UniSpaCh: a text-based data hiding method using unicode space characters

Lip Yee Por, Koksheik Wong, Kok Onn Chee

Research output: Contribution to journalArticleResearchpeer-review

89 Citations (Scopus)


This paper proposes a text-based data hiding method to insert external information into Microsoft Word document. First, the drawback of low embedding efficiency in the existing text-based data hiding methods is addressed, and a simple attack, DASH, is proposed to reveal the information inserted by the existing text-based data hiding methods. Then, a new data hiding method, UniSpaCh, is proposed to counter DASH. The characteristics of Unicode space characters with respect to embedding efficiency and DASH are analyzed, and the selected Unicode space characters are inserted into inter-sentence, inter-word, end-of-line and inter-paragraph spacings to encode external information while improving embedding efficiency and imperceptivity of the embedded information. UniSpaCh is also reversible where the embedded information can be removed to completely reconstruct the original Microsoft Word document. Experiments were carried out to verify the performance of UniSpaCh as well as comparing it to the existing space-manipulating data hiding methods. Results suggest that UniSpaCh offers higher embedding efficiency while exhibiting higher imperceptivity of white space manipulation when compared to the existing methods considered. In the best case scenario, UniSpaCh produces output document of size almost 9 times smaller than that of the existing method.

Original languageEnglish
Pages (from-to)1075-1082
Number of pages8
JournalJournal of Systems and Software
Issue number5
Publication statusPublished - May 2012
Externally publishedYes


  • DASH
  • Data hiding
  • Space manipulation
  • Unicode character
  • UniSpaCh

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