Key proof of possession

[srdavidson]

The SMCWG should discuss options for a "secure process to establish that the entity controlling the email address also controls the public-private key pair."

This is mentioned on the Mozilla GitHub policy issues board - mozilla/pkipolicy#215
@CBonnell and @BenWilson-Mozilla

[RufusJWB]

Maybe we could combine this with device attestation.

[srdavidson]

New internet-draft "Use of Remote Attestation with Certification Signing Requests" would make this feasible
https://lamps-wg.github.io/csr-attestation/draft-ietf-lamps-csr-attestation.html

[defacto64]

This may seem obvious... but perhaps it isn't. Why do we need a proof-of-possession of the private key? What can the Subscriber do of evil if they don't possess the private key corresponding to the certificate they obtained from a CA ? If there is an answer, than I think it's better to spell it out.