Methods for the secure identification of the owner of a portable device by a service provider, wherein the portable device may be in communication with the service provider over a voice line such as a telephone line or the like, and the portable device does not require a personal computer. Furthermore, the methods provide for one-way, non-repudiable, non-trackable identification of the owner of a portable device, and for the arbitration of a disputed transaction between the owner of a portable device and a service provider.