Capacity of Steganographic Channels

TL;DR

This paper introduces a formal definition and a general formula for the capacity of steganographic channels, enabling analysis of diverse and complex hiding and detection scenarios using an information-spectrum approach.

Contribution

It presents the first comprehensive, mathematically rigorous framework for calculating steganographic capacity applicable to arbitrary, non-stationary channels.

Findings

Derived a general capacity formula for steganographic channels

Applied the formula to analyze specific hiding and detection methods

Provided insights into the limits of undetectable data hiding

Abstract

This work investigates a central problem in steganography, that is: How much data can safely be hidden without being detected? To answer this question, a formal definition of steganographic capacity is presented. Once this has been defined, a general formula for the capacity is developed. The formula is applicable to a very broad spectrum of channels due to the use of an information-spectrum approach. This approach allows for the analysis of arbitrary steganalyzers as well as non-stationary, non-ergodic encoder and attack channels. After the general formula is presented, various simplifications are applied to gain insight into example hiding and detection methodologies. Finally, the context and applications of the work are summarized in a general discussion.