Abstract: An authentication system for authenticating the identity of a requester of access by an unauthorized service client to a secured resource. The system has a messaging gateway having a first set of instructions operable to receive from a requester purporting to be an authorized user of a secured resource a request for limited access to the secured resource by an unauthorized service client for a particular transaction; a server having a second set of instructions operable to determine a key string known to both the secured resource and the authorized user the requestor purports to be, the key string being adapted to provide a basis for authenticating the identity of the requester as the authorized account holder; and a service user interface having a third set of instructions embodied in a computer readable medium operable to receive transaction specific information input into the request by the unauthorized service client.

Abstract: 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 to the secured resource; means for generating and communicating to the purported authorized user a challenge string adapted to provide a basis for authenticating the identity of the requester; a means for receiving a response string corresponding to the challenge string; and a means for evaluating the response sting to authenticate the identity of the requestor.

Abstract: 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 generating and communicating to the purported authorized user a challenge string adapted to provide a basis for authenticating the identity of the requester; a means for receiving a response string corresponding to the challenge string; and a means for evaluating the response string to authenticate the identity of the requester.