How do a password secure an app in OS X?

It's not a good idea - you don't really want to store your passwords like that. OSX comes with http://www.macworld.com/2004/10/secrets/workingmac/index.php built right in. This is exactly what it is designed for. More secure than anything you could jerry-rig with AddressBook.

Another correct approach would be to make sure the data files are readable by your user account only (this should be true by default, but I haven't checked), then keep your user account (and the root/administrator account) secure—don't share your password, no auto-login, require password when waking from sleep, etc.

You could put it in http://www.apple.com/macosx/features/filevault/, which uses AES-128 super-secure encryption would stop someone from running the app. Of course that does nothing to help you, since someone could just open the data file and read out your passwords. A much better plan would be to listen to unixrat and use Keychain.

http://www.waterfallsw.com/wallet/ looks like it might do what you want. I've never used it before, so I can't vouch for its quality -- I just saw it linked the other day.

If you've got something against Keychain, I'd recommend http://www.versiontracker.com/dyn/moreinfo/macosx/17864&vid=103645 for this, which has proved reliable for me over the last three years, is very simple to use and, from what I've read by folk who know more about this stuff than me, encrypts your passwords securely.

You already have password security: it's called your user account. Simply don't allow anyone else access to that account; create other accounts as needed.

trevyn, I disagree. If his computer is compromised, his passwords and other information are easily accessible. The same goes if someone breaks into his domicile and steals the computer or if he sends his computer in for repairs - his data would be easily accessible by anyone with physical access to the machine. Encrypt the data if it's not something you would share with a stranger.

I've been using http://www.versiontracker.com/dyn/moreinfo/macosx/11502 for a while, which works rather well for my needs. it can store all sorts of other useful info aside from just your logins and passwords, and does it in an encrypted file. It appears to be a free app too (though i think you can register it for some additional functionality) I don't know, I've never needed it.

If you don't mind paying $40, http://www.barebones.com/products/yojimbo/index.shtml is a fantastic information organizing tool that supports individual item encryption. I've just started using the demo and it's fantastic.