Re: [ietf-dkim] SSP sender expectations

Wietse,

One other thing about the different, DKIM is not really a "ECHO/PUBLIC" 
concept. Its more direct mail with a complexity of mailing list as well.
Its funny that you bring this up.  I don't know if others remember 
Planet Connect (http://www.planetc.com) but in the early 90s' it was one 
the first commercially viable satellite based broadcasting "Mail and 
File" distribution systems. It was one the first ways before PPP 
connectivity was broadly viable to offer high bandwidth distribution of 
both internet and fidonet data.
It broadcasted:

    Usenet newgroups
    Fidonet Echo Mail (MAIL BONE)
    Fidonet Echo File (FILE BONE)

I can't recall the subscription model, but its receiver box including 
some "key" concept that control the subscription process and what data 
is dechipered.  If I recall, it was only unidirectional as with all 
early satellite broadcasting system and who used a phone line for any 
feedback requirement.
At the user end, typically a Mail Hub with its own subscribers using 
UUCP/SLIP or FTP or FIDONET, it only collected the data of group 
interest, discarding the rest.  If a member subscribed to a newsgroup or 
fido echo, it included the item for the collection.
Now, it could it been used to send direct mail? or a mailing list 
broadcast using a DKIM data encryption system?
Well, on the creation side. I will need an outbound wire (SMTP) to the 
PC site who would broadcast it.  As part of the broadcast, it could 
encrypt the email with the subscriber PC key.
Putting aside security issues, it is theoretically possible for my 
receiver box will see this email packets and will automatically decrypt 
only those DKIM emails belonging only to this box.
In this case, the PC service will do all the DKIM validation and SSP 
checking before the PC subscriber encryption and broadcast takes place.
Of cause today, the encryption part is not required because the ISP site 
(SMTP receivers) will direct/hold mail for MUA subscriber pick up.  No 
broadcasting concept.
The SMTP receivers can do the DKIM/SSP checking and the end-users don't 
have to worry about it.
--
HLS


Hector Santos wrote:
> Wietse Venema wrote:
> > Perhaps an analogy from a different but familiar world will help.
> >
> > Consider DKIM or SSP as broadcast radio transmissions (or TV if
> > you must). The point is that it is a UNIDIRECTIONAL thing.  The
> > sender doesn't know if anyone is receiving the signal, and they
> > certainly can't force anyone to listen (or watch their TV program).
> >
> > Likewise, the sender of DKIM-enabled email doesn't know if the
> > receiver implements DKIM or SSP, and they certainly can't force
> > them to implement unenforceable statements that say "deny".
> >
> > DKIM and SSP have no more "enforcement" power than broadcast radio.
> > You don't know who "receives" the signal and you certainy can't
> > force them to do anything with it.
> >
> > With the DKIM and SSP broadcast model, you can define the format
> > of the signal and its meaning. That's all. If you want to control
> > the receiver and "deny" mail, then you need a fundamentally different
> > model.
> Yes Wietse.
>
> Thank you for highlighting the simple broadcaster/receiver model. It was 
> very appropiate.
> If I may fine tune (excuse the TV pun) the model....
>
> The new "technology" added to the electronic broadcast are with the new 
> XYZ (DKIM) markings in the bit, byte or packet streams (analog or digital).
> Only new compliant receiver boxes are capable of deciphering or making 
> any use of the XYZ markings in the stream or piggybacking on the stream.
> Now, what is the purpose of the new XYZ markings in the broadcast signals?
>
> That depends on who is doing it and way:
>
>  - Is this an Information based marking?
>  - Is this a new control-based marking?
>
> If we step aside a second using a real model, the TV satellite and cable 
> industry also faced both design questions.
>   - Informational - improved receivers gives you fancier menu, it
>                     addressed the ergonomics of the user experience.
>
>   - Controls - improved receivers allow the vendors to leverage new
>                subscription models, including helping them to secure
>                against pirating. This migh also include logic that
>                leverages new BI-DIRECTIONAL communications hardware.
>
> So who will want this?
>
> Well, the vendors (senders) will be tickled pink if they can get 
> everyone to purchase or license a new receiver box.  That way the vendor 
> profit margins are improved in the name of improving the quality of the 
> user experience/service. New feedback information will help in direct 
> marketing ideas.
> How about users?
>
> Well, I will venture to say only the users who don't want the additional 
> controls will be those with illegal subscriptions. So they will stay 
> away from any new receiver boxes if they don't have to.  But they might 
> desire the neat new GUI boxes because it now allows them to do all kinds 
> of other stuff, i.e. PVR.  Vendors know the power of marketing, so they 
> will entire these users and also migh offer some amnesty (Upgrade) program.
> So yes, indeed, the model is very appropriate for DKIM.
>
> However, the differences are these:
>
> The new XYZ/DKIM markings is a standard and not proprietary.  That means 
> other broadcasting vendors, including broadcasting sniffing pirates can 
> do the same thing and might be able to use to this to exploit 
> "something" about this new XYY/DKIM markings and know logic it is know 
> to allow or offer.
> So how we resolve this?
>
> Policy and authorization (SSP) concepts.
>
> Within the XYZ/DKIM broadcasting markings is a FEEDBACK bit that tells 
> the receiver how/where to double check the originality of the XYZ 
> packet.  This will require a BI-DIRECTIONAL concept and usually it back 
> to the original holder.
> Now my new receiver box is getting true signals from the vendor I am 
> paying money too and I don't have to worry about getting fraudulent 
> broadcasting that might try to do something harmful to my system or my 
> interrupt my watching (reading) entertainment.  I will get silly marque 
> messages on the TV screen trying to sell me something.
> Here's the irony:
>
>       Everyone is doing this in the telecommunications world
>       including broadcasting, DSL, Cable, Mobil market with
>       new bi-directional feedback capabilities now possible.
>
> Its about time we catch up with it in the EMAIL world too.

--
Sincerely

Hector Santos, CTO
http://www.santronics.com
http://santronics.blogspot.com

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