Atallah

CERIAS TR 2002-54

conference

Two main results in the area of information hiding in natural lan- guage text are presented. A semantically-based scheme dramatically im- proves the information-hiding capacity of any text through two tech- niques: (i) modifying the granularity of meaning of individual sentences, whereas our own previous scheme kept the granularity fixed, and (ii) halv- ing the number of sentences affected by the watermark. No longer a “long text, short watermark” approach, it now makes it possible to watermark short texts like wire agency reports. Using both the above-mentioned se- mantic marking scheme and our previous syntactically-based method hides information in a way that reveals any non-trivial tampering with the text (while re-formatting is not considered to be tampering—the problem would be solved trivially otherwise by hiding a hash of the text) with a probabil- ity 1–2–b(n+1), n being its number of sentences and b a small positive integer based on the extent of co-referencing.

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2002

Atallah

CERIAS

2002-01-01