Re: [therightkey] Secure e-mail, and why it's not an intractable problem

[Olaf Kolkman <[e-mail]>]

On Feb 9, 2012, at 2:16 PM, Phillip Hallam-Baker wrote:

> For Alice and Bob there are many possible paths:
> 
> I very often start writing an email message on one machine and
> continue on another. In the course of a typical day I use a minimum of
> one PC, one Macbook, one iPhone and my work iPad. So for me it is
> actually quite usual for me to start writing an email on the Mac and
> continue on the PC. I typically read the messages on whichever one of
> the four machines is close at hand.
> 
> So the arity of the relationships is:
> 
> MUA -> MTA:  Many -> 1
> MTA -> MTA:  1 -> 1
> MTA -> MUA:  1-> Many
> 
> Now a good email setup should of course have multiple MTAs. But they
> should have a setup that makes them look like a single logical unit.
> There are many mail servers for example.com but only one logical mail
> service.
> 
> So now we see why security policy driven by MUA published security
> policy is going to fail: there is no consistency in the MUA loop. I
> read mail on four separate devices. They have no way to communicate
> between themselves to negotiate a common security policy and I
> certainly would not want them to.
> 
> Conclusion:
> 
> 1) Security policy is a property of MTAs and not MUAs and hence of
> domains and not accounts.


I am wading through the list trying to catch up... and something in the above makes me wonder.

You start of with Alice and Bob, describe a relation between machinery, and conclude that the security policy is a property of the machinery.

Why is the security policy not tied to Alice and Bob?


--Olaf


________________________________________________________ 

Olaf M. Kolkman                        NLnet Labs
http://www.nlnetlabs.nl/