## Cryptology ePrint Archive: Report 2000/028

An Information-Theoretic Model for Steganography

Christian Cachin

Abstract: An information-theoretic model for steganography with a passive adversary is proposed. The adversary's task of distinguishing between an innocent cover message $C$ and a modified message $S$ containing hidden information is interpreted as a hypothesis testing problem. The security of a steganographic system is quantified in terms of the relative entropy (or discrimination) between the distributions of $C$ and $S$, which yields bounds on the detection capability of any adversary. It is shown that secure steganographic schemes exist in this model provided the covertext distribution satisfies certain conditions. A universal stegosystem is presented in this model that needs no knowledge of the covertext distribution, except that it is generated from independently repeated experiments.

Category / Keywords: foundations / information hiding, covert channels, steganography

Publication Info: To appear in Information and Computation.

Date: received 11 Jun 2000, last revised 4 Mar 2004

Contact author: cachin at acm org

Available format(s): Postscript (PS) | Compressed Postscript (PS.GZ) | PDF | BibTeX Citation

Note: This is an extensively revised version of the paper presented at Information Hiding Workshop '98.

Short URL: ia.cr/2000/028

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