International journal of computer science & information Technology (IJCSIT) Vol.2, No.5, October 2010 DOI : 10.5121/ijcsit.2010.2507 91           Pranab Kumar Dhar *1 , Mohammad Ibrahim Khan 2 and Saif Ahmad 3 Department of CSE, Chittagong University of Engineering and Technology, Bangladesh 1 pranab_cse@yahoo.com 2 muhammad_ikhancuet@yahoo.com 3 saeef.cse05@yahoo.com ABSTRACT Digital watermarking plays an important role for protecting digital contents from unauthorized copying. This paper proposes a new audio watermarking method based on Discrete Cosine Transformation (DCT) for copyright protection. In our proposed watermarking method, the original audio is transformed into DCT domain. The absolute values of DCT coefficients are divided into an arbitrary number of segments and the energy of each segment is calculated. Watermarks are then embedded into the selected peaks of the highest energy segment. Watermarks are extracted by performing the inverse operation of watermark embedding process. Simulation results indicate that our proposed watermarking method is highly robust against various kinds of attacks such as noise addition, cropping, re-sampling, re-quantization, MP3 compression, and echo, and achieves similarity values ranging from 13 to 32. In addition, our proposed method shows SNR (signal-to-noise ratio) values ranging from 13 dB to 24 dB. KEYWORDS Copyright protection, Digital Watermarking, Discrete Cosine Transform, Sound Contents 1. INTRODUCTION Recent improvement in computational world and the proliferation of the Internet have facilitated the production and distribution of unauthorized copies of copyrighted digital contents. Consequently, the area of effective and efficient copyright protection is a field of interest of the worldwide scientific communities. Digital audio watermarking has drawn extensive attention for copyright protection of audio data. A digital audio watermarking is a process of embedding watermarks into audio signal to show authenticity and ownership. Audio watermarking should meet the following requirements :(a) Imperceptibility: the digital watermark should not affect the quality of original audio signal after it is watermarked; (b) Robustness: the embedded watermark data should not be removed or eliminated by unauthorized distributors using common signal processing operations and attacks; (c) Capacity: capacity refers to the numbers of bits that can be embedded into the audio signal within a unit of time; (d) Security: security implies that the watermark can only be detectable by the authorized person. All these requirements are often contradictory with each other. However, it should satisfy the important properties such as imperceptibility and robustness. In this paper, we propose a new watermarking method using Discrete Cosine transformation (DCT) for audio copyright protection. The watermarks are embedded into the selected prominent peaks of the highest segment of absolute DCT coefficients. Experimental results indicate that the proposed watermarking method provides strong robustness against several kinds of attacks such as noise addition, cropping, re-sampling, re-quantization, MP3 * Corresponding author