Title: Reversible data hiding in encrypted image via block classification and adaptive coding

Authors: Yuanyuan Fu; Shiliang He; Jiaohua Qin

Addresses: College of Information and Electronics Engineering, Hunan City University, Yiyang, 413000, China; School of Electronic Information and Physics, Central South University of Forestry and Technology, Changsha, 410004, China ' School of Electronic Information and Physics, Central South University of Forestry and Technology, Changsha, 410004, China ' School of Electronic Information and Physics, Central South University of Forestry and Technology, Changsha, 410004, China

Abstract: Reversible data hiding in encrypted images (RDHEI) enables secret information embedding while ensuring error-free data extraction and perfect image recovery. However, the fixed vacating room method used to divide encrypted images into blocks results in limited embedding space. To address this limitation, this paper proposes a block classification and adaptive coding-based RDHEI scheme. Specifically, block-level encryption and permutation are first applied to the original image. Then, adaptive block classification is conducted, and block labels are recorded in a block label location map to achieve first-stage room vacating. For blocks with insufficient available space, adaptive coding and block label map compression are further employed to realise second-stage room vacating. Experimental results demonstrate that the proposed method achieves reversibility and separability while providing a higher embedding rate than existing approaches.

Keywords: reversible data hiding; encrypted images; block classification; adaptive coding; vacating room; embedding capacity; block-level encryption.

DOI: 10.1504/IJAACS.2026.154849

International Journal of Autonomous and Adaptive Communications Systems, 2026 Vol.19 No.3, pp.321 - 337

Received: 22 Aug 2025
Accepted: 31 Oct 2025

Published online: 16 Jul 2026 *

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