VOL. 11, NO. 1, JANUARY 2016 ISSN 1819-6608 ARPN Journal of Engineering and Applied Sciences ©2006-2016 Asian Research Publishing Network (ARPN). All rights reserved. www.arpnjournals.com 421 SURVEY ON RELATIONAL DATABASE WATERMARKING TECHNIQUES Abd. S. Alfagi 1 , A. Abd. Manaf 1 , B. A. Hamida 2 , S. Khan 2 and Ali A. Elrowayati 3 1 Advanced Informatics School, Universiti Teknologi Malaysia, Kuala Lumpur, Malaysia 2 Department of Electrical and Computer Engineering, International Islamic University Malaysia, Kuala Lumpur, Malaysia 3 Faculty of Electrical and Electronic Engineering, Universiti Tun Hussein Onn Malaysia, Malaysia ABSTRACT Digital watermarking has been in multimedia data use over the past years. Recently it has become applicable in relational database system not only to secure copyright ownership but also to ensure data contents integrity. Further, it is used in locating tampered and modified places. However, the watermarking relational database has its own requirements, challenges, attacks and limitations. This paper, surveys recent database watermarking techniques focusing on the importance of watermarking relational database, the difference between watermarking relational database and multimedia objects, the issues in watermarking relational database, type of attacks on watermarked database, classifications, distortion introduced and the embedded information. The comparative study shows that watermarking relational database can be an effective tool for copyright protection, tampered detection, and hacker tracing while maintaining the integrity of data contents. In addition, this study explores the current issues in watermarking relational database as well as the significant differences between watermarking multimedia data and relational database contents. Finally, it provides a classification of database watermarking techniques according to the way of selecting the candidate key attributes and tuples, distortion introduced and decoding methods used. Keywords: database watermarking, digital watermarking, watermarking techniques, attacks, relational databases. INTRODUCTION Many applications provide a wide range of web- based services such as database, digital libraries, digital repositories, health services, and e-commerce, etc. These applications aim to make the digital assets secured, easily retrievable; making sure data is archived properly and shared electronically [1]. Consequently, more challenging issues of data piracy, tampering, copyrighting, ownership claiming, illegal redistribution, and data integrity checks arise. These issues are the main concern of data owners, though several security mechanisms have been deployed for database protection of access control and encryption. However, those security mechanisms protect the exposure of sensitive information before accessing that information [2]. Once the data is accessed the data is no longer protected against tampering, copyrighting, and illegal redistribution [3]. Therefore, digital watermarking techniques are studied here from viewpoint of deter piracy, tampering, copyrighting, ownership proof, and data integrity check [4-6]. DIGITAL WATERMARK Digital watermark is a piece of information inserted into data for copyright protection, proof of ownership, traitor tracing, and integrity check. Generally, watermarking system consists of two phases, namely, watermark embedding and extraction as shown in Figure- 1. In the embedding phase, a watermark information (W) is securely inserted into the original database using secret key (K). Then the watermarked database becomes ready for publication or distribution. The extraction phase is important to verify the originality and integrity of database. In this phase, the watermarked database is taken as input for extracting the watermark information using same key. The extracted watermark is compared with the original watermark information to verify the ownership of a suspicious database [7-9] or to protect the copyright [10- 12]. A watermark detection process can be applied to any database so as to determine whether or not a legitimate watermark can be detected [13]. Figure-1. Basic framework for watermarking system [13]. IMPORTANCE OF WATERMARKING DATABASE Digital watermarking is important in many real life applications for proof data ownership, protect copyright, fingerprinting data, and to preserve relational database integrity [15-17]. In ownership proof, data owners can securely insert a watermark into a relational database using secret key before publishing or distributing their data. At the extraction phase, the data owners can demonstrate the presence of their watermark in order to verify third party ownership claiming. Similarly, for copyright protection, data owners securely embed owner’s specific information (e.g. image, text, speech etc.) into the relational database in order to prevent others from claiming copyright [18]. In the fingerprinting data, the