On Mon, 6 Apr 2015, Doug Montgomery wrote:

      Well, this is SMIME and it uses PKIX, so the proper way to express any
      kind of attributes is via EKU OIDs.

Part of the issue here is that we have large enterprise identity management 
systems that issue
credentials for security functions, but independent of application.  So while 
the EKU bits say
that a CERT is useful for encryption, it does not say if that is for file 
encryption, disk
encryption, or email encryption.  

Thus the EKU bits may not be enough to understand if the domain in question 
supports/allows
encrypted email or not.

Do we need the PKIX/SMIME people to write a document to express these?
This really seems to be in their domain, and using the DNS to work
around not having the right EKUs seems wrong to me.

  DANE/SMIMEA offers the potential to clearly express / control key
usage per service and at the domain level.

The DANE working group sees regular invasions of other IETF areas
whenever that area feels the DNS is trespassing on their domain. I'd
prefer not to see another wave.

And additionally, I do think it matters that we leak key usage intent
into the DNS - especially in the current architecture of a few big
resolvers like google dns and opendns seeing many of the queries.

Enterprise identity management systems, business process, and the laws and 
policies that govern
them are the long pole in the tent here.  At least on the enterprise side, we 
are not talking
about an individual getting a $5 CERT or running ssh-keygen.   

i would expect the enterprise to have a lot more control on the EKU's in
the certificates they hand out to their employees than I would have
ordering my $5 certificate online from an SMIME CA.

Paul

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