GPG Key Management Rant

2014 and it’s still annoyingly hard to find a reasonable GPG key management system for personal use… All I want is to keep the key material isolated from any Internet connected host, without requiring me to jump through major inconvenience every time I want to use the key.

An HSM/Smartcard of some sort is an obvious choice, but they all suck in their own ways:

FSFE smartcard – it’s a smartcard, requires a reader, which are generally not particular portable compared to a USB stick.
Yubikey Neo – restricted to 2048 bits, doesn’t allow imports of primary keys (only subkeys), so you either generate on device and have no backup, or maintain some off-device primary key with only subkeys on the Neo, negating the main benefits of it in the first place.
Smartcard HSM – similar problems to the Neo, plus not really supported by GPG well (needs 2.0 with specific supporting module version requirements).
Cryptostick – made by some Germans, sounds potentially great, but perpetually out of stock.

Which leaves basically only the “roll your own” dm-crypt+LUKS usb stick approach. It obviously works well, and is what I currently use, but it’s a bunch of effort to maintain, particularly if you decide, as I have, that the master key material can never touch a machine with a network connection. The implication is that you now need to keep an airgapped machine around, and maintain a set of subkeys that are OK for use on network connected machines to avoid going mad playing sneakernet for every package upload.

The ideal device would be a USB form factor, supporting import of 4096 bit keys, across all GPG capabilities, but with all crypto ops happening on-device, so the key material never leaves the stick once imported. Ideally also cheap enough (e.g. ~100ish currency units) that I can acquire two for redundancy.

As far as I can tell, such a device does not exist on this planet. It’s almost enough to make a man give up on Debian and go live a life of peace and solitude with the remaining 99.9% of the world who don’t know or care about this overly complicated mess of encryption we’ve wrought for ourselves.

end rant.

Comments

Comment by Andy Cater on 2014-07-12 21:13:09 +1200

You could do worse than contact Daniel Silverstone and whoever else made the Simtec entropy key. They should have the smarts to make a GPG enforcing key better than the Yubikey and it will come in tamper resistant housing 🙂

Comment by William Hay on 2014-07-13 01:12:22 +1200

The reader I use with my FSFE card(http://www.amazon.com/SCM-SCR3500-Smart-Card-Reader/dp/B00434WQVU) folds down to about the same size as a USB stick. The card itself fits in my wallet.

Comment by Ryan Nowakowski on 2014-07-13 01:55:57 +1200

The old Black Dog server on a USB stick might be an option.

Comment by Anonymous on 2014-07-13 02:59:20 +1200

What about the FSFE smartcard and a small-form-factor USB card reader?

Comment by Red7 on 2014-07-13 04:31:59 +1200

You can cut the FSFE smart card down to ID-000 size, and then use a USB-dongle sized reader, as described here: https://www.gnupg.org/howtos/card-howto/en/ch02s02.html#id251938

Comment by Simon Josefsson on 2014-07-13 21:52:32 +1200

The Neo supports primary key on card, as far as I know. Still 2048 bits though. I find it convenient to use sub keys on a neo: I would not want to revoke my master key if I lose my neo, but could easily revoke a set of sub keys if I lose my neo, and generate a new set of sub keys on another neo. This way I don’t disrupt the web of trust.

/Simon

Comment by G on 2014-07-14 03:15:30 +1200

What you describe as ideal exists: it’s an OpenPGP v2 smartcard (like the FSFE card) [1] with an ID000 form factor USB smartcard reader [2]. It works as advertised in Debian.

[1]: http://shop.kernelconcepts.de/product_info.php?cPath=1_26&products_id=42 [2]: http://shop.kernelconcepts.de/product_info.php?cPath=1_26&products_id=119

Comment by Tobias on 2014-07-14 23:31:02 +1200

Did you look at Gnuk (http://www.fsij.org/category/gnuk.html) and FST-01 (http://www.seeedstudio.com/wiki/FST-01) – This is compatible with GnuPG, but AFAIK it only support 2048-Bit keys – the reasoning being that longer keys make operations on the hardware awfully slow.

Or you could combine the Gemalto USB Shell Token (http://shop.kernelconcepts.de/product_info.php?cPath=1_26&products_id=119) with a OpenPGP smart card (e.g. http://shop.kernelconcepts.de/product_info.php?cPath=1_26&products_id=42 or the FSFE card, cut to size) and get another nice, small, hopefully tamper-resistant token.

Comment by G on 2014-07-18 21:18:06 +1200

I’m confused. I left a comment a few days ago which showed up on the site right away — now it’s gone. I hope you saw it; if it got lost, I’ll be happy to post it again.

Comment by Chris Boot on 2014-07-23 06:27:13 +1200

I use an OpenPGP smart card in a USB-stick sized reader (Gemalto ID Bridge K50). It works great with GnuPG 2.x and well enough with 1.x, and supports 4096-bit keys in all three slots simultaneously. It’s essentially the FSFE smartcard with a SIM cutout in a small reader.

You can usually get the smart cards from http://shop.kernelconcepts.de/product_info.php?cPath=1_26&products_id=42. I source the readers myself from elsewhere in the UK (http://smartware2u.com/products/73-gemalto-id-bridge-k50-shell-token.aspx).

HTH, Chris

Comment by Corsac on 2014-07-28 01:24:21 +1200

Use an OpenPGP card with SIM breakout (http://shop.kernelconcepts.de/product_info.php?cPath=1_26&products_id=42) and add an USB token (http://shop.kernelconcepts.de/product_info.php?cPath=1_26&products_id=119)

Comment by Matt Brown on 2014-08-11 01:14:42 +1200

Thanks for all the comments, and apologies for moderation delays… WordPress apparently stopped emailing me when comments are held for moderation so I only found the queue today 🙁

In any case, the OpenPGP smart card in ID000 form factor with a USB reader was also suggested to me on G+, and fits the bill perfectly. I’ve got the working nicely now.

Rant resolved 😉