Toward Secure and Robust Steganography for Black-Box Generated Images

The progression of text-to-image generation models has incited an upsurge in disseminating generated images across social networks, providing a fertile ground for steganography. Presently, the majority of generated images are crafted utilizing black-box APIs and social networks employ lossy compression on uploaded images. However, there is a dearth of steganographic research conducted on black-box generated images, and the distinctive attributes of the generation model have not been harnessed, resulting in a performance that fails to achieve both security and robustness simultaneously. To address these challenges, we propose an innovative steganographic framework, Steganography based on Concomitantly shaRing generated Images and PrompTs (SCRIPT). This framework ensures security and robustness by precisely identifying robust coefficients within the image for message embedding and synchronizing their positions. For precise identification, we assess the ability of coefficients to withstand unknown spatial perturbations, employing this metric to quantify their robustness. For positional synchronization of robust coefficients, the relevant prompts are uploaded alongside the stego image, allowing the recipient to reconstruct the cover image using a mutually agreed random seed and the provided prompt. Subsequently, positional synchronization is achieved by consistently adopting an identical method for selecting robust coefficients between the sender and the recipient. By amalgamating these strategies, SCRIPT significantly surpasses prior algorithms. Empirical results validate our approach, with a noteworthy 98% message extraction success rate and a substantial 20%+ enhancement in security across diverse payloads.