Abstract:
Information security has been an important issue for humanity in every age.
But nowadays, the diversification of communication facilities, especially the rapid
development of the Internet, has made it possible for this need to reach the highest
level.
Cryptography is one of the most important tools to meet the need for information
privacy. Since it was invented, cryptography techniques are constantly changing
in parallel with the change in the communication channel used and the type of
information transmitted. Nowadays, a wide range of secure cryptographic methods
are developed and used.
However, standard encryption algorithms show different efficiencies according to the
type of encrypted data and the compatibility of these methods with different file types
are discussed. Especially multimedia files have different features than text files and
these features have several advantages and disadvantages in encryption. For this
reason, cryptography of image files is examined as one of the special subdivisions
of cryptology.
Image data can be encrypted with conventional block encryption or chain encryption
algorithms. But this is not efficient enough due to the large size of the data, the
strong correlations between the pixel values and the high redundancy. For this reason,
different methods for image encryption have been proposed over the years. The
chaotic methods have been tried and tested since it is more than adequate for image
xiv
encryption.
Chaotic functions can be integrated into image encryption in a variety of ways and
can be used for a variety of purposes. One of them is the mixing of the picture with
a chaotic map. Researchers have observed that confusion and diffusion requirements
in encryption can be met by using chaotic maps and have shown particular interest in
this technique.
In this thesis, a new algorithm is proposed using Lorenz maps and YCbCr color space
transformation for encrypt a colored image. Algorithm was constructed to cover
encryption and decryption processes and reliability was examined with various tests.
It is also proposed what can be done for efficiency and development. Thus, a unique
method that can be used for image encryption has been try to developed.
