Discriminability-Aware Intermediate Domains for Mismatched Steganalysis

This letter proposes GDNet equipped with the generation of discriminative mixing regions (GDMR) and discriminability-aware local image mixing (DLIM), a steganalysis network aiming at alleviating significant accuracy degradation caused by cover-source mismatch (CSM), which pertains to the situation where source and target domains come from different distributions. GDNet guides a steganalyzer trained on the source domain to the target domain by mixing the source and target images at the region-level and pixel-level to construct a discriminative intermediate domain. On the one hand, GDMR designs an epoch-related region-level mixing ratio to control the size of the mixed region, and based on this ratio, selects the regions within the target image strongly related to the stego signal to participate in the generation of the intermediate domain, while suppressing other regions weakly related to the stego signal. On the other hand, DLIM utilizes the pixel-level mixing ratio to reduce the impact of the regions weakly related to the stego signal on the discriminability of the intermediate domain as the region-level mixing ratio increases, thereby increasing the diversity of the intermediate domain. Experimental results demonstrate that GDNet significantly outperforms existing methods across various CSM scenarios.