We consider a key distribution scheme for securing node-to-node communication in sensor networks. While most schemes in use
are based on random predistribution, we consider a system of dynamic pairwise keys based on design due to Ren, Tanmoy and
Zhou. We design and analyze a variation of this scheme, in which capturing a node does not lead to security threats for the
past communication.
Instead of bit-flipping, we use a cryptographic one-way function. While this immediately guarantees forward-security, it is
not clear whether the pseudorandom transformation of the keys does not lead to subtle security risks due to a specific distribution
of reachable keys, such as existence of small attractor subspaces. (This problem does not occur for the design of Ren, Tanmoy
and Zhou.) We show, in a rigorous, mathematical way, that this is not the case: after a small number of steps probability
distribution of keys leaves no room for potential attacks.
Keywords communication in sensor networks - key management - key distribution - forward security - directed random graphs