How to Assign Symmetric Keys in a Network of Small Computers

We discuss several efficient schemes for assigning symmetric keys in a network of small computers (e. g. an ad-hoc or sensor network) such that any two adjacent computers in the network can communicate securely using the keys assigned to both of them. The schemes are efficient because they require that each computer be assigned O(log d) symmetric keys, where d is the network degree, instead of O(d) symmetric keys that one expects in a straightforward scheme