Reversible Data Hiding With Optimal Value Transfer

Abstract

This paper aims to enhance embedding payload in encrypted images. Here propose a separable reversible data hiding method for encrypted images using Slepian-Wolf source encoding. A novel scheme of reversible data hiding (RDH) in encrypted images using distributed source coding (DSC). After the original image is encrypted by the content owner using a stream cipher, the data-hider compresses a series of selected bits taken from the encrypted image to make room for the secret data. The selected bit series is Slepian-Wolf encoded using low density parity check (LDPC) codes. On the receiver side, the secret bits can be extracted if the image receiver has the embedding key only. In case the receiver has the encryption key only, he/she can recover the original image approximately with high quality using an image estimation algorithm. If the receiver has both the embedding and encryption keys, he/she can extract the secret data and perfectly recover the original image using the distributed source decoding. The hidden data can be completely extracted using the embedding key, and the original image can be approximately reconstructed with high quality using the encryption key. With both keys available, the hidden data can be completely extracted, and the original image perfectly recovered with the aid of some estimated side information. The proposed method achieves a high embedding payload and good image reconstruction quality, and avoids the operations of room-reserving by the sender.

Existing System

RDH techniques of embedding secret message in encrypted images are reviewed. RDH for encrypted image are usually designed for the applications in which the data-hider and the image owner are not the same party. The data-hider cannot access the image content, and the secret message is held by the data-hider. Thus encryption is done by the sender, hiding by the data-hider, and data extraction and/or image reconstruction by the receiver. RDH method for encrypted images by shifting the encrypted histogram of predicted errors, and achieves excellent performance in three aspects: complete reversibility, higher PSNR under given embedding rate, separability between data extraction and image decryption.

Proposed System

The proposed system which consists three phases: image encryption, data embedding, and data extraction/image recovery. In phase I, the sender encrypts the original image into an encrypted image using a stream cipher and an encryption key. In phase II, the data-hider selects and compresses some MSB of the secret image using LDPC codes to generate a spare space, and embeds additional bits into the encrypted image using an embedding key. In phase III, the receiver extracts the secret bits using the embedding key. If he/she has the encryption key, the original image can be approximately reconstructed via image decryption and estimation. When both the encryption and embedding keys are available, the receiver can extract the compressed bits, and implement the distributed source decoding using the estimated image as side information to perfectly recover the original image.

Architecture