In this thesis, we implement a (k, n) secret image sharing algorithm based on Thien and Lin’s scheme with modifications to reduce some distortion. The secret image is processed and split into n shadow images. We can reconstruct the secret image by using Lagrange interpolation when we collect k or more shadow images. Firstly, we propose an elegant method using the concept of generators in a multiplicative cyclic group to shuffle the secret image. The security is based on the difficulty of solving the discrete logarithm problem. We also present a truncated method to reduce the truncation distortion. We replace zero points in the range [0, 250] with those grayscale of pixels greater than 250 with positions of zero occurrences under 251. Experimental results show that the proposed method can suffer from the truncation distortion while preserves the security.

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[web01]http://en.wikipedia.org/wiki/Lagrange_interpolation, last access on May 27, 2010.
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