+.PP
+Note that
+.BR catcrypt 's
+signatures do
+.I not
+provide `non-repudiation' in any useful way. This is deliberate: the
+purpose of signing is to convince the recipient of the sender's
+identity, rather than to allow the recipient to persuade anyone else.
+Indeed, given an encrypted and signed message, the recipient can
+straightforwardly construct a new message, apparently from the same
+sender, and whose signature still verifies, but with arbitrarily chosen
+content.