Title of thesis A Hybrid Chaotic Image Encryption Scheme ...

Title of thesis A Hybrid Chaotic Image Encryption Scheme Based on S-Box

and Ciphertext Feedback

I, MUHAMMAD ASIM

hereby allow my thesis to be placed at the Information Resource Center (IRC) of

Universiti Teknologi PETRONAS (UTP) with the following conditions:

1. The thesis becomes the property ofUTP.

2. The IRC ofUTP may make copies of the thesis for academic purposes only.

3. This thesis is classified as

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0 Non-confidential

If this thesis is confidential, please state the reason:

The contents of the thesis will remain confidential for _____ years.

Remarks on disclosure:

l./ S1gnature of Author

Permanent: Moh. Baba Kheel, Village: Gujar Garhi Address Tehsil & District: Mardan, Prov: N. WF.P

Pakistan

Date:

Endorsed by

Signature of Supervisor

Name of Supervisor Assoc. Pro[ Dr. Varun Jeoti

UNIVERSITI TEKNOLOGI PETRONAS

Approval by Supervisor

The undersigned certify that they have read, and recommend to The Postgraduate Studies

Programme for acceptance, a thesis entitled

A Hybrid Chaotic Image Encryption Scheme

Based on S-box and Ciphertext Feedback

submitted by

Muhammad Asim

for the fulfilment of the requirements for the degree of

Masters of Science in Electrical and Electronic Engineering

'23 ,- b] - ?.o-ol­Date

Signature

Main Supervisor

Date

Co-Supervisor

\)~-Assoc. Pro( Dr. Varun Jeoti

II

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UNIVERSITI TEKNOLOGI PETRONAS

A Hybrid Chaotic Image Encryption Scheme

Based on S-box and Ciphertext Feedback

By

Muhammad Asim

A THESIS

SUBMITTED TO THE POSTGRADUATE STUDIES PROGRAMME

AS A REQUIREMENT FOR THE

DEGREE OF MASTERS OF SCIENCE IN ELECTRICAL AND ELECTRONIC

ENGINEERING

Electrical and Electronic Engineering

BANDAR SERI ISKANDAR,

PERAK

May, 2007

lll

DECLARATION

l hereby declare that the thesis is based on my original work except for quotations and

citations which have been duly acknowledged. I also declare that it has not been

previously or concurrently submitted for any other degree at UTP or other institutions.

j . "' Signature: /t\-~'"''?:

[7 I

Name : Muhammad Asim

IV

ACKNOWLEDGEMENT

First of all I wish to thank ALLAH who provided me the courage and strength that

enabled me to complete this work.

I would like to acknowledge the immense contributions, guidance and encouragement

from my supervisor Assoc. Prof. Dr. Varun Jeoti. He has been a mentor and also friend to

me. Throughout the whole duration of this work, I have learnt much from him, not only

in terms of technical knowledge but also the finer points of being a better researcher.

Without his guidance, this work would not have yielded such positive results and

published at international levels. Indeed his dedication is such that it surpasses

boundaries of office hours as evident by the hours of personal time that he has spent with

me in discussions of the research work.

I would also like to thank Dr. Shujun Li from Xi'an Jiantong University for very helpful

discussions, reviews and comments on our proposed schemes. He is an expert in the field

of chaotic cryptography and cryptanalysis but yet he displayed such willingness to help a

beginner like me and answered my questions regularly. I feel highly privileged to be able

to co-author one paper with him on the security of a recently proposed cipher by Pareek

et a!. in [Pareek et a!., 2006].

I am grateful to the fellow postgraduate students and undergraduate students in UTP that

have been through the thick and thin with me throughout the duration of my pursuit for

this Master degree. They have been constant sources of encouragement and

companionship in times when the going was getting very tough. Their friendships are

likened to rare gems.

I would like to pay the most smcere thanks to my parents, whose teaching,

encouragement and education, enabled me to pursue achievement in research. I would

also like to thank my uncle Mr. Mian Unwan-Ud-Din, from whom I got instruction on

v

each and every step, whenever I got struck. I would also like to thank my dearest friend

Mr. Aimal Hayat for his continuous support during my pursuit of this Master degree.

VI

ABSTRACT

The fascinating developments in digital image processing and network communications

during the past decade have created a great demand for real-time secure image

transmission over the internet and through wireless networks. Due to some intrinsic

features of images, such as bulk data capacity and high correlation among pixels,

traditional encryption algorithms such as IDEA, DES and AES are not suitable for

practical image encryption, especially for real time applications. In order to meet these

challenges, a number of schemes have been proposed for encryption of digital images,

making use of chaotic dynamical systems.

The objective of the work undertaken in this thesis is two-fold - firstly to evaluate the

security of a few representative chaotic ciphers by performing the cryptanalysis on them

and secondly, to design an appropriate cipher that would fulfill the needs for both security

and speed.

The cryptanalysis is performed on two recently proposed chaotic ciphers by Pareek et a!. in

[Pareek et a!., 2005] and [Pareek et a!., 2006]. The first cipher is a generic chaotic block

cipher. It is shown that the proposed cipher is insecure against differential and known­

plaintext attacks. We also show that the key space size of the proposed cipher is less than

what is claimed by the authors. The second cipher of Pareek et a!. is a complete image

encryption scheme. This scheme is also shown insecure against the differential attack in the

thesis. It is also shown suffering from a few security defects and, therefore, is not suitable

for real time secure encryption of digital images.

In this work, a complete image encryption scheme - Hybrid Chaotic Image Encryption

Scheme (HyChiES) is designed. HyChiES is based on a cryptosystem consisting of

multiple piecewise linear chaotic maps (m-PLCMs), a generalized logistic map, AES S-box

and ciphertext feedback. The analysis of the HyChiES shows that it is extremely sensitive

to changes in pixels and, therefore, has an avalanche effect - a highly desirable property

for any cipher. As a result, HyChiES randomizes plain images very effectively.

VII