Cheating Immune Block-based Progressive Visual Cryptography

• Main Authors: Yi-Chin Lin, 林易青
• Other Authors: Ching-Nung Yang
• Format: Others
• Published: 2013
• Online Access: http://ndltd.ncl.edu.tw/handle/70757100531708692175

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.