Unfortunately (or fortunately), there is no "standard" for encryption. rinceWind has given you the docs for the "standard" crypt function but that's not really encryption but a one way hash function. demerphq has given you a nice listing of the CPAN crypt modules. Looking at the state of encryption right now, PGP is the defacto standard and there are many implementations of it (PGP, OpenPGP, GnuPG, others?). You can check out <toot>my tutorial</toot> on GnuPG which has a nice overview of encryption (IMHO) and plenty of links to additional information.

-derby