One of crucial disadvantages of key predistribution schemes for ad hoc networks is that if devices A and B use a shared key K
to determine their session keys, then any adversarial device that holds K can impersonate A against B (or vice versa). Also, the
adversary can eavesdrop communication between A and B for the lifetime of the system.
We develop a dynamic scheme where a system provider periodically broadcasts random temporal keys (e.g. using GSM technology
or local broadcasting services) encrypted with keys from the main predistribution pool. Shared temporal keys (and not the
keys from the main pool) are used to establish session keys.
The trick is that the scheme broadcast is organized in such a way that with a high probability two devices share much more
temporal keys than the keys from the main pool of keys. Also, the shared temporal keys come not only from shared permanent
keys but predominantly from the permanent keys that are not shared by the devices. After each re-d...