12#IMAGE AUTHENTICATION A FEW APPROACHES USING DIGITAL WATERMARKING

ABSTRACT

You thought images that you pick up are all yours? Think again, they may be secure enough with a Watermark that could be very well traced down.

A digital Watermark is a digital signal or pattern inserted into a digital image. Since this signal or pattern is present in each unaltered copy of the original image, the digital Watermark may also serve as a digital signature for the copies. The desirable characteristics of a Watermark are

· Watermark should be resilient to standard manipulations of any nature.

· It should be statistically irremovable

Every Watermarking system consists at least two different parts:

· Watermark Embedding Unit

· Watermark Detection and Extraction Unit

In this paper, we discuss an algorithm for embedding and detecting the Watermark in a still image. A robust, secure, invisible Watermark is imprinted on the image I, and the Watermarked image WI, is distributed. The author keeps the original image I. To prove that an image WI' or a portion of it has been pirated, the author shows that W' contains his Watermark (to this purpose, he could but does not have to use his original image I). The best a pirate can do is to try to remove the original W Watermark (which is impossible if the Watermark is secure).

There can be another way out for the pirate, as to embed his signature in the image. But this does not help him too much because both his "original" and his Watermarked Image will contain the author's Watermark (due to robustness property), while the author can present an image without pirate's Watermark. Thus, the ownership of the image can be resolved in the court of law.

We have done the implementation in MATLAB and doing the simulation in C++..