Secret Key and Private Key Capacities Over an Unauthenticated Public Channel

摘要

In this paper, the problem of key generation over an unauthenticated public channel in a network setup is considered. The considered model consists of four terminals: two legitimate terminals who need to share a key, a helper and an active adversary. The legitimate terminals and the helper are allowed to exchange messages over a public noiseless channel, to which the adversary has full access and may modify messages exchanged through this public channel. We investigate two types of keys: secret key (secure from the adversary only) and private key (secure from both the helper and the adversary). We characterize the relationship between the key rates in our model and the existing models with a passive adversary. We characterize conditions under which the generated key rates in this model are non-zero, and further provide an authentication scheme to show that key capacities, if are non-zero, are the same as those for the scenario with a passive adversary.