# Edge-Guided Dual-Stream U-Net for Secure Image Steganography
## 4 Experiments
### Visualisation and Analysis of Results  
Image-hiding technology must ensure imperceptibility in a subjective sense. During subjective visual evaluations, we observed that the generated stego images are nearly indistinguishable from the cover images when viewed with the naked eye. To further verify the security of the stego images, we conducted residual analysis, which calculates the difference between the stego and cover images to produce a residual map that visually highlights their differences. Four image sets were randomly selected for this analysis, and residual maps were generated for both the cover and stego images. As illustrated in Figure 5, under a Residual \(\times\)1 scale, the residual maps are almost entirely black, indicating that the hidden information is imperceptible and the differences between the images are negligible. When scaled to Residual \(\times\)10, only faint contours are visible, with no secret information revealed. These findings demonstrate the high security and imperceptibility of our method, as the embedding process minimally alters the original cover image, enabling the secure concealment and transmission of information.  
\begin{table}
\begin{tabular}{c c c c} \hline  & **ECA** & **CBAM** & **MSMA** \\ \hline PSNR & 35.73 & 35.22 & 37.41 \\ SSIM & 0.91 & 0.89 & 0.93 \\ ERROR & 0.00 & 0.00 & 0.00 \\ \hline \end{tabular}
\end{table}
Table 10: Ablation experiments results of MSMA attention mechanism on the Div2k dataset.  
\begin{table}
\begin{tabular}{c c c c c c} \hline
**EDSU** & **MSMA** & **InceptionDWK** & **PSNR** & **SSIM** & **Error Rate** \\ \hline \(\times\) & \(\times\) & \(\times\) & 32.51 & 0.89 & \(7\times 10^{-5}\) \\ \(\surd\) & \(\times\) & \(\times\) & 35.04 & 0.92 & 0.00 \\ \(\surd\) & \(\times\) & \(\surd\) & 36.29 & 0.87 & 0.00 \\ \(\surd\) & \(\surd\) & \(\times\) & 37.41 & 0.93 & 0.00 \\ \(\surd\) & \(\surd\) & \(\surd\) & 38.92 & 0.95 & 0.00 \\ \hline \end{tabular} Note: \(\surd\) indicates the module is used, and \(\times\) indicates the module is removed.  
\end{table}
Table 9: Ablation experiments results on the Div2k dataset.  
In addition to residual analysis, we also evaluated the statistical consistency between the stego and cover images using pixel histograms, a tool that visualizes pixel value distributions by dividing the range into intervals and counting pixel frequencies within each. As shown in Figure 6, the first and third columns display the Cover images, while the second and fourth columns show the Stego images. The histograms reveal the distributions of the red, green, and blue channels (R, G, and B values), represented by red, green, and blue lines, respectively. The results indicate minimal differences in pixel value distribution between the Cover and Stego images. Notably, closer examination reveals that the pixel value distributions of the cover images become smoother after embedding the steganographic information. This observation suggests that our method not only effectively embeds secret information but also enhances the statistical properties of the stego images, making their distribution more similar to that of natural images. This improvement bolsters the resistance of stego images to detection, further enhancing the concealment and security of the method.  
Figure 5: Visualization of cover, steganography, and corresponding residual images.