Re: [openpgp] AS2+OpenPGP protocol extension review request

[Stephen Farrell <[e-mail]>]

Hiya,

I just had a quick peek (will try read more later) but wondered
why PGP is a better primitive here than MLS? [1] (Or one of the
IM security schemes that motivated MLS, if dealing with a work-
in-progress like MLS is problematic.)

Ta,
S.

[1] https://tools.ietf.org/wg/mls/charters

On 12/02/2019 04:09, Ben McGinnes wrote:
> Hi all,
> 	For those of you either not subscribed to gnupg-devel or who
> may not have paid as much attention to it over the new year period;
> I've been working on a little thing which is ready for some form of
> peer review.
> 
> Essentially it's a design for extending the W3C's ActivityStream
> version 2.0 (AS2) and ActivityPub (AP) protocols for federated social
> networks (e.g. Mastodon and Pleroma) with OpenPGP in order to provide
> a host of features not inherently built into AS2 and AP.
> 
> The AS2 and AP designers considered it, but realised that they didn't
> have enough cryptographic knowledge to design it in a way that
> wouldn't shoot someone in the foot; and so they did the responsible
> thing in not making assumptions.  Instead leaving things open for that
> void to be filled later.
> 
> I found their work early last year and, upon reading the specs,
> realised that I was looking at a transport protocol.  Not only that,
> but all the most essential cryptographic functions which needed
> filling were already thoroughly addressed by another existing
> protocol: OpenPGP.
> 
> My post on this thing to the gnupg-devel mailing list is here:
> 
> https://lists.gnupg.org/pipermail/gnupg-devel/2019-January/034167.html
> 
> The W3C AS2 and AP specifications are here:
> 
> https://www.w3.org/TR/activitystreams-core/
> https://www.w3.org/TR/activitypub/
> 
> My extension proposal is the second draft and the first draft that has
> been posted publicly (the actual first draft was sent to the W3C AS2
> designers, a couple of GnuPG developers and a handful of others).  My
> design document is available here:
> 
> https://files.de.adversary.org/crypto/ac/index.html
> 
> The supplemental files (including public and private keys used in the
> examples) are here:
> 
> https://files.de.adversary.org/crypto/ac/supplemental.zip
> 
> Note: files.de.adversary.org is an AWS S3 bucket, so it will trigger
> an SSL cert error.  Ignore it or drop back to HTTP at your own
> preference.
> 
> Anyway, there are a number of people on this list in particular who I
> think could make sure that I haven't catastrophically cocked the whole
> thing up.  I don't think I have, but that's precisely when you should
> double-check to be sure.
> 
> So if as many of you as can spare the time could please weigh in and
> try to pick it apart; that'd be greatly appreciated.  It'll help make
> it stronger.  Those of you who've already been down the protocol
> design path are amongst those I'm particularly keen on checking this
> thing.
> 
> I do realise there are still matters to discuss and finalise with
> regards to transmission of keys; currently there are multiple options
> included and I expect some discussion around that.  There's also two
> versions of the Encrypted Note and I'm inclined to favour the second,
> slightly more complex version for a number of reasons; including
> working with other functions (like nesting a Signed Note inside it in
> a similar manner to signed & encrypted PGP/MIME emails).
> 
> 
> Regards,
> Ben
> 
> P.S.  I'm cross-posting this to the IETF OpenPGP WG mailing list on
>       the off chance that there might be subscribers to that who are
>       not also subscribed here or to gnupg-devel.  That may not be
>       very likely, but it is possible and so a copy there doesn't
>       hurt.  Apologies to those who will see it twice as result,
>       though.  Especially since you're the ones I'm most keen to want
>       reviewing this work.
> 
> 
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