الفهرس 
Chapter 1. IntroductionOnly 14 pages are availabe for public view
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Abstract
Cloud computing has emerged as a novel computing paradigm that offers great potential for storing data remotely. Presently, many organizations have
reduced the burden of local data storage and maintenance by outsourcing data
storage to the cloud. However, confidentiality and robustness of the outsourced
data continue to be a major concern for data owners. That is due to the lack of
control and physical possession over the data.
The secret sharing is considered one of the most feasible and efficient security
approaches to guarantee data confidentiality and robustness in the cloud. It is a
technique to share secrets among some shareholders. In that technique, the
shared secrets can be recovered only by certain authorized sets. This thesis
aimed to design new secret sharing schemes for securing data sharing over the
cloud to ensure both more confidentiality and more robustness.
The main contributions of this thesis can be summarized as follow:
1. Secret image sharing based on image encryption and chaotic map
lattices is proposed. Encryption on the secret images by using multiple
chaotic systems is applied. After that, sharing the encrypted images by
using one way coupled map lattice, which protect both confidentiality
and loss-tolerance simultaneously in sharing images over unsecured
channel has been done.
(The above contribution has been published in journal of Security and
its applications).
2. Lossless secret image sharing based on integer discrete cosine transform
is proposed. The original image is transformed firstly into the frequency
domain using IntDCT, which is operated on each block with size of 8*8.
Additionally, it generates the DCT shadows which are shared using
Shamir’s polynomial secret sharing method. After that the shadows are
transmitted through the network. During this transmission
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confidentiality has achieved on the recovered images without any
distortion and robustness against any malicious modifications in the
shadow images. (The above contribution has been accepted in
international conference).
The organization of this thesis is as follow:
Chapter one is an overview of cloud computing. It explains the
fundamental models, services security issues. Then, basic concepts and
properties of secret sharing. Finally, the chapter ends with reviewing some
of the recently proposed scheme.
Chapter two is the confidentiality and loss-tolerance for the media data by
sharing the original data into several shadows by using secret image
sharing. This is based on chaotic map lattices and applied some statistical
performances like, PSNR, HS and SSIM to evaluate the results of images
that are used. (Contribution 1).
Chapter three is the confidentiality on the recovered images without any
distortion and robustness against any malicious modifications in the shadow
images. This task implemented by using the integer discrete cosine
transform (IntDCT) on the secret image and then the shadows are
transmitted through the network. (Contribution 2).
Chapter four is the conclusions and future works.