# A Comparative Analysis of Arabic Text Steganography
## 4 Arabic Text Steganography
### Sharp Edges Approach  
The algorithms suggested by the authors of [104] involve using Arabic letters' sharp edges to hide the secret bits. Each letter hides secret bits based on the number of its sharp edges, as shown in Figure 4. For example, a letter with one sharp edge is probable to embed one secret bit 0 or 1. The authors of [104] designed a reference table to keep the locations of secret bits in the cover letter.  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Authors** & **Methodology** & **Pros** & **Cons** \\ \hline
[97] & Inserts normal space after pseudo & & \\  & space to hide “1.” No insertion & & \\  & hides “0.” & & \\  & & computational time. & \\
[99] & The shape’s code hides “1” and & & \\  & representative letter’s code hides “0.” & & \\  & & & \\  & The Arabic character \(\leftrightarrow\)\(\Rightarrow\) or “ \(\leqslant\)” & & \\  & hides “1” and the Persian character \(\leftrightarrow\) & & \\  & \(\bigtriangleup\)” or “ \(\leqslant\)” & \(\wp\)” hides “0.” & & \\  & & & \\  & The special form of the word “La” & & \\  & hides “1” and the normal form & & \\  & & hides 0. & \\  & & & \\  & Changes the Unicode of Arabic & & \\  & isolated letter to hide “1” and leaves & & \\  & it unchanged to hide 0. & & \\  & & & \\  & & & \\  & & \\  & & & \\  & & & \\  & & \\  & & & \\  & & & \\  & & \\  & & & \\  & & \\  & & & \\  & & \\ \end{tabular}
\end{table}
Table 13: A summary of the reviewed articles on the Unicode method.  
The approach described by the authors of [105] operates on dotted and undotted alphabets. Random numbers are generated and used to assign alphabets sufficient for hiding 104 bits of secret message. This results in the following alphabets:  
The number of sharp edges on the initial alphabet, as shown in in Table 14, determines the number of bits that will be hidden. The secret bit that corresponds to this number is included in the code sequence, and the process continues until all the bits are embedded. For instance, the character (\(\jmath\)) has two sharp edges. Hence, it can carry the first two binary bits (i.e., 01) and represent them in the corresponding decimal unit, which is 1.  
The sharp edges with dots and typographical proportion of Arabic letters were presented by the authors of [106]. The presented algorithm, called the Primitive Structural algorithm, gives each letter more than one potential position to embed the secret bits, as shown in Table 15. At the same time, each letter carries more hidden bits than the method in [106].  
From Table 16 it can be summarized that the serious limitation of the sharp edges method is security. Thus, it requires further security layers to secure the indications of the concealed bits in the stego file. Nevertheless, the sharp edges method achieves better embedding capacity.  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Char**} & \multirow{2}{*}{**Unicode**} & \multicolumn{2}{c}{**Primitive Structural**} & \multirow{2}{*}{**Num. of Potential**} \\  & & \multicolumn{2}{c}{**Method Entities**} & \\ \hline  & & **Sharp-Edges** & **Dot(s)** & **Typographical** & **Hiding Places** \\ \hline \(\uparrow\) & \(\backslash\)U0627 & 2 & 0 & 1 & 3 \\ \(\searrow\) & \(\backslash\)U0628 & 2 & 1 & 3 & 6 \\ \(\searrow\) & \(\backslash\)U062A & 2 & 2 & 3 & 7 \\ \(\searrow\) & \(\backslash\)U062B & 2 & 3 & 3 & 8 \\ \(\mathfrak{C}\) & \(\backslash\)U062C & 3 & 1 & 5 & 9 \\ \hline \hline \end{tabular}
\end{table}
Table 15: Number of sharp edges for each letter (Adapted from [107]).  
Figure 4: Arabic characters’ sharp edges (Adapted from [105]).