Patch: FAQ

Werner Koch wk at
Wed May 10 17:24:13 CEST 2000

On Wed, 10 May 2000, Klaus Singvogel wrote:

> use the (patented) idea algorithmen as cipher algorithmen too (and
> not 3des). Thats what I correct in the FAQ.

If you look at the PGP 2 data formats (e.g. rfc1991) you will notice
that there is indeed an algorithm indetifier and therefore it is
possible to replace IDEA by 3DES (or better CAST5 which uses the same
keysize and can be done very easily).

Please read the GPL before _distributing_ GnuPG together with a module
which implements a patented algorithm; doing so might vilolate the GPL.

> 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

Nope.  The cipher modules are the low level encryption.  The chaining
is done in cipher/cipher.c and the same for all symmetric ciphers.


Werner Koch				OpenPGP key 621CC013
OpenIT GmbH                             tel +49 211 239577-0
Birkenstr. 12                           email   wk at
D-40233 Duesseldorf           

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