This paper presented a new scheme for the protection of
software against piracy. Its strength is based on diversity:each installed copy is unique. Updates are tailored to fit
one instance and one instance only. This way the ease with
which a useful additional copy can be created is diminished.
Furthermore, as illegitimate instances cannot be kept sound
and up to date unless a new line of defense is broken with
every critical update, this results in a dynamic nature of
defense.
We pointed out the improvements over previous approaches
and argued that it makes most forms of software piracy more
difficult in a realistic model under realistic assumptions.