GnuPG and RSA/IDEA extensions

Rich Wales richw at
Tue Feb 16 10:13:20 CET 1999

Earlier, I wrote:

	RW > or else (2) an RSA extension for GnuPG using RSAREF

Werner Koch replied:

	WK > But have a look at the GPL and grep for "patent".

Would it be a violation of the GPL to have an RSA extension which con-
tained _only_ the required interface to the RSAREF library, so that the
user would have to obtain the RSAREF code separately (and agree to its
odious patent restrictions) in order to use it?

I'm definitely _not_ proposing to integrate RSAREF into GnuPG itself.
Apologies if I gave anyone that idea in my earlier message.

	RW > gpg: NOTE: cipher algorithm 1 not found in preferences
	RW > Is there anything I can do to get rid of this diagnostic?

	WK > OpenPGP requires such a warning.

But section 12.4 of RFC 2440 (third paragraph) says RSA may be supported
for backward compatibility, and that this constitutes an exception to
the other "MUST" rules.

This would seem (to me) to override the "MUST" rule requiring the above
warning about IDEA not being an explicit preference on an old RSA key.

	RW > when I do "gpg --edit-key" on one of my RSA keys,
	RW > and then give the "pref" (list preferences) command,
	RW > no preference info is shown.

	WK > Currently there is no menu to edit the preferences
	WK > and I'm not sure whether such a menu makes sense at
	WK > all (at least for the cryptographic algorithms).

For the "backward compatibility" support of old RSA keys, I agree -- as
long as it is also agreed that section 12.4 of the RFC relieves us of
the mandate to issue warnings when such keys are used for decryption.

As far as newer keys are concerned, though, it seems to me that GnuPG
really should provide a way to specify non-standard preferences.  Note
the last paragraph of section of the RFC:  "Implementations
SHOULD implement 'preferences'."

	RW > the list of "supported algorithms" I get with "gpg -h"
	RW > does not include RSA or IDEA.  Is this simply normal,
	RW > given that the RSA and IDEA code is being loaded from
	RW > extensions rather than being built in?

	WK > Kind of bug in --help - try "gpg --version"

OK.  Is it feasible to fix this bug?

Rich Wales         richw at

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