A system for authenticating and authorizing a user to access services on a heterogenous computer network. The system includes at least one workstation and one authorization server connected to each other through a network. A user couples a personally protectable coprocessor (smart card) to the workstation by means of a bidirectional communications channel. The coprocessor is adapted to receive signals including first encrypted authentication information and to decrypt the first encrypted authentication information using a preselected first key. The coprocessor is further adapted to assemble and encrypt second authentication information using a preselected second key and to transmit the encrypted second encrypted authentication information to the workstation. The workstation then communicates the information onto the network whereby the user is authenticated to access the networked computer or service.