REVERSIBLE DATA HIDING IN ENCRYPTED IMAGES BY RESERVING ROOM BEFORE ENCRYPTION TECHNIQUE AND LSB MATCHING ALGORITHM

International Journal of Technical Research and Applications e-ISSN: 2320-8163,
www.ijtra.com Volume 3, Issue 3 (May-June 2015), PP. 52-54
52 | P a g e
REVERSIBLE DATA HIDING IN ENCRYPTED
IMAGES BY RESERVING ROOM BEFORE
ENCRYPTION TECHNIQUE AND LSB
MATCHING ALGORITHM
Harshali Sanglikar1, Neha Jadhav2, Pawankumar Thorat3, Rubeena Khan4
Department of Computer engineering
Modern Education Society’s college of engineering
Savitribai Phule Pune University, Pune
harshali101@gmail.com, neha.jadhav@gmail.com, thoratpawankumar@gmail.com
Rubeena.khan@mescoepune.org
Abstract:- In recent years the topic of steganography has become
very popular and a lot of research is being done in this field.
Reversible data hiding is a method in which the image in which
the encrypted data is hidden is losslessly recovered. In this paper
we have proposed such a method that the previous work done
limitations can be overcome. In this paper, we embed the
encrypted data in the image by using LSB matching technique for
reserving room, so that fast, optimal and lossless steganography
is achieved. The proposed method provides total reversibility,
that is, data extraction and image recovery.
Index terms- reversible data hiding, encryption, data hiding and
extraction.
I. INTRODUCTION
The basic concept of steganography is to hide the very
presence of communication by embedding message into
innocuous-looking cover objects.
Reversible data hiding is a method to hide (embed)
additional message into some distortion free unacceptable
cover media. It is needed in the fields such as military or
medical images, with a reversible manner are use so that the
original cover content can be perfectly recovered after
extraction of the hidden message[1].
In[1][3][5], separable reversible data hiding technique a
user or content owner encrypts the original carrier image then
a data hider compress the image to create space to for
accommodation of some additional data. However, in[4] some
circumstances if the user (content owner) does not trust the
service provider then he may encrypt it (secret data) when it is
to be transmitted ted, channel provider without any knowledge
of the cryptographic key may compress the encrypted data due
to the limited channel resource[2].
Data hiding is referred to as a process to hide data or embed
data, i.e, the data embedding process links two sets, a set of
the embedded data and another set of the carrier media or
cover media data. In most cases of data hiding, the cover
media or carrier image becomes distorted due to data hiding
and cannot be inverted back to the original image as it was
before. That is, media has permanent distortion even after the
embedded data have been removed. In some applications, such
as medical diagnosis and law enforcement it is desired that the
original cover media can be recovered efficiently with no
loss.[7][8][9] The marking techniques satisfying this
requirement are referred to as reversible, lossless, distortion
free or invertible data hiding techniques. The separable means
which is able to separate, in other words, we can separate the
some things, activities using suitable criteria is as said.
Separable reversible data hiding concept is the separation of
activities i.e. extraction of original cover image and extraction
of payload. Separable data hiding key is the separation that
exists according to keys. Here at the receiver side, there are
three different cases are encountered ie image recover, data
extraction and data decryption.
There are several methods for data hiding in images
available now, but most of them are not reversible in nature. In
[1] paper method to achieve pure recovery of image and data
is proposed. Thus here gives same importance for both image
and data. In the Existing System, Reserving Room before
Encryption technique is following. As losslessly reserving
room in the encrypted images is relatively difficult and
sometimes inefficient, but still we are so obsessed to find
novel RDH techniques working directly for Encrypted Images.
The method is of compressing the encrypted LSBs to reserve
room for additional data by finding syndromes of a parity
check matrix, and the side information used at the receiver
side is also the spatial correlation of decrypted images. All the
three methods try to vacate room from the encrypted images
directly.
II. PROPOSED SYSTEM
In proposed method can achieve real reversibility, that
is, data extraction and image recovery are free of any error. 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)”. Not
only does the proposed method separate data extraction from
image decryption but also achieves excellent performance in
two different prospects. Real reversibility is realized, that is,
data extraction and image recovery are free of any error. For
given embedding rates, the PSNRs of decrypted image
containing the embedded data are significantly improved; and
for the acceptable PSNR, the range of embedding rates is
greatly enlarged. The proposed method allows us to use any
format of the image in which we want to store data i.e jpeg,
png, bmp etc. The method allows us to use any format of data
file i.e pdf,docx, etc.
A. Encrypted Image Generation
In this module, to construct the encrypted image, the first
stage can be divided into two steps. Image Partition and Self
Reversible Embedding followed by image encryption. At the
beginning, image partition step divides original image into two
parts and then, the LSBs of the least dominant channels in the
image are reversibly embedded into the dominant colour
channel with a standard RDH algorithm so that LSBs of can be

