Howto encrypt passwords in a database

If you are developing a password-protected web site, you have to make a decision about how to store user password information securely.

What is "secure," anyway? Realize that the data in your database is not safe. What if the password to the database is compromised? Then your entire user password database will be compromised as well. Even if you are quite certain of the security of your database, your users' passwords are still accessible to all administrators who work at the Web hosting company where your database is hosted. Scrambling the passwords using some home-brewed algorithm may add some obscurity but not true "security." Another approach would be to encrypt all passwords in your database using some industry-standard cipher, such as the Message-Digest Algorithm 5 (MD5).