A VLSI ARCHITECTURE FOR VISIBLE WATERMARKING IN A SECURE STILL DIGITAL CAMERA (S2DC) DESIGN (CORRECTED)

INTRODUCTION

WATERMARKING is the process that embeds data called a watermark, a tag, or label into a multimedia object such that the watermark can be detected or extracted later to make an assertion about the object. The object may be an image, audio, video, or text. Whether the host data is in spatial domain, discrete cosine-transformed, or wavelet-transformed, watermarks of varying degree of visibility are added to present media as a guarantee of authenticity, ownership, source, and copyright protection. In general, any watermarking scheme (algorithm) consists of three parts, such as the following: 

1) watermark;

2) encoder (insertion algorithm);

3) decoder and comparator (verification or extraction or detection algorithm)

Whether each owner has a unique watermark or an owner wants to use different watermarks in different objects, the marking algorithm incorporates the watermark into the object. The verification algorithm authenticates the object determining both the owner and the integrity of the object. Watermarks and watermarking techniques can be divided into various categories. The watermarks can be applied either in spatial domain or in frequency domain. It has been pointed out that the frequency-domain methods are more robust than the spatial-domain techniques. On the other hand, the spatial domain watermarking schemes have less computational overhead compared with frequency-domain schemes. According to human perception, the digital watermarks can be divided into four categories:

1) visible; 

2) invisible-robust;

3) invisible-fragile;

4) dual. 

A visible watermark is a secondary translucent image overlaid into the primary image and appears visible to a casual viewer on careful inspection. The invisible-robust watermark is embedded in such a way that modifications made to the pixel value is perceptually not noticed, and it can be recovered only with appropriate decoding mechanism. The invisible-fragile watermark is embedded in such a way that any manipulation or modification of the image would alter or destroy the watermark. A dual watermark is a combination of a visible and an invisible watermark. In this type of watermark, an invisible watermark is used as a back-up for the visible watermark. 

VIDEO DEMO