Direct End-to-Middle Authentication in Cooperative Networks

Cooperative networks rely on user cooperation at the network layer to provide services, such as packet forwarding or shared access to other network resources like storage or Internet access. Examples of cooperative networks that build upon user contribution are ad-hoc networks, decentralized wireless mesh networks, micro-operator networks, wireless Internet access sharing networks or hybrids between these network types. However, while it enables new types of networks and services, the concept of cooperative network service provisioning also creates new attack possibilities for malicious and selfish users. For example, wireless multi-hop networks are particularly susceptible to attacks based on flooding and the interception of, tampering with, and forging of packets. Thus, reliable communication in such networks quintessentially depends on mechanisms to allow on-path devices, such as middleboxes, to verify the authenticity of network traffic and the identity of the communicating peers.Efficient standard authentication techniques for end-to-middle authentication typically assume the presence of shared keys within the network or rely on trusted third parties, such as on-line authentication servers. However, in cooperative scenarios, these approaches suffer from significant drawbacks in respect to functionality and efficiency. Moreover, the tight resource constraints of wireless routers and access points in cooperative scenarios make the use of more flexible but less efficient authentication techniques challenging. Hence, a careful selection of cryptographic components and the creation of new and flexible and efficient mechanisms is required to enable end-to-middle authentication in cooperative multi-hop networks.In this thesis, we address the problem of end-to-middle authentication on different levels of granularity, ranging from infrequent signaling events to rapid verification of high-bandwidth payload streams. The different security and performance requirements of signaling and payload traffic prevent the creation of a one-size-fits-all solution but requires the use of specialized approaches. We designed and analyzed three solutions that cover low-frequency signaling events as well as high-frequency payload protection.We first analyze and extend the Host Identity Protocol to enable secure publickey based end-to-middle authentication for signaling traffic. However, the use of CPU-intensive public-key verification prevents the use of this solution for verifying high-bandwidth payload streams. Consequently, our second solution focuses on more lightweight cryptographic components to provide end-to-middle authentication for payload. The Adaptive and Lightweight Protocol for Hop-By-hop Authentication, ALPHA, uses efficient hash functions and hash chains to enable rapid verification of the source and integrity of a payload packet. Finally, our third solution sacrifices end-to-middle integrity protection of the packet to further improve the verification performance. The family of Stream-based Per-packet One-time Token Schemes, SPOTS enables middleboxes to rapidly authenticate the source of a packet when the middlebox is agnostic to the contents of the forwarded packet. In combination, the three solution provide a flexible set of mechanisms that enables efficient end-tomiddle authentication for a wide range of scenarios within and beyond the setting of cooperative multi-hop networks.