Reversible Data Hiding Over Encrypted Images via Preprocessing-Free Matrix Secret Sharing.

Cloud service is a natural choice to store and manage the exponentially produced images. Data privacy is one of the most concerned points in cloud-based image services. Reversible data hiding over encrypted images (RDH-EI) is an effective technique to securely store and manage confidential images in the cloud. However, existing RDH-EI schemes have obvious weaknesses such as reliable key management system dependence and single point of failure. To securely store and manage confidential images in the cloud, in this study, we propose a new reversible data hiding strategy via image secret sharing. We first design a secure ( r,n )-threshold preprocessing-free matrix secret sharing (PFMSS) technique. It can directly share m -bit data by matrix multiplication without preprocessing. Using the PFMSS, we further design a secure ( r,n )-threshold reversible data hiding scheme over encrypted images. The content owner divides a confidential image into n shares without accessing to a secret encryption key, and then sends the n shares to n cloud-based image servers from competing providers. For each share, some additional data, e.g., integrity and identification of the image, can be embedded into it and these data can also be losslessly extracted. An authorized receiver can recover the confidential image from r shares. By designing, the content owner doesn’t need to access a secret key when encrypting the image and the scheme can withstand n - r points of failure. Simulation results show that our scheme can ensure image content confidentiality and has a much larger embedding capacity compared to state-of-the-art schemes.