Reversible Data Hiding in Encrypted Images Based on Bit‐Plane Classification and Adaptive Group Coding

ABSTRACT Reversible data hiding in encrypted images (RDH‐EI) is a key technique for secure communication, secure cloud storage and privacy protection. Most existing RDH‐EI algorithms rely on a single and static bit‐plane encoding strategy, failing to fully exploit the structural differences of bit‐planes from the block level to the sequence level, thereby limiting further improvements on embedding capacity. To address this issue, this paper proposes a novel RDH‐EI algorithm based on Bit‐plane Classification and Adaptive Group Coding (hereafter BCAGC algorithm). The core contributions are as follows: (1) A bit‐plane classification mechanism is proposed. It categorises bit‐planes into simple or complex types according to the number of non‐all‐zero 4‐bit sequence (NAZ‐4BS) patterns. (2) An adaptive group coding scheme is proposed. It dynamically selects between fixed‐length coding and Huffman coding based on bit‐plane types and the frequency distribution of NAZ‐4BS patterns, thereby achieving compact coding tables and efficient bit‐plane compression. Experimental results demonstrate that the proposed BCAGC algorithm achieves average embedding rates of 4.1472, 4.0565 and 3.4465 bpp on the BOSSbase, BOWS‐2 and UCID datasets, respectively, outperforming several state‐of‐the‐art RDH‐EI methods.