Subject: RE: OCSP identifiers

From: [email-masked] (Peter Gutmann)
Date: Sat, 18 Nov 2000 11:22:49 (NZDT)

Ambarish Malpani <[email-masked]> writes:

>c. You want to be able to have an OCSP responder be very highly available. We
>have been able to provide very highly available and distributed solutions to
>people trying to do PKI deployments based on OCSP in part because the data
>that had to be replicated was very simple.

You can't get much simpler than a list of cert hashes and a status value...
when I said I'd support pKCert what I was really supporting was hash( pKCert ),
since it's trivial to turn it into the hashed form I didn't really distinguish
between the two.  I'm certainly all in favour of the cert hash, but if people
insist on the unhashed pKCert I don't mind much either since all it involves is
a single hash operation by the server.

Probably the easiest option for everyone is to allow the pKCert and nothing
else and then let the server extract whatever it feels like (cert, hash(cert),
issuerAndSerialNumber, hash(issuer)+serialNumber, subjectKeyIdentifier, bit-
reversed DN with FFT of the keyUsage extension, or whatever else you want.  It
may make the requests a tiny bit larger, but it does have the great advantage
that it'll keep everyone happy.

Peter.

---

From: Rich Salz <[email-masked]>
Date: Fri, 17 Nov 2000 22:27:08 -0500

> You can't get much simpler than a list of cert hashes and a status value...

If you want the OCSP responder to be able to work *only* off CRL's (e.g.,
Valicert -- arguably the OCSP market leader), then cert hash isn't very
useful.

> Probably the easiest option for everyone is to allow the pKCert ...

In a previous message I said that during work at a previous employer we
determined that this violates a patent by Micali.  I held my nose and did some
searches this evening, and I believe I found it.  Claims 37ff of US Patent
5,717,757 filed Nov 96 and issued Feb 98:
	37. A method for providing authenticated information about certificates,
	comprising the steps of: 
	(a) receiving a request for information about a certificate including
	    a proof that the certificate is issued;
	(b) verifying that the proof is valid; and
	(c) in response to the proof being valid, providing the requested
	    information. 
	38. A method according to claim 37, wherein the proof includes providing
	an entire CA-authenticated certificate. 

enjoy.