Hybrid DCT-DWT Watermarking and IDEA Encryption of Internet Contents M.A. Mohamed and A.M. El-Mohandes Electronics and Communication Engineering, Faculty of Engineering-Mansoura University Mansoura, Dakhlia, Egypt [[ Abstract Encryption and watermarking are complementary lines of defense in protecting multimedia content. Recent watermarking techniques have therefore been developed independent from encryption techniques. In this paper, we present a hybrid image protection scheme to establish a relation between the data encryption key and the watermark. Prepositioned secret sharing allows the reconstruction of different encryption keys by communicating different activating shares for the same prepositioned information. Each activating share is used by the receivers to generate a fresh content decryption key. In the proposed scheme, the activating share is used to carry copyright or usage rights data. The bit stream that represents this data is also embedded in the content as a visual watermark. When the encryption key needs to change, the data source generates a new activating share, and encrypts the corresponding data with the key constructed from the new activating share. Before transmission, the encrypted data is embedded in a multimedia stream. Each receiver can extract the encrypted data from the host image, and decrypt this data after reconstructing the same key. Our presentation will include the application of the scheme to a test image, and a discussion on the data hiding capacity, watermark transparency, and robustness to common attacks. Keywords: discrete cosine transform, discrete wavelet transform, and international data encryption algorithm (IDEA), Bit correct ratio. 1. Introduction The advent of the Internet has resulted in many new opportunities for the creation and delivery of content in digital form. Applications include electronic advertising, real-time video and audio delivery, digital repositories and libraries, and Web publishing. An important issue that arises in these applications is the protection of the rights of all participants [1], [2]. It has been recognized for quite some time that current copyright laws are inadequate for dealing with digital data. This has led to an interest towards developing new copy deterrence and protection mechanisms. One such effort that has been attracting increasing interest is based on digital watermarking techniques [3]. Digital watermarking; Fig.1, is the process of embedding information into digital multimedia content such that the information (which we call the watermark) can later be extracted or detected for a variety of purposes including copy prevention and control. Digital watermarking has become an active and important area of research, and development and commercialization of watermarking techniques is being deemed essential to help address some of the challenges faced by the rapid proliferation of digital content [4]. A secure computing environment would not be complete without consideration of encryption technology; Fig.2. The term encryption refers to the practice of obscuring the meaning of a piece of information by encoding it in such a way that it can only be decoded, read and understood by people for whom the information is intended. It is the process of encoding data to prevent unauthorized parties from viewing or modifying it. The use of simple codes to protect information can be traced back to the fifth century BC. As time has progressed, the methods by which information is protected have become more complex and more secure. Encryption can be used to provide high levels of security to network communication, e-mail, files stored on hard drives or floppy disks, and other information that requires protection. Encryption and watermarking each provide a different line of defense in protecting content. Recent research has therefore followed two different avenues resulting in encryption techniques that are independent from watermarking techniques: (i) Encryption makes the content unintelligible through a reversible mathematical transformation based on a secret key [1], [2]. In secure multimedia content distribution, the audio/visual stream is compressed, packetized and encrypted [3]. One of the most challenging problems in distribution architectures is the delivery of the decryption key, and (ii) Watermarking (data hiding) [4] – [7] is the process of embedding data into a multimedia element such as image, audio or video. This embedded data can later be extracted from, or detected in, the multimedia element for different purposes such as copyright protection, access control, and broadcast monitoring. One possible avenue of research is to establish a relation between the data encryption key and the watermark. A recent method for delivering the keying information in secure multimedia multicast applications suggests the use of a media dependent channel [2]. The rekey messages are embedded in the multimedia stream rather than being sent in a separate channel. IJCSI International Journal of Computer Science Issues, Vol. 9, Issue 1, No 2, January 2012 ISSN (Online): 1694-0814 www.IJCSI.org 394 Copyright (c) 2012 International Journal of Computer Science Issues. All Rights Reserved.