Re: Default encryption for Message

[Daiki Ueno <ueno@gnu.org>]

Jens Lechtenboerger <jens.lechtenboerger@fsfe.org> writes:

> 5. Refactoring
> mml1991.el, mml2015.el, and mml-smime.el share code, forcing
> copy-and-paste on updates.

Unifying those code would be a good idea.

> With Ma Gnus v0.7, mml2015-epg-find-usable-key was rewritten with an
> incompatible list of arguments to use the new function
> mml2015-epg-check-sub-key, while mml1991-epg-find-usable-key
> remained unchanged.  Why actually?

I guess it's a left-over.

> To be honest I don’t understand the comment in
> mml2015-epg-find-usable-key about “Non e-mail user-id” with
> mml-signers and mml2015-encrypt-to-self.  In fact, I don’t
> understand mml2015-encrypt-to-self (which is not mentioned in the
> manual) at all.  If I set that to true I cannot send encrypted
> messages but receive the error: “Neither message sender nor
> mml2015-signers are set”

mml2015-encrypt-to-self requires that either mml2015-sign-with-sender or
mml2015-signers is set.  If the former variable is set, it looks up a
key by a sender's e-mail address.  Otherwise, it looks for keys listed
in mml2015-signers, which could be:

(setq mml2015-signers '("D7E69871" ...))

Here, "D7E69871" is a "Non e-mail user-id"[1].  Perhaps we could enable
mml2015-sign-with-sender by default, if mml2015-encrypt-to-self is set.

> I’m simply using encrypt-to and hidden-encrypt-to in gpg.conf.

This was the idea why epg.el dropped the options like
pgg-encrypt-to-self.  However, in the end we realized that the Gnus
usage of GPG needed more flexibility.  Some people use multiple keys
associated with a single e-mail address.  For example, I have several
keys associated with ueno@gnu.org for different purposes than encrypting
or signing mails, e.g. signing tarballs.

> In any case, I’d like to use a stable interface into epg and suggest
> to provide that in a new file, say mml-epg.el.  Then, we could move
> either mml2015-epg-find-usable-key or mml1991-epg-find-usable-key
> with the new name mml-epg-find-usable-keys into that file and use
> that in mml1991, mml2015, and mml-smime.  Actually, that function
> should have an additional Boolean argument specifying whether to
> return just one key or all of them.  Also, the functions named
> mml-epg-... in jl-encrypt.el could go into that file.

Agreed.

Footnotes: 
[1]  The acceptable patterns are described in: https://www.gnupg.org/documentation/manuals/gnupg/Specify-a-User-ID.html#Specify-a-User-ID