Abstract: 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.