| Summary: | 碩士 === 國立東華大學 === 資訊工程學系 === 98 === In a (k, n) visual cryptography scheme (VCS), a secret image is encoded into n shadow images that distributed to n participants. Any k participants can reveal the secret image by stacking their shadow images to visually decode the secret image without the help of hardware or computation, but (k-1) or fewer participants will not gain any information. This distinctive property of easy decoding by the human visual system can be used to securely and cheaply share any printed-text secret image- such as a password- in situations where no computer assistance is available or desirable. Due to the uniqueness of VCS and more visual data in the modern visual communication, there will be more and more intended applications of VCS in the future. Up to now, the VSS technology has been adopted in many applications such as digital image indexing, watermarking, securing display, embedding private information.
Most researches on VCS are to share one secret only, and this limits its possible applications. In this thesis we consider the case when the secret image is more than one, and this is a so-called multi-secret VCS (MVCS). The previous works on MVCS are all the simple 2-out-of-2 cases. We consider a general (k, n, s)-MVCS for any k, n and s using ringed shadows. This thesis has three main contributions: (1) our scheme is the first general (k, n)-MVCS, which can be applied on any k and n (2) we give the formal security and contrast conditions of (k, n)-MVCS (3) we theoretically prove that the proposed (k, n)-MVCS satisfies the security and contrast conditions.
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