In this article I'm going to cover password hashing, a subject which is often poorly understood by newer developers. Recently I've been asked to look at several web applications which all had the same security issue - user profiles stored in a database with plain text passwords. Password hashing is a way of encrypting a password before it's stored so that if your database gets into the wrong hands, the damage is limited. Hashing is nothing new - it's been in use in Unix system password files since long before my time, and quite probably in other systems long before that. In this article I'll explain what a hash is, why you want to use them instead of storing real passwords in your applications, and give you some examples of how to implement password hashing in PHP and MySQL.
Password Hashing by James McGlinn