/rot ther'teen/ [Usenet: from "rotate alphabet 13 places"],
v. The simple Caesar-cypher encryption that replaces each English letter with
the one 13 places forward or back along the alphabet, so that "The butler did
it!" becomes "Gur ohgyre qvq vg!" Most Usenet news reading and posting
programs include a rot13 feature. It is used to enclose the text in a sealed
wrapper that the reader must choose to open - e.g. for posting things that
might offend some readers, or spoilers. A major advantage of rot13 over rot(N)
for other N is that it is self-inverse, so the same code can be used for
encoding and decoding.