IRJET- An Acute Method of Encryption & Decryption by using Histograms and Cheat Images

International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056
Volume: 05 Issue: 06 | June-2018 www.irjet.net p-ISSN: 2395-0072
© 2018, IRJET | Impact Factor value: 6.171 | ISO 9001:2008 Certified Journal | Page 628
AN ACUTE METHOD OF ENCRYPTION & DECRYPTION BY USING
HISTOGRAMS AND CHEAT IMAGES
Ashish Kumar Singh ,Madan Kushwaha , Abhishek Kumar
1Assistant Professor, Department of CS&A,, Krishna Institute of Technology ,Kanpur Uttar Pradesh, India
2,3Assistant Professor, Department of CSE, Bansal Institute of Engineering & Technology, Uttar Pradesh, India
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Abstract - Images are different from textual data in many
aspects such as highly redundancy and correlation, the local
structure and the characteristics of the amplitude-frequency.
The conventional encryption techniquescannotappliedtothe
images. As a result, image encryption came into play to
perform cryptographic operations on images. In recent years,
lots of work did in this area. In this paper, we propose an
image encryption technique based on logistic map and cheat
image. Cheat images used in this technique are the images
selected from the public network together with the chaotic
matrices generated by the logistic map. Encryption and
Decryption, both processes requirethecheatimagetoperform
their task. The proposed encryption technique is secure and
robust enough in practicalcommunicationfromtheviewpoint
of the computer experiments such as cheat characteristic
analysis, differential attack analysis, sensitive analysis and
statistical analysis.
Key Words: Image Encryption, Logistic Map, Cryptography,
Cheat Image.
1.INTRODUCTION
By the rapid development of the Networking systems
allowed large files such as digital images to be easily
transfers over the network. And for this reason, there is a
need for Image Cryptography. Image cryptography consists
of encryption and decryption of images. Color Image is
basically consists of pixels which measure the intensity and
chrominance of light. The brightness information in each
spectral band is the actual information stored in digital
image data. Pixel values are correlated with the neighboring
pixels. One may easily guess the value of pixels from the
neighboring pixel values.
Information hiding and Encryption are generally two
approaches which are used to protect digital images.
Information hiding usually uses watermarking,
steganography, anonymity and cover channel whereas
encryption includes conventional encryption and others
such as chaotic encryption [1]. Ergodicity, mixing property
and sensitivity to initial conditions/system parameters are
some fundamental properties of chaotic system, are
analogous to some ideal cryptographic properties i.e.
confusion, diffusion, balance and avalanche properties.
Chaos-based cryptosystem has two iterative stages, In the
confusion stage, pixels are permuted but the values of pixels
are unchanged whereas in diffusion stage, the pixel values
are modified sequentially so that a tiny changeinonepixel is
spread out to many pixels, hopefully the whole image [2].
There are n permutation rounds in the confusion stage with
n>=1 are required to decorrelate the relationship between
adjacent pixels. To achieve a satisfactorylevel ofsecurity,the
whole confusion-diffusion roundsarerepeatedfora number
of times. Chaotic maps parameters governing the
permutation and the diffusion should better be different in
different rounds. Round key generatorwitha seedsecretkey
as input are used to achieve it
In this proposed scheme, we used the cheat image for the
encryption and decryption process. Cheat image are the
images selected from the public network.
1.1 LOGISTIC MAP-
The Logistic Map
Xn+1=a-xn
2
(2.1)
is the simplest one-dimensional mapdisplayinga singularity
which depends on a single parameter a[3]. Each value in the
range of the map ‘f’ has exactly two preimages, which will
prove to be a key ingredient to generate chaos. This most
important consequences of the singularity located at x=0 is
shown from its graph [fig 2.1(a)].

Figure 2.1: (a) Graph of the logistic map for a=2. (b)
Graphical representation of the iteration of (2.1).
As in the iteration (2.1), the action of the logistic map is
represented algebraically; it’s also represented
geometrically as in [fig 2.1(b)]. Logistic map displayed the
various behavior which are easily explored as this map
depends on a single parameter a. Two main types of
dynamical regimes can be observed: “stationaryorperiodic”
regimes and “chaotic” regimes. A finite setofdifferentvalues
that are forever repeated in fixed order are eventually
visited by the iterations in the first case. In the latter case,
the state of the system seemingly evolves in a disorder way
and never repeats itself exactly.
The logistic map is not only that the organization in
parameter space of these periodic and chaotic regimes can
be completely understood with simpletools,butthatdespite
of its simplicity it displays the most important features of
low-dimensional chaotic behavior.
1.2 CONFUSION AND DIFFUSION
Claude Shannon in his paper “Communication Theory of
Secrecy Systems”, published in 1949, identified that
confusion and diffusion are two properties of the operation
of a secure cipher. Confusion and Diffusion are two main
properties of an ideal cryptosystem. Confusion makes the
relationship between the plaintext and the cipher texts as
complex as involved as possible; diffusion has the property
that the redundancy in the statistics of the plaintext is
DISSIPATED in the statistics of the cipher text. In a cipher
with good diffusion, cipher text changed completely in an
unpredictable or pseudorandom manner if we change the
one bit of the plain text. The strict avalanche criterion states
that if we chose the ith bit randomly from the input and flips
it, then the probability that the jth bit of output will be
changed should be one half, for any i and j. Cipher text is
depend on the entire key and in different ways on different
bits of the key. In particular, if we change the single bit of the
key, cipher text changed completely. Correlation is reduced
between the plaintext and cipher text in the confusion
whereas the data located at some coordinates of the input
block are transposed to the other coordinates of the output
block in diffusion.
2. PROPOSED WORK
Selection of the platform, the language used etc. is the
important considerations in the implementation of any
software. The major implementation decisions that have
been made before the implementation of this project are as
follows-
a) Selection of the platform (operating system).
b) Selection of the programming language for
development of the application.
c) Coding guidelines to be followed.
Matlab (Matrix Laboratory), a fourth generation
programming language developed by MathWorks is a
numerical computing environment. It allows matrix
manipulations, plotting of functions and data,
implementation of algorithms, creation of user interfaces,
and interfacing with programs written in other lamguages,
including Fortan, C and C++ [4].
2.1 Permutation
In this process, we perform the permutation process on
input image and cheat image. We take the initial parameter
to perform the permutation task. These initial parameters
are used as a secret key to perform the permutation process
on the input image and cheat image. Both input and cheat
image are permutated using pixel permutation approach.
i. Encryption
Encryption is the process of transforming the information
using an algorithm to an unreadable form except those who
has special knowledge, usually referred as a key. In our
proposed approach, we take the input image together with
the cheat image. Cheat image is the image from the public
network and One can perform cryptographic tasks i.e.
encryption and decryption, if he has a knowledge of cheat
image. Same image is used as a cheat image in both
encryption and decryption process. In our approach,wejust
take the input image and cheat image, then we perform the
permutation process on the input image and cheat image.
Now, we generate the X0 from the cheat image using logistic
map. Now then, we generate the Q1 and Q2 from the X0
using the secret key parameters. Now, we generate the
encrypted image using Q1 and Q2.
ii. Decryption
Decryption is the process of converting data from
unreadable form into an original data thatisbeingencrypted
using key. The same key is used in both encryption and
decryption process. In decryption, we take the encrypted
image and apply the decryption algorithm together with the
same cheat image which we used at the time of encryption.
For decryption process, we

