You can do what apple does for disk encryption: * Encrypt the data with a key (let the user print it out if you like) * Encrypt the key with the password of t

You can do what apple does for disk encryption: * Encrypt the data with a key (let the user print it out if you like) * Encrypt the key with the password of the user (or multiple users!) * Store the encrypted-encrypted-key on your server. If a user wants to change their password, their old password decrypts the key, and the new password re-encrypts the key.