RC-4 is the standard encrption logic, it has been while and pretty stable.
Here is the link for using RC4 encrption.
http://www.databasejournal.com/img/RC4_enhanced.sql
Cryptology is a huge subject.
Here is the link for how to have a secure system
http://www-theory.dcs.st-and.ac.uk/~...tml/node4.html