Access to secure data through a portable computing system is provided only when a timer within the system is running. The timer is reset with the portable system connected to a base system, either directly, as by a cable, or indirectly, as through a telephone network. In an initialization process, the portable and base systems exchange data, such as public cryptographic keys, which are later used to confirm that the portable system is connected to the same base system. In one embodiment, the initialization process also includes storing a password transmitted from the portable system within the base system, with this password later being required within the reset process.