Changing preferences

Kevin Hilton kevhilton at
Mon Sep 22 03:12:32 CEST 2008

> By the way... if I use setpref to set my encryption algorithms to
> AES256 and AES128, does it mean people won't be able to use, let's say,
> 3DES to send encrypted messages to, even if they are incapable of using
> AES? I mean... if I forget to add some algo, would I be making my key
> less compatible with other OpenPGP software?

The prefs associated with your key, is advertising to the sender what
you would prefer.  However the capabilities to decode an encrypted
version is really determined by your gpg version and what ciphers it
was associated with.  Unless you force an algorithm -- with the
cipher-algo preference, if your personal-preference list and the
preferences associated with the public key (showpref or pref) have no
matches in common (this is not a union of the sets), then 3DES is
chosen by default.  I believe all gnupg version since inception have
had the capablities to decode 3DES encrypted messages as dictated by
the OpenPGP RFC specifications.  (I could be wrong on this very last
statement).  The use of personal-cipher-preferences rather than
cipher-algo is preferred, since it prevents the problem of sending an
encrypted communication that the recipient can not decode.  If there
is a null union of the personal-cipher-preferences and the key
preferences, then 3DES is chosen.

Kevin Hilton

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