Reversible data hiding in encrypted images using Pixel Shifting Approach (PSA)

This study proposes a novel technique for reversibly embedding data within encrypted images, specifically utilizing a Pixel Shifting Approach (PSA). Traditional data hiding methods commonly employ the modification of the least significant bits (LSBs) of pixels in the original image. In contrast, methods using encrypted cover images offer a wider range of data hiding techniques that are not constrained by LSB modifications. The proposed data hiding method embeds data into an encrypted cover image by dividing it into non-overlapping blocks and then permuting pixels within each block according to a defined rule, rather than modifying the LSBs of pixels. The entropy of the image remains preserved after data embedding, making it difficult to detect the location of hidden data. To extract the hidden data, the encrypted image is decrypted, and the smoothness of each block is measured. The block with the lowest smoothness is identified as the one containing the hidden data, which is also the original block. This is because the pixels within each block have different statistical properties compared to other blocks, allowing for data recovery. The proposed method offers the advantage of embedding 4 bits of data per block, surpassing the performance of the existing Modified Pixel Shifting Approach (MPSA). Moreover, the entropy preservation of the stego-image is comparable to MPSA, while the algorithm's execution time is more efficient. The simpler data hiding rule compared to MPSA enables faster encoding and decoding. Reversibility is guaranteed by preserving the correlation among pixels within each block when extracting data from the stego-image and restoring the original image. Experimental results demonstrate that the proposed method significantly outperforms existing techniques in terms of data hiding efficiency and security.