Digital Watermarking: Digital Data Transfer

CHAPTER 1

INTRODUCTION

Nowadays internet and related technologies are growing rapidly. At the same time, the security is a major issue in the digital data transfer. There are lots of methods are used that. Watermarking is one of the methods for ensuring security. Experts are still facing lots of technical challenges in copyright management and protection of intellectual property rights. Watermarking provides a solution for secure transfer of multimedia content and images. Since few decades, watermarking is researched extensively in the security area of digital image technology, especially in still images. Watermarking is a process of embedding specific information into the content, without altering the basic information. All watermarking processes

At the receiver stage the input may be image, key, watermark or original image and the output is a watermark or some kind of credibility value that denote the possibility of the data having a given watermark. During the transmission of the watermarked content it may passes through different types of attacks. The best watermarking is the one which can withstand this different types attacks. If the extracted watermark is compare with the original watermark at the receiving end, then this type of watermarking is known as the non-blind watermarking and if the original watermark is not used at the receiver is known as the blind watermarking.

2. TYPES OF WATERMARKING Here a brief reviews about various watermarking techniques are explained, which deals with the protection of digital content. The algorithms described in this section are applied to gray scale images but most of the techniques can be extended to color images by embedding watermark in the luminance channel. The watermarking techniques to be presented in this section are categorized based on following criterion.

2.1. According to watermarking

[3] define robustness as the “ability to detect the watermark after common signal processing operations”. In other words, embedded watermark should be hard to detect, remove, or replace by illegal sources without degrading the quality of the content to very low such that it becomes unusable. Music, images and video signals may undergo many types of distortions. Lossy compression like many other signal transformations are also common. For example, an image might be contrast enhanced and colors might be altered somewhat, or an audio signal might have its bass frequencies amplfied. In general, a watermark must be robust to transformations that include common signal distortions as well as digital-to-analog and analog-to-digital conversion and lossy compression. Moreover, for images and video, it is important that the watermark survive geometric distortions such as translation, scaling and