Hmmm -
Ok - well obviously the most secure password storage is to crypt the password or even MD5 it. The problem being that making it a 2 way process immediately adds a whole new level of insecurity to it meaning that passwords can more easily be retrieved and decrypted from your database.
If you really want to be able to decrypt a password (and I don't really see a reason for it tbh), then you have several options.
1, Do soemthing quick and simple like base64 encode the password. Simple and easy to do, but means that any one just briefly looking at your data won't be able to read the passwords directly without doing a bit more work.
2, Write your own simple hashing script. Something that will jumble the letters up a bit but which is reversible. Although, all someone needs to do here is get hold of your decrypting PHP script and copy that, or just run the function.
3, Use an industry 2 way encyption algorithm. I'm sure there must be PHP libs for Blowfish (or something along those lines) out there already, it will just take a bit of hunting. The only problem here being that you now have to keep your keys secure in order to decrypt the passwords, as soon as someone finds your key, you've lost the security.
Anyhow - hope this helps..
