The password manager uses strong encryption using a key derived from the passphrase using
scrypt key strengthening algorithm. This ensures encryption is performed using a strong key
and that brute forcing the passphrase is time consuming.
If the user loses his passphrase no recovery is possible.
This greatly reduces the amount of encryption related code required. Thought
we still have todo our own key strenthening but this also is easier with Botan::PasswordHash.