53 | P a g e
used for accommodating messages; at last, encrypt the
rearranged image to generate its final version.
B. Data hiding in encrypted image
In this module, 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
lossless 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.
C. Data extraction and image recovery
In this module, Extracting Data from Encrypted Images to
manage and update personal information of images which are
encrypted for protecting clients’ privacy, an inferior database
manager may only get access to the data hiding key and have
to manipulate data in encrypted domain. When the database
manager gets the data hiding key, he can decrypt and extract
the additional data by directly reading the decrypted version.
When requesting for updating information of encrypted
images, the database manager, then, updates information
through LSB replacement and encrypts up dated information
according to the data hiding key all over again. As the whole
process is entirely operated on encrypted domain, it avoids the
leakage of original content.
D. Data extraction and image restoration
In this module, after generating the marked decrypted
image, the content owner can further extract the data and
recover original image. Reversible hiding allows extraction of
the original host signal and also the embedded message. There
are two important requirements for reversible data hiding
techniques: the embedding capacity should be large; and
distortion should be low. These two requirements conflict with
each other. In general, a higher embedding capacity results in
a higher degree of distortion. An improved technique embeds
the same capacity with lower distortion or vice versa. For the
image restoration we have to follow the specified steps by
which we can easily recover the original image. After the
image encryption the image must be considered as an
individual unit of work so we can fully concentrate on the
watermarking technique and proceed further
III. AES ALGORITHM
The Advanced Encryption Standard (AES) specifies a
FIPS-approved cryptographic algorithm that can be used to
protect electronic data. The AES algorithm is a symmetric
block cipher that can encrypt (encipher) and decrypt
(decipher) information. Encryption converts data to an
unintelligible form called ciphertext; decrypting the ciphertext
converts the data back into its original form, called plaintext.
The AES algorithm is capable of using cryptographic keys of
128, 192, and 256 bits to encrypt and decrypt data in blocks of
128 bits. The AES algorithm is based on permutations and
substitutions. Permutations are rearrangements of data, and
substitutions replace one unit of data with another. AES
performs permutations and substitutions using several
different techniques.
In our system we are using 128 bit key and in AES this is
represented by Nb = 4, which reflects the number of 32-bit
words (number of columns) in the State. The length of the
Cipher Key, K, is 128. The key length is represented by Nk =
4, 6, or 8, which reflects the number of 32-bit words (number
of columns) in the Cipher Key. The number of rounds to be
performed during the execution of the algorithm is dependent
on the key size. The number of rounds is represented by Nr,
where Nr = 10 when
Nk = 4, Nr = 12 when Nk = 6, and Nr = 14 when Nk = 8. For
both its Cipher and Inverse Cipher, the AES
Algorithm uses a round function that is composed of four
different byte-oriented transformations:
1) Substitution using a substitution table (S-box).
2) Shifting rows of the State array by different offsets
3) Mixing the data within each column of the State
Array
4) Adding a Round Key to the State.
IV. LSB MATCHING ALGORITHM
Least Significant Bit Embedding’s (LSB) are a general
stenographic technique that may be employed to embed data
into a variety of digital media, but one of the most studied
applications is using LSB embedding to hide one image inside
another. In our system we are using LSB matching algorithm
for embedding data in the image. For embedding data in the
image we first find the dominant channel in the image. The
dominant channel is basically the colour which is most present
in the image. The other two channels that are present in the
image are used for storing the data in the image. Before
storing the data in the image we reserve room that is we store
the values of the least dominant channels LSB’s in the
dominant channel by EXORing them. The space for storing
the data in the image is now reserved. The data that is to be
stored in the image is first compared with the LSBs of the
image’s least dominant channel, if the values are same then the
bits are kept as it is and if there is a mismatch then the values
are replaced. Thus the algorithm saves a lot of computation
time and also is overcoming the abruptly replacing the LSB
bits of the image.
V. FEATURES OF SYSTEM
A. Three Keys for more Data Security
Encrypted data is hidden in Encrypted Image with separate
keys for Data Encryption, Image Encryption and Data Hiding.
For decrypting of data receiver should have both Data
Encryption and Data hiding key.
B. Protection for auto generated keys
To perform any operation the user has only 3 attempts. If user
is fail to perform any of operation means user enter wrong 3
times then the system is goes to not responding state and one
mail with receiver computer IP address is send to the admin.
C. Allows any type of data or image file
The system can work on any format of data file like .pdf,
.docx, .rtf etc and any format of image file like .jpeg, .bmp,
.png etc.
D. Allows large data files to be encrypted
The system allows very large size of data file to be encrypted
easily as we are storing the image in the image file. If we want
to store large size data in the image we would have to take a
bigger image to store that much amount of data in it.
E. Faster computation time
The use of multithreading allows faster computation both
while image encryption and decryption.

54 | P a g e
AES flow chart
Illustration of image partitioning and embedding process
VI. CONCLUSION
Reversible data hiding in encrypted images is a new topic
drawing attention because of the privacy-preserving
requirements from cloud data management. Previous methods
implement RDH in encrypted images by vacating room after
encryption, as opposed to which we proposed by reserving
room before encryption. Thus the data hider can benefit from
the extra space emptied out in previous stage to make data
hiding process effortless. The proposed method can take
advantage of all traditional RDH techniques for plain images
and achieve excellent performance without loss of perfect
secrecy. Furthermore, by this novel method can achieve
reversibility as well as separate data extraction and greatly
improvement on the quality of marked decrypted images
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REVERSIBLE DATA HIDING IN ENCRYPTED IMAGES BY RESERVING ROOM BEFORE ENCRYPTION TECHNIQUE AND LSB MATCHING ALGORITHM

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REVERSIBLE DATA HIDING IN ENCRYPTED IMAGES BY RESERVING ROOM BEFORE ENCRYPTION TECHNIQUE AND LSB MATCHING ALGORITHM