Key Generation Using External Source Excitation: Capacity, Reliability, and Secrecy Exponent

We study the fundamental limits to secret key generation from an excited distributed source (EDS). In an EDS, a pair of terminals observe dependent sources of randomness excited by a pre-arranged signal. We first determine the secret key capacity for such systems with one-way public messaging. We then characterize a tradeoff between the secret key rate and exponential bounds on the probability of key agreement failure and on the secrecy of the key generated. We find that there is a fundamental tradeoff between reliability and secrecy.