الفهرس 
Chapter 1: IntroductionOnly 14 pages are availabe for public view
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Abstract
Security is an integral part of every technology in the information society,
today. Image transmission through wireless networks need both security and
reliability. Ciphering is the most widespread form of secure communication, while
coding achieves reliability. Traditional encryption schemes cannot fulfill the
requirements of image encryption due to its intrinsic features such as bulk data
capacity, high correlation among pixels and high redundancy, which are generally
difficult to handle by traditional methods. Chaos-based image encryption has certain
properties, which lead it directly to image encryption. In this thesis, firstly, a chaotic
encryption algorithm is introduced, whose key depends on an initial key and a plain
image to solve the problem of the short periodicity of the chaotic key stream. After
that, two hybrid ciphering schemes were proposed based on diffusion and confusion.
The encryption process of the first scheme is carried out in the spatial domain, while it
is carried out in the transform domain in the second scheme to achieve a large degree
of randomization. The Quadratic chaotic map is also improved with increasing its
chaotic parameter range to infinity to satisfy the security requirements. Furthermore,
the improved Quadratic maps were applied on a chaotic encryption scheme with
comparison with different traditional and chaotic encryption methods. A combined
ciphering and coding scheme is proposed based on the chaotic maps proposed in this
thesis with Low Density Parity-check Code (LDPC) to overcome the limitation of
noisy channels in the communication of encrypted images. Moreover, the
transmission of encrypted images using different chaotic maps over Raptor-OFDM
system through multipath fading channels is studied to overcome the drawbacks of
LDPC in the case of small block sizes. This system is important to determine which
chaotic map is more robust against the limitations of multipath fading channels.
Eventually, security and protection of human biometrics are very important issues,
since the biometrics are permanently associated with a user and cannot be replaced if
stolen. Cancelable biometric templates were used with the different chaotic
encryption schemes introduced in this thesis as a good practical application of the
proposed work in the field of security. These encryption schemes are used for
protecting fingerprint images instead of a simple random number generator used
before to overcome the loss of randomness in the case of a large number of users.