Re: Why are mail servers not also key servers?

[Paul Wouters <[e-mail]>]

On Thu, 20 Apr 2017, Jon wrote:

> Why are (E)SMTP servers not also key servers?

You will find a history of that discussion in the dane archives.

Basically, it is the equivalent to the domain's DNS servers acting as
key servers, except that:

- SMTP is often blocked cross-domain, eg by ISPs, hotspot operators, etc
- SMTP failure cannot be distinguished from SMTP attacks, whereas DNSSEC
   based published keys (eg OPENPGPKEY and SMIMEA) can be detected when
   blocked (DNSSEC returns bogus or indeterminate results)
- Using public DNS to publish keys allows for a level of indirection,
   making targeted attacks much harder to do.

> generate a key pair on registration, store those keys on the server (in
> an encrypted archive), and make the public key available. A little
> coding later and we've got key exchange and message confidentiality.

SMTP servers could be key servers without having the private key of
individuals?

> Some extra security can be had by giving mail servers their own keys
> with which they can sign exchanges (and remember each other). TLS can be
> used to as part of an initial key exchange if that is desired. Can
> we not extend smtp again to include the necessary key exchange commands?

I believe there was a draft that tried to do something like this.

Paul