An information-theoretic model for steganography

  • Authors:
  • Christian Cachin

  • Affiliations:
  • IBM Zurich Research Laboratory, Säumerstr. 4, CH-8803 Rüschlikon, Switzerland

  • Venue:
  • Information and Computation
  • Year:
  • 2004

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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.