Universal Stego Post-processing for Enhancing Image Steganography
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It is well known that the modern steganography methods are designed under the framework of distortion minimization, and thus the design of embedding cost is a key issue. Instead of designing embedding cost in existing works, we propose a novel framework to enhance the steganography security via stego post-processing. To ensure the correct extraction of hidden message, we firstly analyze the characteristics of STCs (Syndrome-Trellis Codes) that are widely used in current steganography methods, and then design the rule for post-modification. Furthermore, since the steganography artifacts are typically reflected on image residuals, the proposed post-processing aims to reduce the residual distance between cover and the resulting stego. To this end, we model the proposed stego post-processing as a non-linear integer programming, and implement it via heuristic search. In addition, we carefully determine several important settings in our algorithm, such as the candidate embedding units to be dealt with, the direction and amplitude of post-modification, the adaptive filters for getting residuals, and the distance measure of residuals. Extensive experimental results evaluated on both hand-crafted steganalytic features and deep learning based ones demonstrate that the proposed method can enhance the security performance of various steganography methods effectively and efficiently. In addition, the proposed framework is universal because it can be applied to steganography both in spatial and JPEG domains.
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