VOL. 10, NO. 3, FEBRUARY 2015 ISSN 1819-6608 ARPN Journal of Engineering and Applied Sciences © 2006-2015 Asian Research Publishing Network (ARPN). All rights reserved. www.arpnjournals.com 1345 CAPACITY PERFORMANCE OF STEGANOGRAPHY METHOD IN TEXT BASED DOMAIN Baharudin Osman, Roshidi Din and Mohd Rushdi Idrus School of Computing, College of Arts and Sciences, Universiti Utara Malaysia, UUM Sintok, Kedah, Malaysia E-Mail: bahaosman@uum.edu.my ABSTRACT Capacity is one of the performance factors in embedding process of any text steganography methods. A better embedding ratio and saving space ratio offers more text can be hidden inside cover text. This paper tries to evaluate several format based techniques of text steganography based on their embedding ratio and saving space capacity factors. This paper analysed the performance of text steganography methods which are changing in Alphabet Letter Patterns (CALP), Vertical Straight Line (VERT) and Quadruple Categorization (QUAD) methods based on these two factors. Embedding Ratio (ER) and Saving Space Ratio (SSR) is used to measure the performance. It has been identified that VERT method give a good effort performance compared to CALP and QUAD based method. In future, a robustness of text steganography methods should be considered as a next effort in order to find a strength capability on text steganography. Keywords: text steganography. embedding ratio, saving space ratio, CALP, QUAD. VERT. INTRODUCTION Steganography is the arts of science to hide data in a cover media such as text, audio, video and image which is one of sub disciplines in information security field. It is the most popular sub disciplines amongst others such as anonymity, copyright marking and covert channel (Fabien, Petitcolas, Ross & Markus, 1999), (Al-Mualla & Al-Ahmad, 2013). Steganography has played a major significant role in secret communication such as e-national security (Si and Li, 2008), e-military (Din & Azman, 2009), multimedia property (Yusuf, Firoj & Asif, 2012), authentication (Gunawardena, Kulkarni & Gnanasekaraiyer, 2013) etc. Various applications have been implemented in steganography (Hamid et al., 2012), (Kodovsky, Jessica & Vojtech, 2012), (Wang & Jiangqun, 2012). Steganography differs from cryptography which it scrambles messages so they cannot be understood. In short, cryptography is about protecting the content of messages whereas steganography is about concealing the existing messages. Table-1 shows the advantages and disadvantages of both technologies. Table 1: Comparison between steganography and cryptography (Kaur, Pooja & Harish, 2013), (Vahedi, Vincent & Ian, 2014). Steganography is the science of hiding information with the goal is to hide the data from a third party in such way that no one suspects the existence of the message. The word steganography is derived from Greek (steganos + graphy) and it means covered or hidden writing. Actually, steganography is introduced to hide the existence of the communication by concealing a hidden message in an appropriate carrier which is divided into two domains such as technical steganography (image, audio, video, and network packet etc.) and natural language steganography. There are two aspects of steganography, namely digital steganography and natural language steganography. Digital steganography concentrates on channel capacity which is concerned about a cover medium to hide messages, while natural language steganography concentrates on using written natural language to conceal secret messages (Kaur, Pooja & Harish, 2013). Digital steganography has been carried out on image steganography (Hamid et al., 2012), (Wang & Jiangqun, 2012), (Choudhary, 2013), audio steganography (Zamani, Azizah &Shahidan, 2012), (Nutzinger, 2012), (Adhiya & Swat, 2012), and video steganography (Cao, Xianfeng & Dengguo, 2012), (Bodhak, & Baisa, 2012), (Dasgupta, Mandal & Paramartha, 2012). which have produced good results. Besides, several efforts on steganography system based on digital steganography for hidden and unhidden messages such as Outguess, F5, YASS and MBS (Hamid et al., 2012), (Kodovsky, Jessica & Vojtech, 2012), (Wang & Jiangqun, 2012), (Choudhary, 2013) have also been developed. Natural language steganography is the art of using natural language to conceal secret message (Mansor, Din & Azman, 2010). Currently, there are two groups of natural language steganography environment namely text steganography, and linguistic steganography (Baharudin et al, 2013), (Din, 2014), (Din, Che Ani & Azman, 2012), (Kaleem, 2012). Several types of text steganography methods which are line-shift coding, word-shift coding (Singh, Rajat & Agarwal, 2012), (Sharma & Shweta, 2013) and feature coding (Govada et al., 2012), (Majercak et al., 2013), (Chhikara & Latika, 2013) have been explored.