On 8/28/18 2:25 PM, Viktor Dukhovni wrote:
> 
> 
>> On Aug 28, 2018, at 2:43 PM, Peter Saint-Andre <[email protected]> wrote:
>>
>> The MTA-STS work seems very similar to PKIX over Secure HTTP (POSH) as
>> defined in RFC 7711:
>>
>> https://www.rfc-editor.org/rfc/rfc7711.txt
>>
>> Were the authors aware of POSH and, if so, what was the rationale for
>> defining a different approach?
> 
> One important difference is that TLS in SMTP is opportunistic, so
> much of the complexity is signalling *whether* to use authenticated
> TLS, rather than how to do the authentication.

Agreed.

> Secondarily, key fingerprints are fragile, name-based indirection
> is more robust, at the cost of trusting the usual panoply of CAs.
> Policies that pin names rather than fingerprints are much more
> stable, especially because the customer publishes the same MX
> hosts in their DNS, so it is data they control.

Thanks for the clarification, Viktor!

Peter

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