الفهرس 
Chapter 1: Cryptography and Cellular AutomataOnly 14 pages are availabe for public view
 |  | from | 32 |  |  |
| | | from | 32 | | |
Abstract
A long with the rapid development of Internet and universal application
of multimedia technology, more and more information including audio,
image, and other multimedia, has been transmitted over unsecured
channels. In particular, image security has attracted more and more
attention since images have been widely used in daily life. For example,
people use images including military photographs, and financial records
etc., to exchange all kinds of information.
Yet the main obstacle in the widespread deployment of digital
multimedia services has been enforcing security and ensuring authorized
access to sensitive data. A direct solution is to use an encryption algorithm
to mask the multimedia data streams. In this regard, traditional encryption
algorithms that based on celebrated number theory, algebra, and computer
arithmetic such as IDEA, AES, DES, RSA etc. could be used.
However, these encryption schemes have been invented to text
encryption and appear not to be ideal for image applications due to some
intrinsic features of images such as bulk data capacity, high correlation
between pixels and high redundancy, which are troublesome for traditional
encryption. Moreover, these encryption schemes require extra operations
on compressed image data, thereby demanding long computational time
and high computing power. In real time communication, because of their
low encryption and decryption speeds, they may introduce significant
latency.
In order to develop effective image encryption techniques, these have
to be fully understood. Recently, some researchers have pointed out that
there exists tight relationship between cellular automata (CA) and
v
cryptography. Many features of cellular automata, such as the periodicity,
mixing and the sensitivity to initial conditions, can be connected with the
“confusion” and “diffusion” property in cryptography. An elementary
cellular automaton (ECA) is the simplest class of one-dimensional cellular
automata, which is a linear array of cells with three neighborhood
dependency, and state of each cell is 0 or 1. Based on ECA, there are a
number of image encryption schemes have been proposed in the literature.
However, due to the lack of a strict scrutiny on the security, some of them
have been found insecure against various attacks.
This dissertation studies the security problems of some image encryption
schemes based on cellular automata to known the strength and weakness in
their design. In addition, we propose a new self adaptive image encryption
scheme based on 2D reversible memory cellular automata.
Research Objectives
This dissertation involves the following aspects about cellular automata
(CA) and cellular neural network ciphers (CNN): cryptanalysis of the
recently-proposed ciphers based on cellular automata and designs a new
image encryption that overcomes the weakness of the previous schemes.
vi
The main contribution of this dissertation can be summarized as
follows:
1. Analyze the scheme based on elementary cellular automata (ECA)
proposed in [72] .Based on the given analysis, it is demonstrated that
the scheme under study can be broken by several attacks. Similarly,
analyze the image encryption based on elementary cellular automata
proposed in [77] Based on the given analysis, we report the
following problems: a) the scheme is not sensitive with respect to
both the changes of plain-images and key streams generated by
ECA; b) the scheme can be broken by various cryptanalysis. (The
above contribution has been published in the journal of Advanced
Materials Research)
2. It’s demonstrated that the scheme of [95], the scheme for Image
Encryption based on Cellular Automata and Arnold Cat’s map, is not
secure against the following attacks: known plaintext and chosen
plaintext. In addition the scheme is insensitive to the change of the
secret plain-image.
3. Design Self-Adaptive Image Encryption Based on 2D Reversible
Memory Cellular Automata. We propose a novel secret image
encryption scheme based on two dimensional cellular automata with
reversible transition function.
The thesis organized into four chapters as follows:
Chapter one gives an overview of cryptography, cellular automata and
cellular neural network.
vii
Chapter two gives the proposed cryptanalysis of the main recently
schemes based on elementary cellular automata [72, 77, 95].
Chapter three gives the proposed image encryption scheme based on 2D
reversible memory cellular automata and cellular neural network.
Chapter four gives the conclusion and future works.
viii
TABLE OF