Adnan Gutub, Lahouari Ghouti, Yousef Elarian, Sameh Awaideh, Aleem Alvi Kuwait Journal of Science & Engineering (KJSE), Vol. 37, No. 1, June 2010 Utilizing Diacritic Marks for Arabic Text Steganography ADNAN A. GUTUB 1 , LAHOUARI M. GHOUTI 2 , YOUSEF S. ELARIAN 2 , SAMEH M. AWAIDEH 2 , ALEEM K. ALVI 2 1 Center of Excellence in Hajj and Omrah Research, Umm Al-Qura University, Makkah, Saudi Arabia. Associate Researcher, Center Of Excellence in Information Assurance (CoEIA), King Saud University, Riyadh, Saudi Arabia. Email: aagutub@ uqu.edu.sa 2 College of Computer Sciences and Engineering, King Fahd University of Petroleum & Minerals, Dhahran 31261, Saudi Arabia. ABSTRACT Arabic diacritic marks represent efficient carriers to hide information in plain text. The ability of diacritics to be invisibly superimposed on each other when typed multiple times consecutively makes them suitable for robust data-hiding applications. In this paper, we propose two different algorithms to map secret messages into repeated diacritics in a non-wasteful fashion, where the number of extra diacritics is defined in fixed and variable size fashions. Therefore, the size of the outputted text is decided by the encoding flexibility. Both steganographic algorithms are characterized by several advantages over their existing counterparts. Finally, we provide a detailed performance analysis of both algorithms in terms of embedding capacity, robustness and file-size measures. Keywords: Arabic text; capacity; data hiding; diacritic marks; steganography. INTRODUCTION Since ancient times, people have recognized the importance of information (and communication) secrecy and security. Since then, several approaches have been successfully adopted and used for covert communications and information exchange. Steganograhy, or the art of covert writing, has emerged as the most efficient means for such purposes in hostile situations such as wartime. As such, steganograhy aims at concealing the very existence of the covert messages from enemies, attackers and hackers alike which would ensure the secrecy, and hence the security, of these covert messages. The “plain messages” (or "plaintext" in cryptography) are discreetly manipulated to seamlessly carry the secret (or covert) messages. Moreover, nowadays with the emergence of the Internet, the Global Information Highway, steganography has been the focus of active research to develop novel and innovative techniques to serve such purposes. Figure 1, as represented by Dmitri (2007), gives an outline where a detailed hierarchical classification of steganography is given.