Joséph John O'Ruanaidh

Rotation, scale and translation invariant spread spectrum digital image watermarking

Abstract A digital watermark is an invisible mark embedded in a digital image which may be used for a number of different purposes including image captioning and copyright protection. This paper describes how a combination of spread spectrum encoding of the embedded message and transform-based invariants can be used for digital image watermarking. In particular, it is described how a Fourier–Mellin-based approach can be used to construct watermarks which are designed to be unaffected by any combination of rotation and scale transformations. In addition, a novel method of CDMA spread spectrum encoding is introduced which allows one to embed watermark messages of arbitrary length and which need only a secret key for decoding. The paper also describes the usefulness of Reed Solomon error-correcting codes in this scheme.

Rotation, scale and translation invariant digital image watermarking

A digital watermark is an invisible mark embedded in a digital image which may be used for copyright protection. This paper proposes that Fourier-Mellin transform-based invariants can be used for digital image watermarking. The embedded marks may be designed to be unaffected by any combination of rotation, scale and translation transformations. The original image is not required for extracting the embedded mark.

Robust 3D DFT video watermarking

This paper proposes a new approach for digital watermarking and secure copyright protection of videos, the principal aim being to discourage illicit copying and distribution of copyrighted material. The method presented here is based on the discrete Fourier transform (DFT) of three dimensional chunks of video scene, in contrast with previous works on video watermarking where each video frame was marked separately, or where only intra-frame or motion compensation parameters were marked in MPEG compressed videos. Two kinds of information are hidden in the video: a watermark and a template. Both are encoded using an owner key to ensure the system security and are embedded in the 3D DFT magnitude of video chunks. The watermark is a copyright information encoded in the form of a spread spectrum signal. The template is a key based grid and is used to detect and invert the effect of frame-rate changes, aspect-ratio modification and rescaling of frames. The template search and matching is performed in the log-log-log map of the 3D DFT magnitude. The performance of the presented technique is evaluated experimentally and compared with a frame-by-frame 2D DFT watermarking approach.

Secure robust digital watermarking using the lapped orthogonal transform

Digital watermarks have been proposed as a method for discouraging illicit copying and distribution of copyright material. One approach to Transform Domain image watermarking is to divide the image into separate blocks and compute the transform of each block. The watermark is inserted in the transform domain and the inverse transform is then computed. Such an approach is particularly effective against JPEG compression where 8 X 8 blocks are used in conjunction with the DCT. Using small blocks allows the watermark to be embedded adaptively as a function of the luminance and texture. However for small block sizes blocking artifacts are observed when the strength of the watermark is increased. In order to circumvent this problem, we propose a new approach based on Lapped Orthogonal Transforms (LOT) in which the watermark is inserted adaptively into the LOT domain. Robustness of the watermark to operations such as lossy compression is achieved by using a spread spectrum signal which is added in the LOT domain. The keys used to embed the spread spectrum signal are generated, certified, authenticated and securely distributed using a public key infrastructure containing an electronic copyright office and a certification authority. In addition to the above we propose using an invisible template to reverse the effects of rotation, rescaling and cropping on a watermarked image. This separate invisible template is based on the properties of the Fourier Transform. Finally, we objectively evaluate the performance of the proposed algorithm in order to demonstrate the robustness of the proposed technique with respect to a number of common image processing including JPEG compression, rotation, scaling and cropping.

A secure robust digital image watermark

Digital watermarks have been proposed as a method for discouraging illicit copying and distribution of copyright material. This paper presents a new approach for the secure and robust copyright protection of digital images. The digital watermarks described in this paper are designed to be, as far as possible, invariant against image transformations such as rotation, translation, scaling and cropping. We concentrate especially on the desirable properties of the Fourier Transform and propose a novel technique based on an invisible template which allows us to reverse many of the effects of image processing on the digital watermark. Robustness of the watermark to operations such as lossy compression is achieved by using a perceptually adaptive spread spectrum communications approach, in which a spread spectrum signal is embedded in selected components of the magnitude spectrum of the image. The keys used to embed the spread spectrum signal are generated, certified, authenticated and securely distributed using a public key infrastructure containing an electronic copyright office and a certification authority. The security architecture used for this purpose is also outlined.