| Summary: | 碩士 === 國立東華大學 === 資訊工程學系 === 101 === In a (k, n)-VCS, any k participants can print out their shadows on transparencies
and stack them on an overhead projector to visually decode the secret image without
computer hardware or computation.
Recently, Hou et al. introduced a (2, n) block-based progressive visual
cryptographic scheme (BPVCS), which the image blocks can be gradually recovered
step by step. In Hou et al.’s (2, n)-BPVCS, a secret image is subdivided into n
non-overlapped image blocks. When stacking any t (2 t n) shadows, all the image
blocks associated with these t participants will be recovered. Unfortunately, Hou et al.’s
(2, n)-BVCPS suffers from the cheating problem, which any two dishonest participants
might collude together to tamper their image blocks shared with other honest
participants. Also, they can impersonate an honest participant to force other honest
participants to reconstruct the wrong secret.
In this thesis, we solve the cheating problem and propose a cheating immune (2,
n)-BPVCS. Additionally, Hou et al.’s scheme is only suitable for the 2-out-of-n case, i.e.,
(k, n)-BPVCS where k=2. Here, we also present a (k, n)-BPVCS. The problem we
consider in this thesis is that of constructing the cheating immune BVCPS that are
robust against dishonest participants.
This thesis has four main contributions: (1) we provide two cheating types in Hou
et al.’s (2, n)-BPVCS (2) we propose a cheating immune (2, n)-BPVCS (3) we propose
a general cheating immune (k, n)-BPVCS, where k and n can be any integers (4) our (2,
n)-BPVCS and (k, n)-BPVCS are theoretically proven to satisfy the progressive
recovery, the security, and the cheating immune capability.
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