Secure Sudoku Mapping for Dual-Image Reversible Data Hiding

Abstract

Reversible data hiding in encrypted images (RDHEI) often creates embedding room by preserving or preprocessing image redundancy, thereby coupling the hiding layer to a specialized encryption model. This paper presents a dual-image method that works directly on AES-CTR ciphertext. Its design rests on four elements: a keyed Sudoku coordinate code for carrying two base-8 digits per accepted pair; exact reconstruction of each ciphertext pair from inter-block displacement; AES-GCM framing for payload confidentiality and integrity; and an adaptive movement threshold that selects the lowest-distortion mappings able to accommodate the complete frame. The data hider requires neither plaintext nor the image-encryption key, and no location map is transmitted. On sixteen 512×512 grayscale images, the method achieves a mean maximum net rate of 1.4187 bits per transmitted pixel. At ERt=1.0, the two marked outputs reach mean PSNR values of 47.65 dB, and all 160 image-rate trials yield zero payload error and pixel-exact recovery. An independent implementation of the embedding and recovery layer of Venkatesh et al. is also examined; published and reproduced results are reported separately where the original specification leaves ambiguity. The experiments show that the proposed architecture provides predictable payload, low carrier-domain distortion, authenticated framing, and exact recovery while retaining standard image encryption.