| Summary: | 碩士 === 國立東華大學 === 資訊工程學系 === 102 === Through Internet and social network, digital multimedia can be rapidly delivered and shared in network. Therefore, protecting digital image is an important issue. Secret image sharing (SIS) combines methods and techniques from cryptography and image processing. A SIS scheme shares a secret message into shadow images, which are referred to as shadows, in the way that if shadows are combined in a specific way, the secret image can be recovered. SIS scheme is usually implemented as a threshold (k, n)-SIS scheme, where k≤n, that divides a secret image into n shadows. By collecting any k shadows, we can reconstruct the secret image, but use of (k1) or fewer shadows will not gain any information about the secret image.
The most important category of (k, n)-SIS scheme is based on Shamir’s (k, n) secret sharing. In (k, n)-SIS scheme, we embed secret pixels into all coefficients in (k1)-degree polynomial to share the secret image and meantime reduced shadow size to 1/k of secret image size. However, this polynomial-based (k, n)-SIS scheme needs permuting the pixels of secret image. If we do not permute secret image first, there will be a problem of remanent secret image on shadows.
In this thesis, we adopt Reed Solomon code, a maximum distance separable code, to propose a (k, n)-SIS scheme. Our (k, n)-SIS scheme solves the problem of remanent secret image on shadows, and does not need permuting secret image. Meantime, we can reduce the shadow size like polynomial-based (k, n)-SIS that reduces shadow size to 1/k of secret image size. Since the Reed Solomon code is based on Galois Field GF(2^8), our reconstructed image is distortion-less.
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