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Proceedings Paper

Steganalysis of block-structured stegotext
Author(s): Ying Wang; Pierre Moulin
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Paper Abstract

We study a detection-theoretic approach to steganalysis. The relative entropy between covertext and stegotext determines the steganalyzer's difficulty in discriminating them, which in turn defines the detectability of the stegosystem. We consider the case of Gaussian random covertexts and mean-squared embedding constraint. We derive a lower bound on the relative entropy between covertext and stegotext for block-based embedding functions. This lower bound can be approached arbitrarily closely using a spread-spectrum method and secret keys with large entropy. The lower bound can also be attained using a stochastic quantization index modulation (QIM) encoder, without need for secret keys. In general, perfect undetectability can be achieved for blockwise memoryless Gaussian covertexts. For general Gaussian covertexts with memory, the relative entropy increases approximately linearly with the number of blocks observed by the steganalyzer. The error probabilities of the best steganalysis methods decrease exponentially with the number of blocks.

Paper Details

Date Published: 22 June 2004
PDF: 12 pages
Proc. SPIE 5306, Security, Steganography, and Watermarking of Multimedia Contents VI, (22 June 2004); doi: 10.1117/12.527745
Show Author Affiliations
Ying Wang, Univ. of Illinois/Urbana-Champaign (United States)
Pierre Moulin, Univ. of Illinois/Urbana-Champaign (United States)

Published in SPIE Proceedings Vol. 5306:
Security, Steganography, and Watermarking of Multimedia Contents VI
Edward J. Delp III; Ping W. Wong, Editor(s)

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