How did you get here? PHY-layer path signatures

Physical layer techniques enable new security paradigms in wireless networks, such as node authentication based on channel characteristics. However, current approaches are often limited to one-hop scenarios. We investigate how the aforementioned authentication schemes can be extended to the multihop case. In particular, we design mechanisms to provide path signatures, which allow destination nodes to verify the path followed by packets in the network. This enables, for instance, detection of packets not being forwarded along the intended route directly at the physical layer and without the need for per-packet cryptographic schemes. We propose multiple approaches based on the accumulative effect of link CSI along multihop routes. We implement and evaluate them on a software-defined radio testbed. Our preliminary results show that we can successfully identify unauthorized nodes participating in the forwarding of packets up to a path length of six hops.