Aweke Negash Lemma

A temporal domain audio watermarking technique

Audio watermarking techniques can be used to embed extra information into audio signals. The goal is to hide prespecified data carrying some information into the audio stream such that it is not audible to the human ear (i.e., transparent) and is, at the same time, resistant to removal attacks (i.e., robust). In the currently known watermarking systems, the above challenges are not always adequately resolved. We present an alternative audio watermarking technique that mitigates these and other related shortcomings. The system is referred to as modified audio signal keying (MASK). In MASK, the short-time envelope of the audio signal is modified in such a way that the change is imperceptible to the human listener. The MASK system can easily be tailored for a wide range of applications. Moreover, informal experimental results show that it has a good robustness and audibility behavior.

Secure watermark embedding through partial encryption

Secure watermark embedding allows to securely embed a watermark into a piece of content at an untrusted user device without compromising the security of the watermark key, the watermark or the original. In this paper, we show how secure embedding can be achieved by using traditional watermarking schemes in conjunction with partial encryption techniques, which were primarily developed to facilitate fast encryption of media content. Based on this concept, we develop two new efficient secure embedding mechanisms, one for the MASK watermarking scheme operating on baseband audio and one for a spread spectrum watermarking scheme operating on MPEG-2 encoded video streams.

A Buyer–Seller Watermarking Protocol Based on Secure Embedding

In a forensic watermarking architecture, a buyer-seller protocol protects the watermark secrets from the buyer and prevents false infringement accusations by the seller. Existing protocols encrypt the watermark and the content with a homomorphic public-key cipher and perform embedding under encryption. When used for multimedia data, these protocols create a large computation and bandwidth overhead. In this correspondence, we show that the same functionality can be achieved efficiently using recently proposed secure watermark embedding algorithms.

Lookup-Table-Based Secure Client-Side Embedding for Spread-Spectrum Watermarks

Today, mass-scale electronic content distribution systems embed forensic tracking watermarks primarily at the distribution server. For limiting the bandwidth usage and server complexity and enhancing scalability, it is preferable to embed the watermark at the client. Embedding in these untrusted clients requires secure embedding methods that do not leak unmarked content or the watermarking secrets. In this work, we propose a secure watermark embedding scheme based on lookup tables for spread-spectrum watermarks, which are robust to noise and can be detected without comparison to the original content. We also develop fast detection mechanisms that make the watermark detection feasible for tracking systems with a large number of clients. Our fast detection algorithm improves detection speed of existing methods by six orders of magnitude in a typical system with millions of clients.

A secure multidimensional point inclusion protocol

Signal processing in the encrypted domain combines typical signal processing operations and cryptographic primitives to ensure security in applications involving mutually distrusting participants. Several such applications reduce to a multidimensional point inclusion problem where two participants decide whether a point known to the first lies inside a region specified by the second. In a secure solution, neither party gains knowledge about the others input. For instance, in biometric authentication the client can prove his identity without disclosing his biometric. In this paper, we present a new primitive for securely solving the multidimensional point inclusion problem. Using this primitive, we first propose an efficient and provably secure protocol that solves the problem for an N-dimensional convex region bounded with hyperplanes. We subsequently extend the protocol to inclusion in multiple hyperellipsoidal regions. Considering possible reduction strategies such as input packing, we analyze the complexity of both protocols.

Secure Embedding of Spread Spectrum Watermarks using Look-up-Tables

In an electronic content distribution system, it is preferable to embed forensic tracking watermarks at the client-side to limit bandwidth usage and server complexity. Embedding in these untrusted clients, however, requires secure embedding methods that do not leak unmarked contents or the watermarking secrets. In this work, we propose a look-up-table (LUT) based cipher, similar to Andersens Chameleon cipher, for securely embedding spread-spectrum watermarks, which are noise robust and detectable without the original content. We also develop fast detection mechanisms that make the watermark detection feasible for tracking systems with large number of clients. Our fast detection algorithm improves detection speed six orders of magnitude in a typical system.

