A Robust Hybrid DWT-DCT and Up- sampling Approach for Multiple Image Hiding

The task of multi-image hiding involves embedding several confidential images within a single cover image such that the camouflage-image remains visually indistinguishable from the original, and all confidential images can be perfectly reconstructed. In this paper, we propose a novel hybrid image steganography method that combines DWT- DCT-based preprocessing and a high-ratio up-sampling mechanism with a spatial-domain reversible embedding scheme. First, a dummy embedding is performed using the Discrete Wavelet Transform (DWT) and Discrete Cosine Transform (DCT) on the interpolated pixels of an 8x up- sampled cover image. This step acts as a visual smoothing mechanism to improve the fidelity of the embedding surface while maintaining PSNR ≈ ∞. Then, the actual embedding of multiple confidential images is performed using a block- based reversible data steganography method with Euclidean distance-guided block matching and pixel-level transformation. This combined approach ensures high steganography capacity, strong robustness, and perfect reconstruction of all confidential images. Experimental results demonstrate that the proposed method outperforms traditional image steganography schemes in terms of visual quality, imperceptibility, and reversibility, making it suitable for secure multimedia communication and sensitive data storage.