[caops-wg] OCSP section 4

[Olle Mulmo]

On Jun 3, 2005, at 01:30, Mike Helm wrote:

> I think it is hard to make one rite answer & don't have a strong 
> opinion on this,
> but why _wouldn't_ the static info (local CRL) be the usual first 
> test?  Isn't it
> always the cheapest test?  Since it should _never_ be better than the
> the OCSP check, checking it last seems useless unless (and only unless)
> all the OCSP responses are timeouts or unknown.  So just do it first
> and then forget it (see above).

I'm not sure the gain outweighs the additional complexity. How many 
percent of the issued certificates are typically revoked? That's the 
maximum reduction of OCSP queries that you would get as a result. Plus, 
you have to watch out when encoding the logic: if you process the CRL 
first, the cert not being in the CRL should equal "unknown" and you 
should continue looking at other places; if you process the CRL last 
and the cert is not in the CRL, it should evaluate to "good".

IMO, it's only when you run a well-managed central service that you 
would really gain by query CRLs first, and assume that a non-entry 
means "good", as that requires proper conduct in regards to keeping the 
local CRL updated. The text in 4.2 should be enhanced to reflect this 
consideration.

We all know what disaster it is to have CRLs on client machines where 
we couldn't control such a conduct -- we shouldn't even try that again.

Also, one has to weigh in risk into the equation. For instance, a 
service may trust the locally cached CRL for HTTPS handshakes, but make 
an extra OCSP query before processing a transaction worth > €10,000. 
This is of course under the assumption that the OCSP query would return 
a state that is fresher (more fresh?) than what's available in the 
local CRL.

/Olle