（3, n）－－門檻式視覺機密分享之新設計法

A Novel Design for 3 out of n Visual Secret Sharing Schemes

社會網絡分析為觀察線上網絡形成與探索虛擬社群變遷的重要工具，而在各種社會網絡分析方法中，區塊模式化則為分析網絡結構的關鍵方法，它不只可用於個別節點的位置與角色分析，也可用於發掘整體網絡的聚合次團體。傳統的區塊模式化以網絡的相鄰矩陣為操作目標，將相鄰矩陣盡量調整與分割為元素全為0 或全為1 的區塊，然後探討區塊之間的對應網絡結構。本研究則嘗試以相鄰矩陣經由布林運算所產生的可達矩陣作為區塊模式化擴展的操作目標，並以部落格朋友網絡為例說明此區塊模式化擴展的可能運用：藉由不同距離可達矩陣的區塊模式化，本研究可以分析各種以寬鬆聚合次團體為基礎的網絡結構；若以最長距離的可達矩陣為區塊模式化目標，則更可將網絡完美對應至領結結構，並呼應對稱無循環結構。

Social network analysis is an important tool to observe the formations of online networks and to explore the changes of virtual communities. Amongst the various methods of social network analyses, block modeling is a key approach to analyzing network structures. It can be applied not only to position and role analyses of the individual nodes, but also to cohesive subgroup discoveries of the whole network. Conventional block modeling, operating on the adjacency matrix of the network, tries to adjust and partition the adjacency matrix into blocks that contain all 0s or all 1s approximately, and to investigate the network structure between the approximate blocks. In this research, we apply boolean matrix operation on the adjacency matrix to generate the reachability matrix as the extended target of block modeling. And we use a blogroll network to show the possible applications of the extended block modeling. Via reachability matrices of different distances, we can analyze the network structures based on a variety of loosely cohesive subgroups. Via the longest reachability matrix, we can fit the network perfectly into the bowtie structure, and the fit is also corresponding to the symmetric-acyclic structure.