Unbalanced JPEG image steganalysis via multiview data match

• This work focuses on the problem of unbalance JPEG images steganalysis.
• A semi-supervised learning algorithm which integrates weighted Fisher linear discriminant and K-means clustering (WFLDK) into a join framework is devised to solve unbalanced image steganalysis.
• Multiview match resampling method is proposed to rebalance the unbalanced training images.

Image steganalysis must address the matter of learning from unbalanced training sets where the cover objects (normal images) always greatly outnumber the stego ones. But the research in unbalanced image steganalysis is seldom seen. This work just focuses on the problem of unbalance JPEG images steganalysis. In this paper, we propose a frame of feature dimension reduction based semi-supervised learning for high-dimensional unbalanced JPEG image steganalysis. Our method uses standard steganalysis features, and selects the confident stego images from the unlabeled examples by multiview match resampling method to rebalance the unbalanced training images. Furthermore, weighted Fisher linear discriminant (WFLD) is proposed to find the proper feature subspace where K-means provides the weight factor for WFLD in return. Finally, WFLD and K-means both work in an iterative fashion until convergence. Experimental results on the MBs and nsF5 steganographic methods show the usefulness of the developed scheme over current popular feature spaces.