Analysis of Channel-Based User Authentication by Key-Less and Key-Based Approaches

User authentication (UA) supports the receiver in deciding whether a message comes from either the claimed transmitter or an impersonating attacker. Information-theoretically secure authentication can be implemented by using either a secret (symmetric key) shared between both the legitimate users or the transmission medium over which the message is transmitted [physical-layer authentication (PLA)]. We analyze these solutions when the physical-layer channel is the unique randomness source for either generating the key or performing PLA. For the symmetric-key-based UA approach, we resort to a secret key agreement. Moreover, we also consider an asymmetric-key-based UA based on the public-key (proven to be semantically secure), where the channel is used as an entropy source at one device only. We define the secure authentication rate at which the probability that the UA attack succeeds goes to zero as the number of independent and identically distributed variables describing how the channel goes to infinity. Both passive and active attacks are considered, and by numerical results, we compare the various UA schemes.