One embodiment of the present invention provides a system that uses a portable security token to facilitate public key certification for a target device in a network. During system operation, the portable security token is located in close physical proximity to the target device to allow the portable security token to communicate with the target device through a location-limited communication channel. During this communication, the portable security token receives an authenticator for the target device, and forms a ticket by digitally signing the authenticator with a key previously agreed upon by the portable security token and a certification authority (CA). Next, the portable security token sends the ticket to the target device, whereby the target device can subsequently present the ticket to the CA to prove that the target device is authorized to receive a credential from the CA.