A SCALABLE REVERSIBLE DATA HIDING SCHEME IN ENCRYPTED IMAGES USING PIXEL-GROUP SECRET SHARING

Reversible Data Hiding in Encrypted Images (RDHEI) enables the embedding of auxiliary information into encrypted images while guaranteeing perfect recovery of both the original image and the embedded data. Existing secret-sharing-based RDHEI schemes supporting multiple data-hiders suffer from a fundamental limitation: the total embedding capacity is fixed, leading to a rapid reduction in embedding rate as the number of shared images increases. This severely restricts their scalability in multi-user environments. In this paper, a novel RDHEI framework based on pixel-group polynomial secret sharing over the Galois Field GF (2⁸) is proposed. By encoding multiple pixels as coefficients of a polynomial and redistributing the resulting shared pixel into multiple carrier pixels, significant reversible vacant embedding space is generated. This space is exploited to embed secret data without affecting polynomial reconstruction. Consequently, the proposed scheme supports multiple independent data-hiders while maintaining a fixed embedding rate per shared image. Extensive experimental results demonstrate that the proposed method achieves higher embedding capacity, perfect reversibility, and superior scalability compared with existing state-of-the-art RDHEI schemes.