Hi Peter,
that depends on the algorithm used for EXTERNAL AUTHENTICATE. Quite
typically CardOS uses a Retail-MAC, which is a single DES CBC with
IV='00.00.00.00.00.00.00.00' using the left key half applied to all
blocks, a decrypt with the right key half and a final encrypt with the
left key half applied on the final block (In short: single DES for n-1
blocks, triple DES for last block).
For the Smart Card Shell you could write
---8<------8<------8<------8<------8<------8<------8<------8<------8<---
//
// Authenticate against CardOS card
//
var card = new Card(_scsh3.reader);
var crypto = new Crypto();
var key = new Key();
key.setComponent(Key.DES,
new ByteString("01010101010101010101010101010101", HEX));
// Get challenge
var challenge = card.sendApdu(0x00, 0x84, 0x00, 0x00, 8, [0x9000]);
// Crypto.DES_MAC_EMV is a CBC generated Retail-MAC
var cipher = crypto.sign(key, Crypto.DES_MAC_EMV, challenge);
card.sendApdu(0x00, 0x82, 0x00, 0x81, cipher);
print("Card returns " + card.SW.toString(16) + " - " + card.SWMSG);
---8<------8<------8<------8<------8<------8<------8<------8<------8<---
However you will need to know the key value for the authentication key,
unless your system uses some way to derive the key from the PIN code
(Using SHA-1 for example). This is quite uncommon, so I would assume
that the PIN verification is done sometime before authentication takes
place (using VERIFY INS=20 APDU).
Andreas
Peter Koch schrieb:
> Hi all!
>
> I'm trying to do an EXTERNAL AUTHENTICATE against a CardOS 4.01 card.
>
> Requesting the challenge is easy. But how do I calculate the response?
>
> Here's an example that I captured with an USB-sniffer:
>
> APDU 1: 00840000 08, Response 584eb56f6d9f13c5 9000
> APDU 2: 00820081 08 cdddb92642a38d3b, Response 9000
>
> Does anybody know how response cdddb92642a38d3b was calculated
> from challenge 584eb56f6d9f13c5 using PIN 123456.
>
> I have already tried stuff like
>
> echo -en '\x58\x4e\xb5\x6f\x6d\x9f\x13\xc5' |\
> openssl enc -des-ede3-ofb -K 313233343536 -iv 0 |\
> od -tx1
>
> with different cyphers. Unfortunately I don't know what IV-value
> must be used. Any ideas?
>
> Peter
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|# #| Schülerweg 38
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