[pkix] OCSP Signing Certificate Key usage standards

[daniel bryan <[e-mail]>]

Hello,

I am looking for guidance/standards on deploying an OCSP service in
specific regards to the key management of the OCSP Signing certificate.

Suppose I have a service, and I want to provide certificate status on 20
different certificate authorities using a "CA Designated responder"
described in section 2.2 of RFC 6960. Technically I have a few options:

*Option #1:* Generate 20 Keys on my HSM, Create 20 PKCS 10s, Submit all 20
for Signing to each CA. Import the Signed Certificate into my OCSP service.

*Option #2:* Generate 1 Key on the HSM, Create 1 PKCS 10 with a generic CN,
Submit 1 CSR to all 20 CA's. The CA will override the CN value during
Signing to reference their CA name, Import all 20 Signed certificates into
my OCSP service.

Option #1 adds complexity to key management, could potentially have an
impact on signing speed. An advantage is that if a key is lost/compromised,
it would only involve troubling one CA instead of all.

Option #2 will greatly simplify key management, and I speculate it will
increase the signing speed potential of the HSM, being that it doesn't have
to determine which key to use from a pool of 20 keys.  Obviously the bad
side is, if we ever loose the key, I would have to get all 20 CAs to sign
another request. This is especially bad when the certs have the noCheck
extension.


Here are my 2 questions:

*Q1:* From a security perspective, is option #2 worth considering.
Simplification is a huge priority, but security is a must.

*Q2:* Does the IETF/cabforum/Any other authority provide guidance/standards
on key management in this situation that I can use to support/defend the
choice?

Thanks,

--Dan