Reversible Data Hiding over Encrypted Images via Intrinsic Correlation in Block-Based Secret Sharing

Reversible data hiding over encrypted images (RDH-EI) is an important technique for secure cloud image management but existing schemes often exhibit high computational complexity, low embedding rates, and excessive data expansion. This article addresses these issues by analyzing block-based secret sharing, revealing significant intra-block data redundancy. Based on this observation, we propose two space-preserving methods: the direct space-vacating method and the image-shrinking-based space-vacating method. Using these techniques, we design two novel RDH-EI schemes: a high-capacity RDH-EI scheme and a size-reduced RDH-EI scheme. The high-capacity RDH-EI scheme directly creates embedding space in encrypted images, eliminating the need for complex space-vacating operations and achieving higher and more stable embedding rates. In contrast, the size-reduced RDH-EI scheme minimizes data expansion by discarding unnecessary shares, resulting in smaller encrypted images. Experimental results show that the high-capacity RDH-EI scheme outperforms existing methods in terms of embedding capacity, while the size-reduced RDH-EI scheme achieves strong performance in minimizing data expansion. Both schemes offer effective solutions for RDH-EI challenges.