Improved capacity Arabic text watermarking methods based on open word space

Digital watermarking is used to protect text copyright and to detect unauthorized use. In this paper, two invisible blind watermarking methods for Arabic text are proposed. Since the pseudo-space is very small space used to force the connected characters to be isolated, it is added to the word space to hide binary bit ‘‘0” or ‘‘1”. In the first proposed method, the pseudo-space is inserted before and after normal word space based on dotting feature in Arabic text. The second proposed method inserts the pseudo-space and other three small or zero width spaces to increase the capacity, where the presence of them indicates bit ‘‘1” and the absence indicates bit ‘‘0”. The comparative results obtained by testing the proposed methods with some of existing watermarking methods using variable size text samples with different watermark lengths. The experiments show that the proposed methods have the highest capacity and higher imperceptibility than other watermarking techniques from the literature. The robustness of the proposed methods is tested under most of possible text attacks. They are robust against electronic text attacks such as: copying and pasting, text formatting and text tampering for tampering ratio up to 84%.