Securing network resources in opportunistic and delay-tolerant networks

In this thesis we investigate security problems of delay- and disruption-tolerant networks operating in challenged environments. In these settings, providing even basic services presents unique challenges due to environmental and infrastructure constraints. One challenge is to establish a private communication channel when peer security credentials are unknown or unobtainable. A second challenge is to secure personal resource contributions from abusive users when public access is uncontrolled.We investigate the above issues while focusing on two application scenarios: rural-area communication networks and ad-hoc personal device networks. First, we consider a method for establishing an initial security context using casual information that links users to well-known entities. Next, we investigate several secure resource management algorithms for controlling abusive users. Finally, we relax authentication requirements of our resource management algorithms to reduce overhead and support fragmentation. We evaluate proposed techniques through simulations and analysis.The main research contributions of this thesis are: 1. Novel Secure Initial Context Establishment Protocol: We suggest a simple technique for achieving secure communication by leveraging casual information to establish an initial security context. This knowledge links users to a more prominent entity whose security credentials are likely to be well-known. We evaluate the proposed technique by analyzing real-world social network data and simulating intra- and inter-region communication scenarios. 2. Resource Management Schemes: To prevent users from sending more personal data and forwarding less peer data we propose and experimentally evaluate a basic technique based on coarse-grained priority classes. User or node authentication can be the basis for constructing priority classes. We use simulations to show the effectiveness of the basic technique for handling abusive users. We also consider three extensions for handling trusted senders who may become abusive. 3. Impact of Fragmentation on Resource Management Schemes: Fragmentation improves message delivery ratios by optimizing limited contact. However, it negates the benefits of resource management when fragments cannot be authenticated. We extend our previous resource management schemes to support fragmentation and reassess their effectiveness. 4. Best-Effort Authentication: Best-effort relaxes full authentication assumptions required by intermediaries in our previous networking scenarios. We propose two techniques for implementing best-effort authentication and investigate their effectiveness in resource management algorithms. Simulations show that this approach is feasible for our target application scenario even when false positive rates are high. xvi...