Experimental results
(a) (b)
(c) (d)
(e) (f)
(g) (h)
(i) (j)
(k) (l)
(m) (n)
(o)
(p)
(q) (r)

(s)
Fig 5 (a) plain image (b) correlation of plain image (c)
histogram of plain image (d) cheat image (e) correlation of
cheat image (f) histogram of cheatimage(g)permutedinput
image (h) correlation of permutedinputimage(i)histogram
of permuted input image (j) permuted cheat image (k)
correlation of permuted cheat image (l) histogram of
permuted. cheat image (m) X0 (n) correlation of X0 (o)
histogram of X0 (p) Q1 and Q2 (q) encrypted image (r)
correlation of encrypted image (s) histogram of encrypted
image.
2.2 SECURITY AND PERFORMANCE ANALYSIS
In this section, we will discuss the statistical analysis,
sensitivity analysis, differential analysis and cheat
characteristic analysis which is the main security
characteristics of the proposed encryption scheme. These
are the main concerns and needed to describe here because
a good encryption scheme should be robust against all kinds
of cryptographic, statistical and brute force attacks.
i. Statistical Analysis
We analyzedtheHistograms andcorrelationsof
two adjacent pixels in the cipher images to
prove the proposed cryptosystem against any
statistical attacks.
ii. Differential attack
To see the influence of changinga singlepixel in
the plain image on the encrypted image by the
proposed image encryption algorithm, pixels
change rate are calculated.
iii. Sensitivity analysis
Small change in the secret key would producea
completely different encrypted image i.e. An
ideal cryptosystem should be sensitive with
respect to the secret key. We observe that the
correlation coefficients are very small which
proves that the proposed cryptosystem is
highly key sensitive.
iv. Cheat characteristics analysis
Cheat image plays a very important role in this
proposed system in which it uses for both
encryption and decryption process. With the
only knowledge of secret key, one cannot
decrypt the image until he has knowledge of
cheat image.
v. Information Entropy Analysis
The information entropyvaluesofsomeimages
of USC-SIPI image database are calculated by
using (9).
3. CONCLUSIONS
An assistant image called cheat image is needed in the
encryption and decryption process. Cheat images are the
common images from the public network which are
neglected by the attackers. We choose the initial parameter
of the logistic map as a secret key. One cheat image isusedto
encrypt the number of plain images if it’s not attracting the
attention of the attacker. The experimental results are
shown and the performance analysis are described in detail
to demonstrate that the proposed encryption scheme is
robust and secure enough to be used in practical
communication.
REFERENCES
[1] Nisha Kushwah, Madhu Sharma, “Chaotic Map
Based Block Encryption”,IJCA(0975-8887)Volume
71-No. 16, June 2013
[2] J. Fridrich, “Symmetric ciphers based on two-
dimensional chaotic maps”, Int. J. Bifur. Chaos, vol.
8(6),1998, pp. 1259-1284. Intro first time Chapter
2
[3] CS 223B: “Introduction to Computer Vision”, Carlo
Tomasi- Stanford University.
[4] Linhua Zhang, Xiaofeng Liao, Xuebing Wang, “An
image encryption approach based on chaotic
maps”, Chaos, Solitons and Fractals 24(2005) 759-
765.
[5] N. Pareek, V. Patidar and K.K. Sud, “Image
encryption using chaotic logistic map”, Image.
Vision. Comput, vol. 24(9), 2006, pp. 926-934.
[6] K. W. Wong, BS. H. Kwok and W.S. Law, “A Fast
Image Encryption Scheme based on Chaotic
Standard Map”, Phys. Lett. A, vol 372(15), 2008,pp.
2645-2652.
[7] E. Solak and C. Cokal, “Comments on ‘ Encryption
and decryption of images with chaotic map

lattices’,” Chaos, vol. 18(3), 2008, pp. 038101-
038103.
[8] D. Arroyo, S. Li, J.M. Amigo, G. Alvarez and R.
Rhouma, “Comments on ‘Image Encryption with
Chaotically Coupled Chaotic Maps’,” Physica D, Vol
239(12), 2010, pp. 1002-1006.

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