# A Comparative Analysis of Arabic Text Steganography
## 4 Arabic Text Steganography
### Hybrid Approach  
A combined or hybrid method involves the integration of two or more text steganography methods. The earliest proposal in this method [108] merges two methods: The Unicode method (whitespace) and the kashida method. The integrated technique embeds secret bit \"1\" by inserting whitespace. Before moving to the next word, it adds two consecutive whitespaces between words to hide \"1.\" In the case of secret bit \"0,\" there is no addition of kashida and whitespace. Later, merging Unicode with diacritics was suggested [109] to hide the confidential message. This method employs RNA to encode the secret messages, while non-printed \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Authors** & **Methodology** & **Pros** & **Cons** \\ \hline \multirow{4}{*}{[104]} & Each sharp edge in character & & \\  & embeds one bit, \"0” or \"1.\" & & \\  & Generates reference table for & & \\  & secret bit/s place. & & \\  & The number of sharp edges in & & \\  & each character is utilized to & & \\  & protect the same number of & & \\  & secret bits by converting it to & & \\  & decimal. It generates a code & & \\  & sequence of decimal numbers. & format. & \\  & Each sharp edge, dot, and & & \\  & typographical proportion can & & \\  & hide “0” or “1.” & & \\ \hline \hline \end{tabular}
\end{table} 
Table 16: A summary of the reviewed article on the sharp edges approach. \begin{table}
\begin{tabular}{c c c c} \hline \hline The verse & & & \\   How it is pronounced & & & \\   The corresponding feet & & & \\   Binary representation & 011011 & 0101011 & 0101011 & 011011 & 0101011 & 0101011 & 1011 \\   Its classification & & & Al-Taweel meter & \\ \hline \hline \end{tabular}
\end{table} 
Table 17: An example of a verse of an Arabic poem and how it is classified into poetry meters (Adapted from [107]). \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Author** & **Methodology** & **Pros** & **Cons** \\ \hline \multirow{4}{*}{[107]} & This method & & \\  & represented the poetry & & \\  & meters into binary & & \\  & representation to hide & & \\  & the secret bits. & & \\ \hline \hline \end{tabular}
\end{table} 
Table 18: A summary of the reviewed article on the poetry approach. characters are used to conceal these codes. Compression is applied by modifying the Run Length Encoding (RLE) compression algorithm to overcome its limitation. Similarly, the authors of [110] compressed secret messages using Gzip and encrypted these compressed secret messages by deploying AES. The embedding method employs two stego options of \"kashida\" and changes the Unicode of the letter based on the proposed blood group algorithm's behavior. Next, kashida and diacritics were combined [111] to cover the mystery message. The embedding algorithm conceals one part by adding Fathah, and the rest hides \"0.\" The other part adds two consecutive kashidas to hide \"1\" and one kashida to hide \"0.\"  
Again, kashida and Unicode methods were used by the authors of [112] to cover the confidential information. For the Unicode method, three small spaces (thin, hair, and Six-PRE-EM) were utilized. The presented scheme grouped the bitstream into 4 bits each. The first bit indicates kashida, where it inserts kashida to hide \"1\" and considers an existing kashida to hide \"0.\" The second bit indicates thin space, the third shows hair space, and the last bit indicates Six-PRE-EM. The existence of the three small spaces hides \"1\" while their absence hides \"0.\"  
The merger of counting-based secret sharing and kashida that was recently presented by the authors of [113] hides the secret sharing bits within Arabic text using kashida. Recently, Medium Mathematical Spaces (MSPs), ZWJ, JWJN and kashida were united [114] to protect the secret bits. The study hid one secret bit by changing format or including one whitespace or kashida. It can be observed from Table 19 that hybrid Arabic text steganography methods, using kashida and several kinds of spaces to hide the secret bit, have recently received more attention.