A compact, self-contained, personal key is disclosed. The personal key
comprises a USB-compliant interface releaseably coupleable to a host
processing device; a memory; and a processor. The processor provides the
host processing device conditional access to data storable in the memory
as well as the functionality required to manage files stored in the
personal key and for performing computations based on the data in the
files. In one embodiment, the personal key also comprises an integral
user input device and an integral user output device. The input and
output devices communicate with the processor by communication paths
which are independent from the USB-compliant interface, and thus allow
the user to communicate with the processor without manifesting any
private information external to the personal key.