Re: Default encryption for Message

[Daiki Ueno <ueno@gnu.org>]

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

> I was interested in mml2015-encrypt-to-self and looked at its doc
> string.  Setting to t fails.  You explained that
> mml2015-sign-with-sender or mml2015-signers are necessary.
> However, I don’t want to sign and suggested gpg.conf/Bcc instead.

So, maybe improving the documentation of mml2015-encrypt-to-self would
be a good start?

> In your scenario, I see two choices, say concerning Alice with those
> three keys.
>
> (1) Friend Bob wants to send a message to Alice and is supposed to
> choose the correct key B (but neither A nor C).
>
> (2) Alice wants to send an encrypted message to colleague Charlie,
> and she wants to make sure that the message is encrypted to her key
> A (but neither B nor C) in addition to Charlie’s key.
>
> For (1), my code sets mm-encrypt-option to 'guided to enforce a
> manual choice so that Bob learns about the existence of those three
> public keys in the first place.  (Ted Zlatanov suggested to save
> that choice.)

I don't think this is a good idea.  I know some people ("security" fans)
like this kind of verbose behavior, but others don't even want to
remember key IDs and are prone to choose wrong keys.

There are criticisms about a related topic:
http://www.superlectures.com/guadec2013/more-secure-with-less-security

> For (2), I think that another variable would be necessary to
> customize what key to use for what recipient.  (Gnus could ask if it
> detects multiple encryption keys.)

No objection on that.

> I don’t see how either case is supported by mml2015, though.  What
> is your configuration?

It can be done by dynamically setting mml2015-signers upon sending.  For
some reason I use hooks (namely message-header-hook), but it can be done
more easily by using group parameters or BBDB.

(info "(gnus) Group Parameters")

> Besides, what is the intended meaning for signatures if
> mml2015-signers contains multiple keys?

This is certainly for the case when one wants to sign a message with
multiple keys.