Smart card fragility?

Werner Koch wk at
Tue Sep 20 10:23:30 CEST 2005

On Mon, 19 Sep 2005 12:08:44 -0500, Alex Mauer said:

> It seems to me that there is a pretty big vulnerability of smart cards:
> that of the Admin PIN.  All a malicious card terminal would have to do
> is enter an invalid Admin PIN 3 times, and you've got a somewhat
> expensive and thoroughly ineffective paperweight.

Correct.  There is no way to prevent this. 

One could imagine a reader with keypad which reliable enforces the use
of the pinpad by catching all VERIFY commands and somehow is able tell
the user which PIN has been requested (requires knowledge of the smart
card application).  I don't know such a reader.

> The solution I see to this is, instead of treating a zeroed Admin pin
> failure counter as a flag denying access to the private key, instead
> treat it as a flag that tells the card to wipe all private keys.  When

Yes, this is possible.

> Is there some reason that this would not work, or would create a
> vulnerability?  It seems to me that this would be a major benefit in
> terms of cost of a card, since you could re-use cards as much as you

Actually card vendors won't see that as a benefit to them.  After all
there business is to sell cards.  For the user the real damage is not
the locked card but the loss of the keys which are far more valuable
than that piece plastic and silicon.

OTOH, I understand your concerns.  In particular when developing
applications a complete wipe out command would be a nice to have.  We
already discussed whether we can add such a thing as an optional
feature to the next release of the specification.



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