Informed detection of audio watermark for resolving playback speed modifications

In this paper, we present a method for informed watermark detection in audio signals. In this context, informed detection refers to the mechanism in which the original media signal is used to improve robustness and/or complexity. Here, we focused on reducing complexity by addressing the geometrical distortion problem. In audio, geometrical distortion translates to time scaling. Generally, s speed changes of the audio signals necessitate a mechanism in the detector to retrieve the watermark. Usually this is done by some kind of (clever) exhaustive search algorithms. In this paper we show that the speed searching process can significantly be improved using fingerprinting technology. Particularly, an initial estimate of the speed is obtained by extracting the so-called local fingerprint time stamps. This initial estimate is then used as a starting point for the exhaustive speed search algorithm in the watermark detector. We also give analyses on the accuracies of the watermark detector and the fingerprint algorithm and the relations thereof. Moreover, we present the concept for integrating fingerprint algorithm in the watermark detector and discuss the influence of various parameters. We show that, apart from a significant complexity reduction, such integration can lead to an improvement in robustness as a byproduct.

Electronic content delivery and forensic watermarking

Today, digital content distribution is already common practice for media types like audio. It is expected that in the near future, systems like Video-on-Demand will also increase in popularity. Many Digital Right Management (DRM) models exist enforcing the copyrights associated with the distributed content. We argue that a simplified model based on so-called forensic watermarks is a viable alternative approach that closely mimics the current model of physical music and video distribution by providing a reasonable compromise between the conflicting interests of consumers and content owners. In this paper, we address the forensic watermark DRM model and introduce a generalized architecture for the distribution server and the forensic watermark tracker. In this model, important attack scenarios are identified as being the ‘copy attack’ and the watermark ‘rendering’. We show that it is more difficult to successfully work out these attack scenarios by (i) integrating a content identification and watermarking system and (ii) making the watermark (both the carrier signal as well as the payload) content dependent. In addition to these security aspects, we also focus on efficiency of the distribution server. By separating the computational efforts in so-called pre-coding and on-line computational phases, the required signal processing resources of the distribution server can be reduced significantly. The general architecture including security and efficiency requirements are analyzed in a practical example of Electronic Music Delivery (EMD). We show that computational complexity can be reduced up to a factor 4 compared to a straightforward approach. In practice, it means that with current state-of-the art computers (Pentium IV, 1 GHz) watermark embedding speeds of about 40 times Real Time (RT) can be achieved. In addition to the embedding architecture, we also demonstrate an efficient method for detecting watermarks in a forensic watermark tracker. Having multimedia identification fingerprints available (required for working with content-dependent watermarks), the efficiency of watermark detection can be enhanced by using them as side information. Again, in our EMD prototype, we demonstrate that (depending on the parameter settings) the detector can run up to 50 times faster than a blind detector, in which the original or the fingerprint is not available.

Camcorder Capture Robust Low-Complexity Watermarking of MPEG-2 Bit-Streams

Unauthorized re-distribution remains a significant threat for emerging electronic movie distribution services. In this paper, we propose a forensic tracking watermark for MPEG-2 bit-streams that can be employed to complement Digital Rights Management and conditional access systems in electronic movie distribution. The watermark is embedded by modulating a subset of quantization matrix entries, which are periodically present in the MPEG-2 headers. When observed over time the watermark can be detected even after cropping, de-interlacing, resizing and DivX compression at 300 kbps or after being captured with a video camera from a flat-screen TV. As the method modifies only a small part of the bit-stream (ap100 bytes per second), it can be readily implemented in resource constrained environments like the current generation set-top boxes, without costly hardware upgrades.

Decode-Time Forensic Watermarking of AAC Bitstreams

In digital rights-management systems, forensic watermarking complements encryption and deters the capture and unauthorized redistribution of the rendered content. In this paper, we propose a novel watermarking method which is integrated into the advanced audio coding (AAC) standards decoding process. For predefined frequency bands, the method intercepts and modifies the scale factors, which are utilized for dequantization of spectral coefficients. It thereby modulates the short-time envelope of the bandlimited audio and embeds a watermark which is robust to various attacks, such as capture with a microphone and recompression at lower bit rates. Inclusion of watermark embedding in the AAC decoder has practically no effect on the decoding complexity. As a result, the proposed method can be integrated even into resource-constrained devices, such as portable players without any additional hardware.