Security challenges in seamless mobility: how to "handover" the keys?

In this paper, we discuss key management challenges for seamless handovers across heterogeneous wireless networks. We focus on utilizing existing keying material from previous access authentications to expedite network entry. For a seamless handover, keys must be available at the target network at the time of the handover. Currently, industry is still exploring possible ways to handle keys for mobility. This paper identifies the challenges of secure derivation and timely distribution of such keys. We discuss solutions for intra- and inter-technology handovers within the same network and between networks with roaming agreements. The presented solutions include different types of handover key hierarchies and key distribution protocols. In addition, we analyze the tradeoffs between security and performance in the discussed solutions.