Reversible data hiding in encrypted images by Reserving room before encryption

REVERSIBLE DATA HIDING IN ENCRYPTED IMAGES BY

RESERVING ROOM BEFORE ENCRYPTION

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ABSTRACT

Recently, more and more attention is paid to reversible data hiding (RDH) in encrypted images, since it maintains the excellent property that the original cover can be losslessly recovered after embedded data is extracted while protecting the image content’s confidentiality. All previous methods embed data by reversibly vacating room from the encrypted images, which may be subject to some errors on data extraction and/or image restoration. In this paper, we propose a novel method by reserving room before encryption with a traditional RDH algorithm, and thus it is easy for the data hider to reversibly embed data in the encrypted image. The proposed method can achieve real reversibility, that is, data extraction and image recovery are free of any error. Experiments show that this novel method can embed more than 10 times as large payloads for the same image quality as the previous methods, such as for PSNR =40dB.

EXISTING SYSTEM:

In this framework, a content owner encrypts the original image using a standard cipher with an encryption key. After producing the encrypted image, the content owner hands over it to a data hider (e.g., a database manager) and the data hider can embed some auxiliary data into the encrypted image by losslessly vacating some room according to a data hiding key. Then a receiver, maybe the content owner himself or an authorized third party can extract the embedded data with the data hiding key and further recover the original image from the encrypted version according to the encryption key. In all methods of [16]–[18], the encrypted 8-bit gray-scale images are generated by encrypting every bit-planes with a stream cipher. The method in [16] segments the encrypted image into a number of nonoverlapping blocks sized by a*a ; each block is used to carry one additional bit. To do this, pixels in each block are pseudo-randomly divided into two sets S1and S2 according to a data hiding key. If the additional bit to be embedded is 0, flip the 3 LSBs of each encrypted pixel in S1, otherwise flip the 3 encrypted LSBs of pixels in S2. For data extraction and image recovery, the receiver flips all the three LSBs of pixels in to form a new decrypted block, and flips all the three LSBs of pixels in to form another new block; one of them will be decrypted to the original block. Due to spatial correlation in natural images, original block is presumed to be much smoother than interfered block and embedded bit can be extracted correspondingly. However, there is a risk of defeat of bit extraction and image recovery when divided block is relatively small (e.g.,a=8 ) or has much fine-detailed textures. Hong et al. [17] reduced the error rate of Zhang’smethod [16] by fully exploiting the pixels in calculating the smoothness of each block and using side match. The extraction and recovery of blocks are performed according to the descending order of the absolute smoothness difference between two candidate blocks and recovered blocks can further be used to evaluate the smoothness of unrecovered blocks, which is referred to as side match. Zhang’s method in [18] pseudo-randomly permuted and divided encrypted image into a number of groups with size of L. The P LSB-planes of each group are compressed with a parity-check matrix and the vacated room is used to embed data. For instance, denote the pixels of one group by x1..xL, and its encrypted LSB-planes by that consists of P.L bits.

DISADVANTAGES OF EXISTING SYSTEM:

·        All previous methods embed data by reversibly vacating room from the encrypted images, which may be subject to some errors on data extraction and/or image restoration.

·        It is difficult for data hider to reversibly hide the data behind the image.

PROPOSED SYSTEM:

Since losslessly vacating room from the encrypted images is relatively difficult and sometimes inefficient, why are we still so obsessed to find novel RDH techniques working directly for encrypted images? If we reverse the order of encryption and vacating room, i.e., reserving room prior to image encryption at content owner side, the RDH tasks in encrypted images would be more natural and much easier which leads us to the novel framework, “reserving room before encryption (RRBE)”. As shown in Fig. 1(b), the content owner first reserves enough space on original image and then converts the image into its encrypted version with the encryption key. Now, the data embed ding process in encrypted images is inherently reversible for the data hider only needs to accommodate data into the spare space previous emptied out. The data extraction and image recovery are identical to that of Framework VRAE. Obviously, standard RDH algorithms are the ideal operator for reserving room before encryption and can be easily applied to Framework RRBE to achieve better performance compared with techniques from Framework VRAE. This is because in this new framework, we follow the customary idea that first losslessly compresses the redundant image content (e.g., using excellent RDH techniques) and then encrypts it with respect to protecting privacy. Next, we elaborate a practical method based on the Framework “RRBE”, which primarily consists of four stages: generation of encrypted image, data hiding in encrypted image, data extraction and image recovery.Note that the reserving operation we adopt in the proposed method is a traditional RDH approach.

ADVANTAGES OF PROPOSED SYSTEM:

·        In this system it uses traditiosnal RDH algorithm, and thus it is easy for the data hider to reversibly embed data in the encrypted image.

·        Using this system data extraction and image recovery are free of any error.

SYSTEM ARCHITECHTURE:

SYSTEM CONFIGURATION:-

HARDWARE REQUIREMENTS:-

ü  Processor                     -Pentium –III

ü  Speed                          -    1.1 Ghz

ü  RAM                           -    256 MB(min)

ü  Hard Disk                   -   20 GB

ü  Floppy Drive   -    1.44 MB

ü  Key Board                  -    Standard Windows Keyboard

ü  Mouse             -    Two or Three Button Mouse

ü  Monitor                       -    SVGA

SOFTWARE REQUIREMENTS:-

v   Operating System                   : ANDROID  

v   Front End                                : Java

v   Database                                 : SQLite

v   Tool                                         : Eclipse

REFERENCE:

Kede Ma, Weiming Zhang, Xianfeng Zhao, Nenghai Yu, and Fenghua Li, “REVERSIBLE DATA HIDING IN ENCRYPTED IMAGES BY RESERVING ROOM BEFORE ENCRYPTION” IEEE TRANSACTIONS ON INFORMATION FORENSICS AND SECURITY, VOL. 8, NO. 3, MARCH 2013.