  / ;/ 8      / ;/ 8      / ;/ 8      / ;/ 8    /     /     /     /     Pranab Kumar Dhar (1) , Mohammad Ibrahim Khan (1) and Sujan Chowdhury (1) 1. Department of Computer Science and Engineering, Chittagong University of Engineering and Technology. Email: pranab_cse@yahoo.com, muhammad_ikhancuet@yahoo.com, sujan_cse_04@yahoo.com ABSTRACT Digital watermarking has drawn extensive attention for copyright protection of multimedia data. This paper proposes a new watermarking system for digital images using efficient systematic linear block codes (SLBC) in discrete cosine transform (DCT) domain. The proposed watermarking system using SLBC generates a code sequence of {0, 1} that provides error correction capabilities and then replaces it with a binary watermark sequence of {1, 1}. This achieves more robust invisible image watermarks and requires a small storage unit for binary sequence numbers. The generated watermark sequence is then used as an input for our proposed watermarking system which consists of watermark embedding process and watermark detection process. Experimental results indicate that the invisible watermark embedded with the proposed system are very robust against various kinds of attacks such as white Gaussian noise, JPEG compression, median, and mean filtering, by showing similarity values ranging from 0.7 to 0.8. KEY WORDS: Digital Watermarking, Linear Block Code, Copyright Protection. 1.0 INTRODUCTION In recent years, rapid development of information technology and computer networks, the privacy of copyrighted digital data has become an important issue in the digital industry. Multimedia data such as audio, video or image can be easily distributed over the Internet. However, many publishers may be reluctant to show their work on the Internet because multimedia data can be easily duplicated without the owner’s consent. In order to overcome this copyrightprotection issue, digital watermarking techniques have received considerable attentions. A digital watermark is an invisible signature embedded inside an image to show the authenticity and ownership. An effective digital watermark should be perceptually invisible to prevent obstruction of the original image. It should also be robust against many image manipulations, such as filtering, noise attack, and compression. A significant number of watermarking techniques have been reported in recent years. Some methods embed the watermark in the spatial domain of an image [12] . Other watermarking techniques use transform methods, such as the fast Fourier transform (FFT) [3] , discrete cosine transform (DCT) [46] , to embed the watermark. Recent implementations have also used the human visual system (HVS) to improve the watermark performance [78] . In this paper, we propose efficient systematic linear block codes (SLBC) for the invisible image watermarking in the DCT domain. SLBC has been widely used in digital communication since it performs well for error correction when information is transmitted over a noisy channel [10] . However, SLBC generates a code sequence of {0, 1} which is not effective for embedding in DCT components since the watermark 0’s cannot change the DCT components in (5) on Section 3.1. Thus, we replace the code sequence of {0, 1} with a binary watermark sequence of {1, 1} which not only provides robustness to generate new watermarked DCT coefficients but also requires minimal storage for binary sequence numbers. The generated watermark sequence is then used as an input for our proposed watermarking system which consists of watermark embedding process and watermark detection process. Simulation results indicate that our proposed system shows strong robustness against several image processing attacks such as white Gaussian noise, JPEG compression, median, and mean filtering. It achieves similarity values ranging from 0.7 to 0.8. The rest of the paper is organized as follows. Section 2 discusses the background information regarding linear block code, generator matrix, and error correction using SLBC. Section 3 introduces our proposed watermarking system including watermark embedding process and watermark detection process. Section 4 presents our experimental results, and finally section 5 concludes this paper.