Improving Steganographic Security by Synchronizing the Selection Channel
Tomáš Denemark, Jessica Fridrich · 2015
This paper describes a general method for increasing the security of additive steganographic schemes for digital images represented in the spatial domain. Additive embedding schemes first assign costs to individual pixels and then embed the desired payload by minimizing the sum of costs of all changed pixels. The proposed framework can be applied to any such scheme -- it starts with the cost assignment and forms a non-additive distortion function that forces adjacent embedding changes to synchronize. Since the distortion function is purposely designed as a sum of locally supported potentials, one can use the Gibbs construction to realize the embedding in practice. The beneficial impact of synchronizing the embedding changes is linked to the fact that modern steganalysis detectors use higher-order statistics of noise residuals obtained by filters with sign-changing kernels and to the fundamental difficulty of accurately estimating the selection channel of a non-additive embedding scheme implemented with several Gibbs sweeps. Both decrease the accuracy of detectors built using rich media models, including their selection-channel-aware versions.