Re: [IETF-PKIX] OCSP Status Information on a Certificate

[SGalperin <SGalperin@xxxxxxx>]

In a message dated 98-04-17 12:31:04 EDT, you write:

>
>  At 08:48 AM 4/17/98 -0700, you wrote:
>  >And in the event a client receives {is revoked, not issued}, which
>  >dominates?  Similarly, {not revoked, not issued}.  I remain unconvinced
> this
>  >is no problem.
>
>  To the client, "not issued" is always more important than revoked or not
>  revoked. We can put that in the OCSP spec.
>
>  >As soon as OCSP clients are out there in any volume, there
>  >are those who will seek to determine the client's behavior in fringe
cases.
>
>  I fully agree. That's why I'm I don't think that issued/not issued should
>  be a MAY: I think it has to be a MUST. We can be sure that some clients
>  will blow the comparison unless they are always told whether or not the
>  cert was even issued.
>

Are we talking about fat OCSP client here ?
Does the OCSP client in this case have full certificate chain ?
Can we safely assume that fat OCSP client will need to verify signatures on
the chain first, validity and other X509v3 constraints and only then submit
OCSP request for status of every certificate in the chain ?

If this is so then, essentially, OCSP client is already in the possession of
the well-formed certificate signed by the (indirectly or directly) trusted CA
key. In these circumstances receiving an anwer "not issued" may only mean that
CA key is compromised and "unathorized" certificate has been signed. But if
someone has the CA key and can sign anything with it (including "unathorized"
certificates) then that someone can also make sure that "unathorized"
certificate has the same serial number as one of "authorized" and as long as
we only send serial number to identify a certificate in OCSP request the
substitution of the "authorized" cert with "unathorized" one will be
unnoticed. This makes "never issued" somewhat useless for fat OCSP clients.

Is this reasoning wrong ?

Also since CA archiving capacity is always finiteand we also talking about
allowing "historical" OCSP queries "never issued" will have to be replaced
with "info
unavailable" at least in some cases. This further redices the value of "never
issued" status.

--Slava Galperin