[tor-dev] adding smartcard support to Tor

Razvan Dragomirescu razvan.dragomirescu at veri.fi
Sat Oct 17 18:19:38 UTC 2015

Thank you Ivan, I've taken a look but as far as I understand your project
only signs the HiddenService descriptors from an OpenPGP card. It still
requires each backend instance to have its own copy of the key (where it
can be read by an attacker). My goal is to have the HS private key
exclusively inside the smartcard and only sign/decrypt with it when needed
but never reveal it. An attacker should not be able to steal the key and
host his own HS at the same address - the address would be effectively tied
to the smartcard - whoever owns the smartcard can sign HS descriptors and
decrypt traffic with it, so he or she is the owner of the service.

Best regards,

Razvan Dragomirescu
Chief Technology Officer
Cayenne Graphics SRL

On Sat, Oct 17, 2015 at 4:43 AM, Ivan Markin <twim at riseup.net> wrote:

> Hello,
> Razvan Dragomirescu:
> > I am not sure if this has been discussed before or how hard it would be
> to
> > implement, but I'm looking for a way to integrate a smartcard with Tor -
> > essentially, I want to be able to host hidden service keys on the card.
> I'm
> > trying to bind the hidden service to a hardware component (the smartcard)
> > so that it can be securely hosted in a hostile environment as well as
> > impossible to clone/move without physical access to the smartcard.
> I'm not sure that this solution is 100% for your purposes. But recently
> I've added OpenPGP smartcard support to do exactly this into OnionBlance
> [1]+[2]. What it does is that it just signs a HS descriptor using
> OpenPGP SC (via 'Signature' or 'Authentication' key). [It's still a
> pretty dirty hack, there is no even any exception handling.] You can use
> it by installing "manager/front" service with your smartcard in it via
> OnionBalace and balancing to your actual HS. There is no any bandwidth
> limiting (see OnionBalance design). You can setup OB and an actual HS on
> the same machine for sure.
> > I have Tor running on the USBArmory by InversePath (
> > http://inversepath.com/usbarmory.html ) and have a microSD form factor
> card
> > made by Swissbit (
> >
> www.swissbit.com/products/security-products/overwiev/security-products-overview/
> > ) up and running on it. I am a JavaCard developer myself  and I have
> > developed embedded Linux firmwares before but I have never touched the
> Tor
> > source.
> There is a nice JavaC applet by Joeri [3]. It's the same applet that
> Yubikey is using. You can find well-written tutorial of producing your
> OpenPGP card at Subgraph [4].
> >
> > Is there anyone that is willing to take on a side project doing this?
> Would
> > it be just a matter of configuring OpenSSL to use the card (I haven't
> tried
> > that yet)?
> I'm not sure that it is worth to implement a card support in
> little-t-tor itself. As I said, all the logic is about HS descriptor
> signing. Python and other langs that provide readablity will provide
> security then.
> I think/hope so.
> [1] https://github.com/mark-in/onionbalance
> [2] https://github.com/mark-in/openpgpycard
> [3] http://sourceforge.net/projects/javacardopenpgp/
> [4] https://subgraph.com/sgos/documentation/smartcards/index.en.html
> Hope it helps.
> --
> Ivan Markin
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