From their website: Your data is encrypted on-the-fly before leaving your browser. Passpack uses the AES-256 encryption algorithm...only you can decrypt it wit

From their website: Your data is encrypted on-the-fly before leaving your browser. Passpack uses the AES-256 encryption algorithm...only you can decrypt it with your secret Packing Key. If the technology works as they say, it is secure. Now the problem becomes how to verify whether it works as they say. It is almost impossible to verify claims like these. Theoretically, they can read your password anytime they want just by modifying the JavaScript (or whatever they are using ) and you will never know. Personally I would not trust them with my really passwords.