Robust watermarking and its applications to communication problems
Loading...
Date
2012-05-14
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Abstract
Digital watermarking has recently gained an intense interest in research
and applications. An invisible and secret signal, called watermark,
is added to the host data. With the help of this watermark
issuer of the data can be unveiled, unauthorised users can be identified,
illicit copying can be avoided, any attempt to temper with the data can
be detected and many other security services can be provided. In this
thesis, the relations and differences between watermarking and communication
systems are elaborated. Based on these results new methods
for both watermarking and communication are derived.
A new blind, robust and reversible watermarking scheme based on
Code Division Multiple Access (CDMA) is presented in this thesis. Using
this scheme watermark is arithmetically added to spatial domain or
frequency domain. Watermark is extracted by using spreading codes
only. Proposed watermarking scheme is simple, computationally efficient
and can be applied to any image format.
A novel idea that watermark can be part of the image is presented. By
using watermark, which is a part of an image, digital watermarking can
be used beyond simple security tasks. A part of an image is selected
and embedded in the whole image as watermark. This watermarked
image is attacked (transmitted or compressed). By using the extracted
watermark and attacked selected part image quality can be assessed or
jpeg quantization ratio can be estimated or even image can be equalized
blindly.
Furthermore, CDMA based watermarking is used to authenticate radio
frequency signal. Spreaded watermark is added in the form of noise
to the modulated radio frequency signal. If this noise is increased,
watermarked signal automatically becomes a scrambled signal. Later
watermark is extracted and by using reversibility of proposed scheme
watermark is removed. Once the watermarked is removed original signal
is restored, hence descrambled.
Description
Table of contents
Keywords
authentication, CDMA, DCT, DWT, scrambling, security, watermarking