In processing medical payments, the longstanding promise of computer networks has been their ability to convey insurance claims and other billing records, without need of the paperwork and documents that can be delayed in the mail or waylaid in some bureaucrat's file drawer. But for Peter Waegemann, that promise is a threat to insurance companies, hospitals, doctors and government agencies — unless the parties in an electronic transaction can be sure of one another's identities. Otherwise, he says, all parties could leave themselves open to fraud or legal liabilities in the event of an error or a network intruder.