PGP: is there such a thing as a "signature only key?"

[Owen Blacker]

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Charles Lindsey, quoting Dave Bird:
> 
> >  It has been claimed to me there is such a thing as a "signature
> >  only key", and that the PGP program will (automatically) refuse
> >  to encrypt to it.
> 
> The feature was present even in PGP2.6.x. I.e., there is a bit in the key
> somewhere that tells whether it is signature only, and I presume PGP will
> refuse to encrypt to it in that case (I never actually tried, and for
> sure a competent hacker could soon bypass it). But I  don't think the
> options available to the ordinary user gave the ability to set that bit. 

It seems, fwiw, that what is happening is that the PGPsdk functionality
used by Turnpike is wrongly allowing the user to encrypt to a revoked
ElGamal encryption subkey.  I would assume (but don't know and haven't got
round to finding out yet) that the code is probably checking to see if the
whole-key is revoked, rather than just the subkey in question.

This thread is continuing on the PGP users list
<http://cryptorights.org/pgp-users/> rather than here as it's off topic for
this list.


O x
- -- 
Owen Blacker
Senior Software Developer / InfoSec Consultant    Wheel: Clerkenwell
See http://www.owens-place.org.uk/pgp.html -- more about my PGP keys
Sig  0xb48e805e | 0e31 ac2a 4ff2 62a0 89da  ddef 4223 99a6 b48e 805e

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