Locating secret messages in images

  • Authors:
  • Ian Davidson;Goutam Paul

  • Affiliations:
  • SUNY Albany, Albany, NY;SUNY Albany, Albany, NY

  • Venue:
  • Proceedings of the tenth ACM SIGKDD international conference on Knowledge discovery and data mining
  • Year:
  • 2004

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Abstract

Steganography involves hiding messages in innocuous media such as images, while steganalysis is the field of detecting these secret messages. The ultimate goal of steganalysis is two-fold: making a binary classification of a file as stego-bearing or innocent, and secondly, locating the hidden message with an aim to extracting, sterilizing or manipulating it. Almost all steganalysis approaches (known as attacks) focus on the first of these two issues. In this paper, we explore the difficult related problem: given that we know an image file contains steganography, locate which pixels contain the message. We treat the hidden message location problem as outlier detection using probability/energy measures of images motivated by the image restoration community. Pixels contributing the most to the energy calculations of an image are deemed outliers. Typically, of the top third of one percent of most energized pixels (outliers), we find that 87% are stego-bearing in color images and 61% in grayscale images. In all image types only 1% of all pixels are stego-bearing indicating our techniques provides a substantial lift over random guessing.