data, leading to significant temporal locality. This streaming behavior leads to very high on-die and main memory bandwidth requirements. Finally, most modules have little inter-thread communication since they are data-parallel, but a few require heavy communication between data-parallel operations.

Video applications on hyper-threading technology

This paper characterizes selected workloads of multimedia applications on current superscalar architectures, and then it characterizes the same workloads on Intel hyper-threading technology. This technology enables multiple threads to run in parallel on a processor, by interleaving instructions from different threads in the pipeline. The workloads, including video encoding, decoding, and watermark detection, are optimized for the Intel Pentium 4 processor. Even if the workloads are very well optimized for the Pentium 4 processor, most of the modules in these well-optimized workloads cannot fully utilize all the execution units available in the microprocessor, due to the inherently sequential constitution of the algorithms. Some of the modules are memory-bounded, while some are computation-bounded. Therefore, hyper-threading technology is a promising architecture feature that allows more CPU resources to be used at a given moment. Our goal is to provide a better explanation of the performance improvements that are possible in multimedia applications using hyper-threading technology. We demonstrate different task partition/scheduling schemes and discuss their trade-offs so that the reader can understand how to develop efficient applications on processors with hyper-threading technology.

Robust frame-dependent video watermarking

In this paper, we describe some of the problems associated with watermarking key management, with particular attention to the case of video. We also describe a possible solution to the problem, which is that of image-dependent watermarking, and briefly discuss some of the possible advantages to be gained from adopting such an approach. The paper also presents a simple, efficient means of robustly extracting bits from a video sequence. The algorithm has applications to secure, oblivious video watermark detection.

Improving media services on P2P networks

The Media Accelerating Peer Services system extends P2P infrastructures to improve multimedia services across heterogeneous computing platforms. In this article, we present an architecture and resource management and adaptation framework that transcends existing infrastructures to accommodate and accelerate multimedia peer applications and services. We also propose key technology components that support seamless adaptation of resources to enhance quality of service and the building of better tools and applications that utilize the peer-computing networks underlying power.

Digital watermarks: Shedding light on the invisible

Digital media promise rewards-and risk, chiefly in the potential for unauthorized replication and distribution. In the content protection debate, digital watermarks offer one solution.

Watermarking for automatic quality monitoring

In this paper, we propose a new application for digital watermarking, which is that of automatic quality assessment. We compare several schemes in the literature that could be applied to the problem, and describe the benefits of distortion-dependent watermarking for the application.

Quality evaluation of watermarked video

Watermarks not specifically designed to be visible should be imperceptible to maintain image or video quality. Watermark characteristics that affect visibility include watermark magnitude, the visual masking model used to determine relative magnitude values, watermark frequency content, and the degree of temporal variation of the watermark between frames. Video characteristics that affect the visibility of a watermark include subject and camera motion, color, resolution, texture, and patterns. We have investigated the effects of these characteristics on watermark visibility for MPEG-1, MPEG-2, and both uncompressed and compressed high-definition video. The average watermark strength that can be added to a video is determined by increasing the average watermark magnitude through the sequence in order to observe the point at which the watermark becomes perceptible. The first artifact to become visible depends on video and watermark characteristics.

Watermark extimation through local pixel correlation

Many invisible watermarking schemes can be modeled as the addition of a watermark signal to an image, yielding a watermarked variant perceptually similar to the original image. In this paper, we describe a method by which an attacker, given only an image watermarked with such a technique, can attempt to construct an approximation to the watermark. The technique estimates an embedded signal by taking advantage of the inter-pixel correlation typically found in natural images, thereby allowing for a method of both watermark removal and watermark forgery. Furthermore, the approach is computationally inexpensive, making it suitable for attacks on proposed video watermarking schemes.

Real-time detection of video watermark on Intel architecture

This work discusses implementation issues of real-time video/image/signal processing applications on personal computers. We give a list of performance optimization guidelines and demonstrate some examples by optimizing our video watermark detection scheme. In many applications, watermarking technology must have (1) the ability to be implemented at low cost, (2) robustness against common image processing operations, and (3) resilience against purely malicious attacks. Many works, including ours, have demonstrated watermark robustness and invisibility. This work demonstrates that, after some performance optimizations, we can decode a 704 X 480 MPEG-2 video and detect the watermarks, both in software, and display the decoded video frames in real-time on an Intel PentiumR III 500 MHz system. Currently, there is only 10.5% overhead of the watermark detection over video decoding. The cost of our optimized implementation is 43% lower than that of the unoptimized version. The optimization techniques demonstrated in this work can be applied to other watermarking schemes and other video/image/signal processing applications.