An apparatus and methods are disclosed for performing peer authentication without the assistance of a human “guard.” In accordance with the illustrative embodiments, a peer is selected from a non-empty set of candidates at authentication time based on one or more of the following dynamic properties: the current geo-location of the user to be authenticated; the current geo-locations of the candidates; the current time; the contents of one or more directories (e.g., a telephone directory, an organizational chart or directory, etc.), the contents of one or more call logs; and the candidates' schedules.