| Summary: | 碩士 === 元智大學 === 資訊工程學系 === 98 === The thesis proposes a visual cryptography (VC) scheme with identifiable shares. In the proposed (t, n), 2 ? t ? n sharing method, the input image O is encoded in n shares that exhibits the following features: (1) each share is the same scale as O and has noise-like appearance, (2) stacking t?1 or less shares reveals no secret, (3) the secrets can be revealed by superimposing t or more shares, (4) folding a share up can disclose some tag patterns, and (5) both of the secret information and the tag patterns are recognized by naked eye without any computation. The property to show up tag patterns on folded shares is a new concept in visual cryptography scheme. The tag patterns provide diverse capabilities to the VC scheme, such as (1) augmented message to the secret information, (2) a simple and user-friendly interface for managing the numerous shares created by VC schemes, and (3) evidence for verifying consistency among those shares cooperating in a decoding instance. A (2, 2) sharing scheme using random grids and another (t, n) VC method based on probabilistic VC are implemented. Simulation results show that both the revealed secret messages and tag patterns can be recognized easily by naked eye, and no regular patterns are appeared if less than t shares are stacked, demonstrating the feasibility and high security of the proposed scheme.
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