Several questions about SmartCards

Jim Berland berland at
Mon May 28 11:46:54 CEST 2007

Hi everybody,

I tried to research most of my questions concerning the use of
smartcards, but I have a few things that I want to make sure.

_About smart cards:_

I understand that OpenPGP is a smart card specification that is not
very common among smart cards, so I should stick with the ones from
kernel concepts. It is similar with the card readers.

Is it correct, that this limitation changed with Gnupg2? I read that I
could use other cards now, but it wasn't clear enough (for me), which
ones those are. It's about PGP/MIME that is making it possible to use
other cards or something.

What would be the benefits of non-OpenPGP cards? Longer Keys? Different keys?

_About card readers:_

Did I understand it correctly, that card readers with a pin-pad don't
add extra security when used with GPG? I read that the benefit of the
pin-pad readers used with some applications is, that the pin never
reaches the computer and thus cannot be sniffed. Used with GPG this
doesn't apply though. Or is a pin-pad card reader used with GPG(2)
still a possible counter-measure to a keylogger attack?

Now assuming that pin-pad card readers don't add extra security, isn't
the number-only passphrase, that you would use with them, even riskier
than a simple card reader and a good passphrase?

Could I buy pin-pad readers, but ignore the pin-pad and use them like
simple card readers?

To make life not too hard for our people I would like to either have
long passphrase caching times with the gpg-agent (thinking of 4 hours)
or have them enter a shorter pin on the key-pad each time it's needed.
Which solution would you prefer?

I guess you are now going to ask me what the threat model is and I'm
afraid that I can't give a perfectly precise answer. Anyhow, the
computers are running MS Windows and are networked. I can definitely
see people opening email attachments to let a virus or whatever
strike. For that reason I liked the pin-pad readers, if they did what
they promise. The smart cards might be stored in a company safe or
actually taken home by everybody. I don't know yet. Storing the cards,
that are only to be used as an employee of the company, at the company
sounds reasonable to me and considering who has access to the safe a
short pin would (in my opinion) still be good enough. Please don't get
caught up trying to get this threat model perfectly right, but rather
concentrate on the other questions. I can figure this out by myself, I

_About other uses of the cards:_

To do something else with the smart cards other than using it for GPG
is not important, but might be very interesting. For example, would it
be possible to use it to authenticate for a Windows Remote Desktop

_At last, a possible technical problem:_

I read on the Microsoft website that it is possible to use smart cards
(readers) in a Remote Desktop session. Does this apply for the OpenPGP
card and an appropriate card reader? This is a requirement, because
all the work is done on a terminal server. The employee's computers
are complete computers and not thin-clients, although they don't do
more than a thin client would, I think.

Thank you very much for your help

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