Abstract: A processing unit is connectable to a data communications network. The processing unit includes a device reader for a portable storage device. The portable storage device (e.g., a secure smart card) includes storage operable to supply a network identity for the processing unit and an access controller. The access controller is operable to prevent unauthorised writing to the storage. Before reading the network identity from the portable storage device, the processing device attempts a write to the storage of the portable storage device, and, only on determining that the write has failed, reads the supplied network identity. The processing unit is thereby able to check that the portable storage device is a valid secure data storage device and not a counterfeit portable storage device. If it is a genuine secure portable storage device, the write access will not be permitted, whereas if it is a non-secure portable storage device, there is a risk that it is a counterfeit.

Abstract: A portable storage device, for example a secure smart card, contains network identification information for a processing unit that is connectable to a data communications network, which processing unit includes a device reader for reading the portable storage device. The portable storage device includes storage and an access controller. The storage holds a network identity for the processing unit and at least one encryption key. The access controller is operable to control access to the storage by implementing key-key encryption. An embodiment of the invention thus provides a medium not only for storing a network identity for processing unit, but also for other secure information such as an encryption key associated therewith.