can algorithm preferences be changed?

Werner Koch wk at
Mon Sep 21 11:10:05 CEST 1998

Brian Warner <warner at> writes:

> Can the preferences be set or changed? (I assume they fundamentally can, but

Not yet, but I see that this is required.

> there's just no interface for it yet). Specifically, does a signature on my
> key include the preferences? If somebody signs my key, and then I change the
> preferences, does that signature become invalid? I want to upload my key but

Yes.  The preferences and the key expiration time are stored with the
self-signature and they are included in the hash so that you must
change (delete and add) your sef-signature.  I'll chnage the sign menu
to support this. 

> once there is a mechanism for it I intend to change the preferences to
> match GPG's capabilities (twofish, etc), so I don't want to start getting it

You should not put twofish into the preferences because it is an
experimental algorithm and the identifier may map to other algorithms
in other OpenPGP implementations.  There is no assigned number for
twofish yet.  Use "--cipher-algo twofish " to override the

> Is the lack of preferences likely to cause any weird behavior? Reading over
> the OpenPGP draft it looks like the sender will assume 3DES only, with ZIP
> compression.

Right.  (And I check whether gnupg really uses old ZIP if there is no
preference for RFC zip)


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