無線隨意網路是由一群自主性的節點，彼此之間不需要有線的基礎網路設施，而是透過無線傳輸互相連結而成。無線隨意網路中的每一個節點，可以自由地移動並且參與資料的傳輸。此網路有著開放的特性，只要在範圍內的節點皆可以接收到訊息；此外，無線隨意網路又有著可移動性與無集中管理節點的特性，相較於有線網路在維護安全性的困難度更高，因此在傳播資料的防護上有著相當大的挑戰。
本論文提出了三個方法，來提升無線隨意網路資料傳播的安全性。第一個方法是以祕密分享為基礎，提出了多層次與群組的概念，符合無線隨意網路有著動態拓樸與無集中管理節點的特性，以達到金鑰對的產生與驗證；在此的架構中，所有的節點可以參與金鑰對的生成與驗證，並且不同層次的節點有著不同的身分，在較高層次的子群組中廣播的訊息，不會有遭受群組外一般節點竊聽的風險。第二個方法是以規範式入侵偵測與雙節點(two-hop)的方法來驗證路由資訊的完整性，確保路由資訊在無線隨意網路的傳播途中，不會遭受竄改。最後，本文提出了以字母為基礎的視覺化秘密分享方法，分享的秘密可以有意義的文字來取代原本的無意義像素點，藉以欺騙混淆竊聽者。此方法不需要複雜的運算，且接收者不需具備密碼學等知識背景也可運用；將分享的密文以重疊方式解密，符合門檻條件的接收者即可解讀隱藏的訊息；而竊聽者即使攔截到封包，在未符合門檻的條件下，也無法取出隱藏的資訊。因此，我們可以透過此三種方法來提升無線隨意網路在傳播資料上的安全性。

A Mobile Ad-Hoc NETwork (MANET) is established among a group of autonomous nodes that communicate with each other using a multi-hop radio network which maintains connectivity in an infrastructure-less environment. Each node is free to move independently and participates in forwarding data for other nodes. Unlike wired networks, there is no fixed and dedicated link available between the nodes. So any node within radio range can serve as access between nodes. This nature of open medium makes MANET difficult to restrict access and also it attracts malicious users who sniff or cheat other normal users. In addition, the dynamic and non-centralized features of MANET make it more difficult to implement security mechanisms than in traditional wired networks.
In this dissertation, we propose three mechanisms to enhance the security of data dispersion in MANET. First, a (n, t, n) secret sharing method is applied towards a group-based mobile network architecture to provide authentication and key management services. All nodes participate in key pair generation as shareholders using a threshold secret sharing scheme. This group-based network consists of multi-level participants. The nodes participating at different levels have different identities. The node identity in a higher-level subset is different from the larger common group. In the subset, shared information is broadcast efficiently and securely without risk of eavesdropping from the larger group.
Secondly, we propose a specification based intrusion detection scheme (SIDS) with the concept of two-hop integrity stamping (THIS) which utilizes previous hop routing messages to assure the integrity of the routing message. The vulnerable message fields that could be tampered with during dispersion are protected by this method. The proposed scheme is lightweight and deployable in a distributed and mobile environment. When employing the designed idea into the AODV routing protocol, experimental results demonstrate suitable performance in MANET.
Finally, we present a Letter-based Visual Cryptography Scheme (LVCS) where pixels are replaced by letters for the share images. Shares can be constructed using meaningful data as subterfuge while carrying secret data in plain sight, and an adversary will not recognize them as containing secrets. The secret information only can be reconstructed when the threshold condition is satisfied. Otherwise, eavesdropping reveals nothing even if the packet with secret shares is sniffed. In addition, LVCS has a novel stack-to-see property which requires neither knowledge of cryptography nor complex computations for decryption. It can decrease the resource consumption of encryption and decryption. Therefore, we apply these three schemes to raise the security of data dispersion in MANET.

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