Training-Free Coverless Multi-Image Steganography with Access Control
This addresses the lack of access control in coverless steganography for scalable and privacy-sensitive information hiding, representing an incremental improvement.
The paper tackled the problem of enabling robust access control in coverless image steganography for multi-user settings, and the result was MIDAS, a training-free diffusion-based framework that outperformed existing baselines in access control, image quality, diversity, robustness, and steganalysis resistance.
Coverless Image Steganography (CIS) hides information without explicitly modifying a cover image, providing strong imperceptibility and inherent robustness to steganalysis. However, existing CIS methods largely lack robust access control, making it difficult to selectively reveal different hidden contents to different authorized users. Such access control is critical for scalable and privacy-sensitive information hiding in multi-user settings. We propose MIDAS, a training-free diffusion-based CIS framework that enables multi-image hiding with user-specific access control via latent-level fusion. MIDAS introduces a Random Basis mechanism to suppress residual structural information and a Latent Vector Fusion module that reshapes aggregated latents to align with the diffusion process. Experimental results demonstrate that MIDAS consistently outperforms existing training-free CIS baselines in access control functionality, stego image quality and diversity, robustness to noise, and resistance to steganalysis, establishing a practical and scalable approach to access-controlled coverless steganography.