Covert secret key generation

We investigate the possibility of covert and secret key generation over a discrete memoryless channel model with one way public discussion. Protocols are required to conceal not only the key but also whether a protocol is being implemented. For some models, we show that covert secret key generation is possible and characterize the covert secret key capacity in special cases; in particular, the covert secret key capacity is sometimes equal to the covert capacity of the channel, so that secrecy comes “for free.” Our main contribution is the analysis of a protocol that exploits the likelihood encoder to circumvent source coding with side information and privacy amplification.