| Summary: | 碩士 === 國立東華大學 === 資訊工程學系 === 97 === Due to fast growth of Internet application, more and more multimedia data are
transmitted via Internet, especially digital images. Due to the insecurity of Internet,
digital images can be easily retrieved, copied and tampered. Thus, how to protect digital
images is an important issue. The (k, n) secret image sharing scheme is a kind of digital
image protection scheme, which distributes a secret image into n shadow images and
the secret image can be reconstructed from any k (k≤n) shadow images.
Recently, Wang et al introduced a new type of (2, n) scalable secret image sharing
(SSIS) scheme, which can gradually reconstruct a secret image in a scalable manner in
which the amount of secret information is proportional to the number of participants. In
this paper, we propose two approaches for constructing the (k, n)-SSIS schemes.
Approach 1 and Approach 2, respectively, have shadow with sizes 1/n times and 1/k
times that of the secret image. A (2, n)-SSIS scheme using Approach 1 has lesser
shadow size than Wang et al’s (2, n)-SSIS scheme, which is more suitable for faster
transmission in a distributed multimedia system. On the other hand, Approach 2 is
reduced to Wang et al’s (2, n)-SSIS scheme for k=2. Although the authors claim that
their (2, n)-SSIS scheme can be easily extended to the general (k, n) scheme, the
extension is not that easy as the authors claim. For the completeness of a (k, n)-SSIS
scheme, both approaches are introduced.
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