Digital Watermarking Algorithm Using LSB Abdullah Bamatraf Information Technology and Multimedia Faculty Tun Hussein Onn University, Malaysia abdom45@hotmail.com Rosziati Ibrahim Information Technology and Multimedia Faculty Tun Hussein Onn University, Malaysia rosziati@uthm.edu.my Mohd. Najib B. Mohd Salleh Information Technology and Multimedia Faculty Tun Hussein Onn University, Malaysia najib@uthm.edu.my Abstract__ In this paper, a simple and robust watermarking algorithm is presented by using the third and the fourth least significant bits (LSB) technique. The proposed algorithm is more robust than the traditional LSB technique in hiding the data inside the image. Using the proposed algorithm, we will embed two bits in the third and fourth LSB. Experimental results show that the quality of the watermarked image is higher. Key Words: Digital watermarking, Grayscale images, secret data, LSB, PSNR. 1. INTRODUCTION Illegal copying, modifying, tampering and copyright protection have become very important issues with the rapid use of internet [7]. Hence, there is a strong need of developing the techniques to face all these problems. Digital watermarking [1] emerged as a solution for protecting the multimedia data. Digital Watermarking is the process of hiding or embedding an imperceptible signal (data) into the given signal (data). This imperceptible signal (data) is called watermark or metadata and the given signal (data) is called cover work. The watermark should be embedded into the cover work, so that it should be robust enough to survive not only the most common signal distortions, but also distortions caused by malicious attacks. This cover work can be an image, audio or a video file. A watermarking algorithm consists of two algorithms, an embedding and an extraction (or detection) algorithm. The idea of watermarking first appeared hundreds of years ago [2]. Watermarking technology was used to mark information authenticity by many different means. Watermarking technology has been used in computer as well. Most of the work on computer watermarking technology was for embedding a watermark into images, audio, and video files. Media watermarking research is a very active area and digital image watermarking became an interesting protection measure and got the attention of many researchers since the early 1990s [3]. The rest of this paper is organized as follows: Section 2 describes the related work and Section 3 discusses the proposed algorithm. Results and discussion is given in Section 4 and finally, conclusion will be presented in Section 5. 2. RELATED WORK In this section a literature review of digital watermarks used for images is presented. It describes the previous work which had been done on digital watermarks, including the analysis of various watermarking schemes and their results. Ersin Elbasi et al [4] embed the watermark in a tree structure in the Discrete Wavelet Transform domain. For watermark embedding, the two level DWT decomposition of an NxN gray scale image I is computed. The same PRN sequence is embedded into the DWT coefficients higher than a given threshold T1 in the LL2 and HH2 bands. The watermark is also embedded into the children of DWT coefficients. The original DWT coefficients are replaced by the modified DWT coefficients. The final step is to compute the inverse DWT to obtain the watermarked image I'. For watermark detection, the DWT of the watermarked and possibly attacked image I* is computed. All the DWT coefficients higher than a given threshold T2 in the LL2 and HH2 bands are selected. Then the sum Z of all attacked DWT coefficients multiplied by either the embedded watermark or other random PRN sequence is computed, divided by the length of the PRN sequence. The sum is also computed for the children of modified DWT coefficients. A predefined threshold T is chosen for LL2 and HH2 bands and the HH1 band. In each band, if Z exceeds T, the conclusion is that the watermark is present. Gil-Je Lee et al [5], presented a simple and robust watermarking scheme by using random mapping function. The idea of the proposed algorithm is watermark embedding which can be more robust than the traditional 2010 International Conference on Computer Applications and Industrial Electronics (ICCAIE 2010), December 5-7, 2010, Kuala Lumpur, Malaysia 978-1-4244-9055-4/10/$26.00 ©2010 IEEE 155