private key protection

Jerome Baum jerome at
Tue Oct 18 15:39:39 CEST 2011

> It doesn't prevent a trojan from signing something other than what you
> intended (if it's your master key on card, even another key or a new
> sub-key) but whether this is a problem depends on your threat model.

I should mention that the current OpenPGP card spec doesn't let the card
know whether it's signing a key or signing data. So there's no way to
prevent this attack other than not keeping your master-key on card.

I prefer keeping the master-key encrypted thrice and printed out in a
vault, surrounded 25x8 by guards authorized to use lethal force.

But seriously, I keep the master-key encrypted/printed and store it in
my safe deposit box. The sub-key goes on the card. Trojan issue is a
much smaller issue then, as the card includes a signature counter. I
also keep a backup of the encryption key in case the card breaks. That's
probably a good idea.

PGP: A0E4 B2D4 94E6 20EE 85BA E45B 63E4 2BD8 C58C 753A
PGP: 2C23 EBFF DF1A 840D 2351 F5F5 F25B A03F 2152 36DA

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