In Latvian mythology, Austras Koks ("tree of the east" or "tree of the dawn") was a tree that grew from the start of Saules' (the sun's) daily journey across the sky. It is usually considered an oak.
... www.cl.cam.ac.uk/~rja14/tcpa-faq.html/ for a clear discussion of two prominent proposals.
Examples of existing "digital rights management" and "copy protection" ...