A system and method whereby the identity of a person, entity, device or the like attempting to gain access to a secured resource may be securely authenticated includes a means for receiving from a requester purporting to be an authorized user of a secured resource a request for access by an unauthorized user (such as, for example, a retail store, a service station, an on-line service provider or merchandiser, a healthcare provider, a medical insurer, an information consumer or the like) to the secured resource; a means for determining a key string adapted to provide a basis for authenticating the identity of the requester; a means for receiving an authentication credential associated with the request for access; and a means for evaluating the authentication credential to authenticate the identity of the requester.