The use of ABFAB-based technologies requires that each user's device
is configured with the user's identities that they wish to use in
ABFAB transactions. This will require something on that device,
either built into the operating system or a standalone utility, that
will manage the user's identities and identity to service mappings.
Anyone designing that "something" will face the same set of
challenges. This document aims to document these challenges with the
aim of producing well-thought out UIs with some degree of