摘要
我們在此篇論文當中針對無線感測網路中的四個重要安全議題做討論，並且提出對應的更有效率的解決方案。問題本身的描述與對應的解決方案將在以下分別說明。 首先，金鑰交換是最基本的安全元素。但是因為在無線感測網路當中，其計算與通訊資源相當稀少，所以在一般電腦上所使用的金鑰交換機制無法直接在感測節點上使用。有鑑於此，我們提出了一個叫做CARPY與其變形，叫做CARPY+的金鑰交換機制。對比於其他現有的金鑰交換方法，我們所提出的方法更具安全性也更有效率。其中值得特別一提的是我們的方法是無需訊息交換就能建立出金鑰的。這將大大地降低了能量消耗。 另外，而一般的無線感測網路很容易就被惡意者輸入假資料。這是一種阻斷式攻擊，因為無線感測網路的電量通常有限，而如果感測節點再把寶貴的電量浪費在傳輸這些無用的假資料上的話，雖然到最後他們都會被檢查出來是假的而不會真的對網路使用者造成影響，但是卻會大大地減少無限感測網路的使用壽命。因此我們提出了一個稱之為CFAEF的機制來濾除網路中的假資料。這個機制的特點是一旦假資料被放入網路中，無需等待很久，感測節點即會偵測出所傳輸的資料是真是假。而若是發現所傳輸的資料是無用的，則馬上從網路中移除以節省能量消耗。 另外，無線感測網路通常是用來代替使用者監控整個環境，所以網路使用者常常會發出一些查詢訊息來索取感測節點所感測到的讀值。但是一旦中間節點被惡意者所控制，則雖然現有的密碼機制可以保證網路使用者不會收到遭到竄改的資料，但是被控制的中間節點卻可能持續地回報給使用者說目前網路中沒有所要求的讀值，而這將造成使用者一直無法拿到有效資料。因此，我們提出一個稱之為SQ的機制來保證網路使用者除了可以能拿到真資料之外，也還保證一定能拿到所有他該拿到的資料而不會有哪些資料遭到中間節點惡意移除。 最後，由於感測節點通常便宜而缺乏保護，因此惡意者其實有機會除了可以控制使用者的感測節點之外還可以複製出多個感測節點來破壞網路的功能。這種攻擊的特點是所有的被複製出來的感測節點裡面都有合法的金鑰，所以都可以被視為是一種合法的感測節點。因此，這種攻擊對網路的日常運作的危害相當大。在靜態網路當中，已經有一些方法可以來偵測這種節點複製攻擊。但是在動態網路當中卻遲遲沒有對應的防禦機制出現。因此我們提出了第一個能在動態網路當中偵測並移除複製節點的方法。 以上的方法都具有理論分析與數據模擬。另外，這些方法也都被實際實現在真正的感測節點上來證明其可行性。
並列摘要
We address three security issues in sensor networks in this thesis: key pre-distribution, hop-by-hop authentication, and secure multidimensional query. As a security primitive, key establishment plays the most crucial role in the design of the security mechanisms. Unfortunately, the resource limitation of sensor nodes poses a great challenge for designing an efficient and effective key establishment scheme for Wireless Sensor Networks (WSNs). In spite of the fact that many elegant and clever solutions have been proposed, no practical key establishment scheme has emerged. In this thesis, a emph{ConstrAined Random Perturbation based pairwise keY establishment} (CARPY) scheme and its variant, a CARPY+ scheme, for WSNs, are presented. Compared to all existing schemes which satisfy only some requirements in so-called emph{sensor-key criteria}, including 1) resilience to the adversary's intervention, 2) directed and guaranteed key establishment, 3) resilience to network configurations, 4) efficiency, and 5) resilience to dynamic node deployment, the proposed CARPY+ scheme meets all requirements. In particular, to the best of our knowledge, CARPY+ is the first non-interactive key establishment scheme with great resilience to a large number of node compromises designed for WSNs. We examine the CARPY and CARPY+ schemes from both the theoretical and experimental aspects. Our schemes have also been practically implemented on the TelosB compatible mote to evaluate the corresponding performance and overhead. Sensor networks are vulnerable to false data injection attack and path-based DoS (PDoS) attack. While conventional authentication schemes are insufficient for solving these security conflicts, an emph{en-route filtering} scheme, enabling each forwarding node to check the authenticity of the received message, acts as a defense against these two attacks. To construct an efficient en-route filtering scheme, this thesis first presents a Constrained Function based message Authentication (CFA) scheme, which can be thought of as a hash function directly supporting the en-route filtering functionality. Obviously, the crux of the scheme lies on the design of guaranteeing each sensor to have en-route filtering capability. Together with the emph{redundancy property} of sensor networks, which means that an event can be simultaneously observed by multiple sensor nodes, the devised CFA scheme is used to construct a CFA-based en-route filtering (CFAEF) scheme. In addition to the resilience against false data injection and PDoS attacks, CFAEF is inherently resilient against false endorsement-based DoS (FEDoS) attack. In contrast to most of the existing methods, which rely on complicated security associations among sensor nodes, our design, which directly exploits an en-route filtering hash function, appears to be novel. We examine the CFA and CFAEF schemes from both the theoretical and numerical aspects to demonstrate their efficiency and effectiveness. Moreover, prototype implementation on TelosB mote demonstrates the practicality of our proposed method. The two-tier architecture consisting of a small number of resource-abundant storage nodes in the upper tier and a large number of sensors in the lower tier could be promising for large scale sensor networks in terms of resource efficiency, network capacity, network management complexity, etc. In this architecture, each sensor having multiple sensing capabilities periodically forwards the multidimensional sensed data to the storage node, which responds to the queries, such as range query, top-$k$ query, and skyline query. Unfortunately, node compromises pose the great challenge of securing the data collection; the sensed data could be leaked to or could be manipulated by the compromised nodes. Furthermore, chunks of the sensed data could be dropped maliciously, resulting in an incomplete query result, which is the most difficult security breach. Here, we propose a simple yet effective hash tree-based framework, under which data confidentiality, query result authenticity, and query result completeness can be guaranteed simultaneously. In addition, the emph{subtree sampling} technique, which could be of independent interest to the other applications, is proposed to efficiently identify the compromised nodes. Last, analytical and extensive simulation studies are conducted to evaluate the performance and security of our methods. Prototype implementation on TelosB mote demonstrates the practicality of our proposed methods. Although defending against node replication attacks demands immediate attention, compared to the extensive exploration on the defense against node replication attacks in static networks, only a few solutions in mobile networks have been presented. Moreover, while most of the existing schemes in static networks rely on the witness-finding strategy, which cannot be applied to mobile networks, the velocity-exceeding strategy used in existing schemes in mobile networks incurs efficiency and security problems. Therefore, based on our devised challenge-and-response and encounter-number approaches, localized algorithms are proposed to resist node replication attacks in mobile sensor networks. The advantages of our proposed algorithms include (1) Localized Detection; (2) Efficiency and Effectiveness; (3) Network-Wide Synchronization Avoidance; (4) Network-Wide Revocation Avoidance.