The secret data should stay hidden in a host signal, even if that signal is subjected to manipulations as filtering, resampling, cropping, or lossy data compression. Since no one method

is capable of achieving all these goals, a class of processes is needed to span the range of

possible applications, Trade-offs exists between the quantity of data and the immunity to modification ..Many RDH methods have been proposed since it was introduced, Xinpeng Zhang

proposed separable reversible data hiding in encrypted images. In the first phase, a content

owner encrypts the original uncompressed image using an encryption key. Then, a data-hider

may compress the least significant bits of the encrypted image using a data-hiding key to create a sparse space to accommodate some additional data( i.e.,Vacating Room After Encryption

(VRAE) method). With an encrypted image containing additional data, if a receiver has the

datahiding key, he can extract the additional data though he does not know the image content.

If the receiver has the encryption key, he can decrypt the received data to obtain an image

similar to the original one, but cannot extract the additional data

2.2 Reversible Data Hiding

Reversible data hiding algorithm, which can recover the original image without any distortion

from the marked image after the hidden data have been extracted

2.2.1 Embedding Algorithm With One Zero Point and One Peak Point

In the histogram, we first find a zero point, and then a peak point. A zero point corresponds

to the grayscale value which no pixel in the given image. A peak point corresponds to the

grayscale value which the maximum number of pixels in the given image. The objective of

finding the peak point is to increase the embedding capacity as large as possible. The whole

image is scanned in a sequential order, say, row-by-row, from top to bottom, or, column-byJyothi Engineering College, Cheruthuruthy Dept. of CSE,December 2015

Secure Data Transmission Through Reversible Data Hiding 4

column, from left to right. The grayscale value of pixels between 155 (including 155) and

254 (including 254) is incremented by 1. This step is equivalent to shifting the range of the

histogram, [155 254], to the right-hand side by 1 unit, leaving the grayscale value 155 empty.

The whole image is scanned once again in the same sequential order . If the corresponding

to-be-embedded bit in the sequence is binary 1, the pixel value is incremented by 1. Otherwise,

the pixel value remains intact

2.2.2 Pseudocode Embedding Algorithm

The zero point defined above may not exist for some image histograms. The concept of minimum point is hence more general. The minimum point, we mean such a grayscale value, that a

minimum number of pixels assume this value, i.e., is minimum. . A peak point corresponds to

the grayscale value which the maximum number of pixels in the given image. The algorithm is

quite simple, and the execution time is rather short. Therefore, its overall performance is better

than many existing reversible data hiding algorithms

2.3 Efficent Compression of Encrypted Gratscale Images

Lossless compression of encrypted sources can be achieved .A resolution progressive compression scheme which compresses an encrypted image progressively in resolution . The data

is usually first compressed and then encrypted at the sender side; to recover the data at the

receiver side, decryption is performed prior to decompression. However, in some application

scenarios, this conventional diagram needs to be revisited.

Suppose Alice needs to send information to Bob, while Charlie is the network

provider. Alice wants to keep the information confidential to Charlie; however, the resources

that she has is too limited to perform compression. So, Alice just encrypts the data using a

simple cipher and gets it forwarded. Charlie, as the network provider, always has the interest to

reduce the data rate. That is, it is desirable for Charlie to perform compression without having

access to the secret key. The overall system performance can be as good as the conventional

approach. That is, neither the security nor the compression efficiency will be sacrificed by performing compression in the encrypted domain.

Jyothi Engineering College, Cheruthuruthy Dept. of CSE,December 2015

Secure Data Transmission Through Reversible Data Hiding 5

2.4 Unique Key Using Encryption and Decryption of Image

Image data security is the essential portion in communication and multi media world.

During storing and sharing, avoid third party access of data is the challenge one in the image

data security. Cryptography is the best technique of image data security. In Greek, crypto refers

Ã¢AIJhiddenÃ¢ Ë˜ AÂ§ and graphy refers Ã¢ Ë˜ AIJscriptÃ¢ Ë˜ AÂ§. Cryptography has two processes namely en- Ë˜

cryption and decryption. Encryption achieves the conversion by possessing a key of original

data into unreadable form called encoding. Restoring of encrypted data in to original is decoding or decryption.

