Patch: FAQ

Klaus Singvogel ks at
Wed May 10 12:57:09 CEST 2000

On Tue, May 09, 2000 at 07:29:22PM +0200, Werner Koch wrote:
> On Tue, 9 May 2000, Klaus Singvogel wrote:
> > --- gnupg-1.0.1/doc/FAQ.orig    Sat Dec  4 12:29:59 1999
> > +++ gnupg-1.0.1/doc/FAQ Tue May  9 17:31:38 2000
> > @@ -123,7 +123,7 @@
> >      supported by GnuPG because it is patented, but if you have a modified
> >      version of PGP you can try this:
> >  
> > -       gpg --rfc1991 --cipher-algo 3des ...
> > +       gpg --rfc1991 --cipher-algo idea ...
> Watch out for the "...modified version of PGP .." - I assume that this
> is will be a 3DES one ;-).  The GNU project does not support patented
> algorithms and therefore you won't read IDEA in it :-).  Yes, I know
> that there are some countries where there is no valid patent on IDEA.

Sorry, but the FAQ speaks at this point of encryption for pgp 2.x
Yes, you have to have a modified version GnuPG, but you have to
use the (patented) idea algorithmen as cipher algorithmen too (and
not 3des). Thats what I correct in the FAQ.

I know, you can use 3des to make GnuPG encrypted messages readable
for pgp 5.x or 6.x users. But that's not the point the FAQ speaks
here of.

Another point: I build a modified version of GnuPG:
I built the idea/rsa modules, added the "load-extension idea"
"load-extension rsa" lines to my .gnupg/options, and check with
"strace" if the modules where used/opened (they were :-)
But still I can't encrypt a message with GnuPG 1.0.1 (rsa 1.10 and
idea 1.11) for a pgp-2.6.3ii user (myself). I get the error message
Error: Decrypted plaintext is corrupted.

If I look into the source-code I see that the error comes from the
idea decryption. I currently investigate this. My current assumption
is, that GnuPG does idea encryption in ECB mode, but pgp 2.x does
decryption in CBC mode. But I'm not sure, since I don't understand
the idea.c completly yet. I'll tell you more, if I find the error.

  .-.  | Klaus Singvogel
  oo|  | Caldera (Deutschland) GmbH, Naegelsbachstr. 49c, 91052 Erlangen
 /`'\  | email: ks at        internet:
(\_;/) | phone: ++49 9131 7192-300   fax: ++49 9131 7192-399 

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