PHISS: Progressive and hierarchical image segmentation-sharing scheme

Abstract

As a classical secret sharing technique, (k,n) threshold secret image sharing mainly contains the shadow generation phase and the image reconstruction phase. The sensitive secret image is encrypted into n shadows by the dealer in the shadow generation phase, and the secret image can be reconstructed completely by the participants when the number of shadows meet or exceed the threshold k. Previous progressive or hierarchical secret image sharing schemes have some disadvantages (e.g., inflexibility and inefficiency). To solve this problem, we propose a progressive and hierarchical image segmentation-sharing scheme (referred to as PHISS) in this paper. First, the important content region of the sensitive image (called by the target sub-image) is generated by using the proposed image segmentation algorithm. Here the target sub-image refers to the part with the largest amount of information, for instance, the human face in private photo, the pathological region in medical image and the aircraft in military image. Then, in the shadow generation phase, the target sub-image is encrypted into several shadows with hierarchy, and the hierarchies of the generated shadows in the background sub-image are equal. Last, in the reconstruction phase, the background sub-image can be reconstructed completely. The target sub-image has different quality with different number of shadows and different level of shadows. The image can be reconstructed losslessly if and only if all shadows involved. The experimental results and the comparison with similar works demonstrate the feasibility and the superiority of the proposed method.