Encryption and decryption attain by single key is the previous finest technique of

image security. Single key assigned for image encryption and it is encoded. Then the key is

send via secure way for decryption purpose. Subsequently the key is safely received and apply

decryption process and obtain original image.

2.5 Separable Reversible Encrypted Data Hiding in Encrypted Image Using AES Algorithm and BPCS Algorithm

Data hiding in image uses the AES algorithm and Lossy techniques. But instead of this we

use the AES algorithm and the BPCS technique. This gives security to the encrypted data which

is embedded in the image. In this user encrypt the data and encrypt the image then embedded

that data into the image and sends to the receiver very secretly we provide 2 keys at the time of

image encryption and for data encryption. The both keys are uses same for Decryption process.

User can decrypt the both image and data.

2.6 Image Encryption Decryption with Symmetric Key Cryptography using MATLAB

Cryptography is the practice and study of hiding information. In modern times cryptography is considered a branch of both mathematics and computer science and is affiliated closely

with information theory, computer security and engineering. Cryptography is used in appliJyothi Engineering College, Cheruthuruthy Dept. of CSE,December 2015

Secure Data Transmission Through Reversible Data Hiding 6

cations present in technologically advanced societies; examples include the security of ATM

cards, computer passwords and electronic commerce, which all depend on cryptography. There

are two basic types of cryptography: Symmetric Key and Asymmetric Key. Symmetric key algorithms are the quickest and most commonly used type of encryption. Here, a single key is

used for both encryption and decryption. There are few well-known symmetric key algorithms

i.e. DES, RC2, RC4, IDEA etc.

2.7 Reversible Data Hiding in Encrypted Image

The reversible data hiding scheme for encrypted image. After encrypting the entire data

of an uncompressed image by a stream cipher, the additional data can be embedded into the

image by modifying a small proportion of encrypted data. With an encrypted image containing

additional data, one may firstly decrypt it using the encryption key, and the decrypted version

is similar to the original image. According to the data-hiding key, with the aid of spatial correlation in natural image, the embedded data can be successfully extracted and the original image

can be perfectly recovered.

2.8 Image Encryption and Decryption using Modified Hill Cipher Technique

The main objective of proposed algorithm is to encrypt an image using a technique different from the traditional Hill Cipher. In this paper a Modified Hill encryption and decryption

technique has been proposed which uses an involuntary key matrix. The scheme is a fast encryption scheme which provides a solution of problems of encrypting the images with homogeneous background. Proposed algorithm for encrypting and decrypting images is quite reliable

and robust. In proposed algorithm we generate a function which select a random key matrix

and then encrypt the image using the key matrix. For the decryption we again use this key

matrix to get the original image.

Jyothi Engineering College, Cheruthuruthy Dept. of CSE,December 2015

Secure Data Transmission Through Reversible Data Hiding 7

2.9 Image Encryption Using Binary Key images

The image encryption using a binary key-image. The key-image is either a bit plane or

an edge map generated from another image, which has the same size as the original image to

be encrypted. In addition, we introduce two new lossless image encryption algorithms using

this key-image technique. The performance of these algorithms is discussed against common

attacks such as the brute force attack, ciphertext attacks and plaintext attacks. The analysis and

experimental results show that the proposed algorithms can fully encrypt all types of images.

This makes them suitable for securing multimedia applications and shows they have the potential to be used to secure communications in a variety of wired/wireless scenarios and real-time

application such as mobile phone services

2.10 An Improved Reversible Data Hiding in Encrypted Images Using Side

Match

A better scheme for measuring the smoothness of blocks. An encrypted image into blocks,

and each block carries one bit by flipping three LSBs of a set of pre-defined pixels. The data extraction and image recovery can be achieved by examining the block smoothness. ZhangÃ¢A Ë˜ Zs Â´

work did not fully exploit the pixels in calculating the smoothness of each block and did not

consider the pixel correlations in the border of neighboring blocks. These two issues could

reduce the correctness of data extraction. Use the side-match scheme to decrease the error rate

of extracted-bits.The four borders of each block do not join the calculation of block smoothness.Decrease the rate of correctness of data extraction, especially when the block size is small

Jyothi Engineering College, Cheruthuruthy Dept. of CSE,December 2015

Secure Data Transmission Through Reversible Data Hiding 8

CHAPTER 3

RESEARCH METHODOLOGY

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