Digital Watermarking for Multimedia Content Protection
The goal of this project is to devise novel methods for multimedia content protection through Digital Watermarking techniques which exploit several transforms, such as: Discrete Wavelet, Singular Value Decomposition and Karhunen-Loeve.
A common solution to counter the unauthorized distribution of copyrighted contents is applied by means of digital watermarking. This term refers to specific information hiding techniques whose purpose is to embed secret information inside multimedia contents, such as images, video or audio streams.
Two different projects have been carried out: the first exploits properties of the SVD transform to watermark grayscale images, whereas the second focuses on the watermarking of color images through the Karhunen-Loeve transform.
Knowing that the features of the Singular Value Decomposition transform are extremely robust against common and geometric attack, we devised a block-wise watermarking scheme in this domain. The proposed scheme works by initially splitting the original image into non-overlapping blocks, applying the SVD transform to each of them and subsequently embedding a watermark into the singular vectors. Each watermark value is embedded by modifying a set of singular vector angles, i.e., angles formed by the right singular vectors of each block The main contribution of this work can be identified in:
The Karhunen-Lo?ve transform (KLT), also known as Principal Component Analysis (PCA), is a linear transformation that maps a set of vectors between two spaces. A fundamental property of the KLT is that it is the best transform with regard to the ability of compacting, on average, the maximum possible energy when a limited number of vector components are used. This property has made it useful in many compression algorithms and signal processing applications.
We devised a novel watermarking scheme for color images, based on the Karhunen-Lo?ve transform (KLT) that exploit the above mentioned properties and uses a normally distributed, zero mean, pseudo-random sequence as watermark. The novelty of the method resides in the fact that the KLT basis images used for the transforms are not related to the image being marked, but are from an image being part of the secret key used in the watermarking scheme. Experimental results show a good robustness against a wide range of signal processing operations and attacks. Moreover, the quality of the original image is preserved during the watermarking process.