الفهرس 
CHAPTER 1 BACKGROUNDOnly 14 pages are availabe for public view
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Abstract
Secret Sharing is one of the efficient methods for secured transmission of data. This thesis provides a basic idea about Secret Sharing, what is it and how the Secret Sharing schemes are constructed and implemented in diversified fields. The secret data adopts secret sharing scheme, from the point of view of data, which guarantees the availability and secrecy of secret data in multiple aspects and multiple levels. In secret image sharing schemes, the shadow images are generated such that a sufficient number of shadow images can cooperate to reconstruct the secret image. In the process of reconstruction, of shadow images can recover the secret image easily, but less than images cannot recover the secret image.
Traditional image secret sharing schemes shared secret image into shadows images based on Lagrange interpolation polynomial. The most important drawbacks of these schemes are computation complexity and distortion of recovered image.
Cellular automata are the best solution of image secret sharing to overcome these drawbacks.
An elementary cellular automaton is the simplest class of one-dimensional cellular automata. Elementary cellular automata are used in image cryptosystems because of its low computational cost and simplicity of hardware implementation. Based on a special kind of periodic boundary cellular automata with unity attractors, a new secret image sharing scheme is proposed.
The basic idea of the proposed scheme is that the secret image can be shared based on the bitwise XOR operation between the pixels of the secret image and chosen secret states of a selected secret unity attractor, where the results are XORed with a random grid matrix to give a randomness measure for the shared images. Because the proposed scheme only uses integer arithmetic and logical operations, it is simple and has a linear computational complexity. Using colored and gray images, experimental and formal analysis of the proposed scheme indicates its correctness and effectiveness.
Using of multiple shares for encoding one secret image increases the communication overhead, so multi-secret sharing schemes have been introduced to be a better solve to the problem.
We propose a multi secret sharing scheme using Blackley secret sharing and Hill cipher as encoded algorithm. In comparison with Jothi scheme we find that we do not use random grid as share image. Also, a threshold secret sharing method using Blakely concept which only or more of shadow images can reconstruct all secret images, so it will decrease the network overflow. Also Using Hill Cipher and Blakley to share more than secret image increases the security of secret images with lossless image recovery and no pixel expansion. Experimental results demonstrate the efficiency of the scheme.