OpenPGP smartcard, how vulnerable is it?

gnupg at gnupg at
Thu Aug 16 10:29:49 CEST 2012

Hash: SHA512

On 15/08/12 20:46, Alexandre Dulaunoy wrote:

> It's more than a theoretical attack, the Sykipot Malware is
> proxying access to the smartcard reader. And by so the attacker is
> able to use the functionality of the card without requiring to
> tamper the card itself.
> For a complete analysis of the malware:
>  I hope this helps.

Obviously, if malware is in control of your machine, one of the many
things it can do is talk to the smart card reader. It can't force you
to enter your card though, and it can't read the keys from the card
when it's inserted, and if you're using a hardware pin pad, it can't
intercept your pin either. It can attempt to initiate
decryption/signing, but it still requires the user to enter their pin,
so some sort of social engineering is also required. It could wait for
you to try to decrypt/sign something, and then send some alternative
data to sign/decrypt to the reader instead, but at least the user
would see that something went wrong, and that would only work for one
sign/decrypt operation.

So using a smartcard prevents an attacker from getting access to your
keys, and severely limits the amount of decryption/signing they can do
even if they completely own your machine. However, if they completely
own your machine, you're probably screwed anyway.

On the other hand, this is not what was originally asked. The question
is, can an attacker with physical access to the card, either use it,
or read the keys off it. And the answer is: With a lot of money, probably.

Personally, I think that remote attacks against my system are many
orders of magnitude more likely than physical attacks where an entity
with lots of money steals my card and reads the keys off it. So I'm
happy to put my keys on a smart card.

- -- 
Mike Cardwell
OpenPGP Key    35BC AF1D 3AA2 1F84 3DC3  B0CF 70A5 F512 0018 461F
XMPP OTR Key   8924 B06A 7917 AAF3 DBB1  BF1B 295C 3C78 3EF1 46B4


More information about the Gnupg-users mailing list