USB communication
=================

  * No command chaining, but extended APDU and extended Lc and Le

  * dwMaxCCIDMessageLength: 64


OpenPGP card protocol implementation
====================================

I try to follow "no clear password(s)" policy.
After key import, keystrings are also removed.
But because of this, we only support single key for this version.


How a private key is stored
===========================

KEYPTR
         ----> [   P   ][   Q   ][       N        ]
               <---encrypted----><---  plain  ---->

key_addr                       4-byte
additional_data_encrypted      16-byte
dek_encrypted_by_keystring_pw1 16-byte
dek_encrypted_by_keystring_rc  16-byte
dek_encrypted_by_keystring_pw3 16-byte

... decrypted to

[   P   ][   Q   ]
check   4-byte
random  4-byte
magic[] 8-byte