SHORT PAPER International Journal of Recent Trends in Engineering, Vol. 1, No. 1, May 2009 508 Pioneering the Technique for Invisible Image Watermarking on Color Image Soumik Das 1 , Pradosh Bandyopadhyay 2 , Shauvik Paul 3 , Arindam SinhaRay 4 & Dr.Monalisa Banerjee 5 Techno India/MCA, Salt Lake, India Email: 1 soumikdas.techno@yahoo.co.in Email: 2 bandyopadhyay_pradosh@rediffmail.com, 3 paulshauvik@yahoo.co.in, 4 arindam.sinharay@gmail.com, 5 monalisa_erjee@yahoo.com Abstract— Accessibility and ease of internet, together with availability of relatively inexpensive digital recording and storage devices has created an environment where duplication, unauthenticated use and maldistribution of digital content has become very easy. This also facilitates unauthorized use, misappropriation, misrepresentation. Thus authentication of multimedia contents (such as image, video, audio) has achieved a sharp attention in recent times. In this perspective we’ve already introduced a framework for invisible image watermarking for color image authentication. In this paper we propose a method for embedding color watermark image to color host image in a more efficient manner. We introduce a new arena of embedding color watermark image at LSB to different positions of color host image in this paper. In proposed watermarking framework, it allows a user with an appropriate secret key and a hash function to verify the authencity, integrity and ownership of an image. We’ve used blind extraction method. I. INTRODUCTION igital Watermarking is the process of embedding information into a digital signal. A watermarking approach provides a persistent link between the authenticator and the content it authenticates. [1] The Digital Image Watermarking (will be referred to as watermarking for rest of the paper) can be classified into two categories - Visible Watermarking and Invisible Watermarking [4], as well as Fragile and Semi fragile watermarking. Our focused area is Invisible Fragile Watermarking. In this kind of watermarking the information is added as digital data to the original, but it can not be perceived as such. Moreover it is highly sensitive to any type of data alteration and tampering can easily be detected [2]. At best to our knowledge we are pioneering the technology which can embed a color watermark image in a color host image. In this sort of watermark, our proposal with 2-bit LSB’s scheme (will be referred to as 2-bit scheme for rest of the paper) is already accepted [8]. In this paper we’ve improved our scheme to 1-bit LSB scheme (will be referred to as 1-bit scheme for rest of the paper) to achieve a much better result regarding PSNR value (Detailed Analysis is reported in the sub section B of Section III). Our proposed framework will ensure- 1] The extracted watermark remains intact. i.e., image authentication is guaranteed. 2] Quality of generated watermarked image is much improved. w.r.t. others. [5] 3] The security issues [3] related to the watermark by using a secret key and a hash function. In current communication, we’ve discussed the technique for embedding the watermark and technique for extraction of the watermark in Section II. We’ve reported experimental analysis in Section III and conclusions are made in Section IV. II. TECHNIQUE FOR EMBEDDING WATERMARK AND EXTRACTION OF WATERMARK With contrast to the previous one, a major improvement is being made in this paper. Our already proposed framework will extract two LSB’s of ‘Blue(B)’ value from each pixel of individual tiles of host image using a secret key and a hash function. Instead of embedding the watermark image at two LSB’s of ‘Blue’(B) value of each pixel of individual tiles, here we’ve taken only the LSB of ‘Blue’(B) value of each pixel of individual tiles of host image. As ‘Blue’ is less sensitive to Human Visual System (HVS) [5],[6], we are only manipulating the ‘Blue’ value. The ‘Red’ value and ‘Green’ value of color host image are getting unchanged. The comparative study of the algorithms for 2-bit scheme and 1-bit scheme is reported below. According to our proposed frame work minimum no. of host image block multiplied by no. of bit embedded should be equal to the bit size of RGB. If the size of host image is not sufficient for 1-bit scheme, we can easily apply 2-bit scheme because PSNR value for 2-bit scheme is also very good. Detailed analysis will be found in Section III. Here we’ve made a comparative study between our already proposed framework (2-bit scheme) [8] [9] and the new framework (1-bit scheme). A. Algorithm for Embedding Watermark using 1-bit Scheme: Let the color host image be ‘Y’. A color watermark ‘A’ will be inserted in it and again will be extracted from it for authentication. The color host image is divided into twenty-four equal blocks (Y i ), where each block size is same with color watermark ‘A’. In the following discussion, we concentrate on inserting and extracting some bit information of color watermark ‘A’ into the D © 2009 ACADEMY PUBLISHER