[justjohn]

public-key cryptography only solves computer-computer interactions. It does nothing to help me authenticate with my computer.

[dhx]

Physical security is the primary means of achieving human-computer authentication. Terminals in high-traffic locations, use of something along the lines of Common Access Card[1] and many other techniques can provide this level of authentication.

[1] https://en.wikipedia.org/wiki/Common_Access_Card