Novelty detection in blind steganalysis

  • Authors:
  • Tomáš Pevný;Jessica Fridrich

  • Affiliations:
  • INPG - Gipsa-Lab, Grenoble cedex, France;Binghamton University, Binghamton, NY, USA

  • Venue:
  • Proceedings of the 10th ACM workshop on Multimedia and security
  • Year:
  • 2008

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Abstract

It is generally believed that a blind steganalyzer trained on sufficiently many diverse steganographic algorithms will become universal in the sense that it will generalize to previously unseen (novel) stego methods. While this is a partially correct statement if the embedding mechanism of the novel method resembles some of the methods on which the classifier was trained, we demonstrate that if the classifier is presented with stego images produced by a completely different embedding mechanism, it may fail to detect the images as stego even for an otherwise fairly easily detectable method. Motivated by this observation, we explore two approaches for construction of universal steganalyzers - one-class and one-against-all classifiers. Their advantages and disadvantages are discussed and performance compared on a wide variety of steganographic algorithms. One-against-all classifiers have generally better performance than approaches based on characterizing just the class of covers but they may fail catastrophically on previously unseen stego algorithms. One-class methods are less likely to fail to detect unknown stego algorithms but have lower overall detection accuracy on known stego methods. The suitability of each approach thus depends on the application.