Subject: Re: Open issue: DPV relay

From: Peter Sylvester <[email-masked]>
Date: Wed, 10 Apr 2002 18:32:08 +0200 (MET DST)

> 
> I now understand why we disagree.
good. 

> 
> This service does *not* need to be provided by a CA. It can be provided by
> any service provider that the client is willing to trust. The case where it
> would be provided by a CA, would be a very specific case. In order to
> resolve disputes, the "proof" must directly come from the CAs. This means
> that CRLs as well as OCSP responses must be provided by CAs (or authorities
> empowered by the CAs). DPV responses would be of no value.

'directly come from' is not exactly defined.  

In OCSP, you have that either the response is signed by the same entity that 
signed the certificate or by an OCSP entity which has a certificate directly
signed by the CA in question with some extended key usage. 

To make the simple case, if a DPV response is signed directly by the CA
(or by an authorised responder), you have the same situation. 

(text deleted)

> > > > Since you haven't commented the next paragraph may I assume that
> > > > this is ok with you?
> > >
> > > > > > I think the general principle should be that there is one mode
> > > > > > that all information essential to understand what has contributed
> > > > > > to the final decision must be made available to the client.
> > > > > > (Not necessarily understood by the client).
> > >
> > > No. It is always necessary to provide a yes/no/unknown answer (or an error).
> > > It is optional to provide all the information essential to test again the
> > > certificate validity, should another party not simply trust the signed "yes"
> > > answer. It is certainly not necessary for the client to understand what has
> > > contributed to the final decision.
> > 
> > What is 'no':
> 
> It is *not* necessary for the client to gather all the information that has
> contributed to the final decision; i.e. relayed DPV responses, if any, are
> not needed.
> 
> > Where did I say that yes/no/unknown is NOT necessary? (is this the reason
> > for the no?) In the remainder you just rephrase what I have said.
> 
> With a *not*, which makes a big difference.
I think that there must be a language problem somewhere because I
fail to see what *not* you are referring, i.e. to see where we are
in disagreement.  I have not said that it is necessary for the client
to gather all information. I have said that the protocol must provide
a method to allow a client to ask and the server to respond with that
information. 

> In case of a dispute, testing again the certificate validity, means that
> certificates, CRLs and OCSP responses must be available. Anything else is
> useless.

I think that this may be the core of our disagreement. 

This is because you only accept that CA can create assertions about the
validity of their certificates using CRLs and OCSP. As soon as you would 
admit that some new protocol or service is provided that enhances and in 
particular replaces them, the statements obtained via that service are
necessary. 

I would like to know what you would have said 5 years ago when only
CRLs existed.

Peter

---

From: Denis Pinkas <[email-masked]>
Date: Wed, 10 Apr 2002 18:47:04 +0200

Peter,

 
 
> signed by the CA in question with some extended key usage.

True.
 
> (or by an authorised responder), you have the same situation.

No. A CA can only assert information about what it is directly responsible.
No CA is responsible for all the certifiactes from one path. An OCSP query
is for ONE certificate, while a DPV query involves a CHAIN of certificates.

There are no similarities.

> a method to allow a client to ask and the server to respond with that

Maybe, since we possibly interpreted diffrently "what has contributed to the
final decision".

 
> validity of their certificates using CRLs and OCSP. 

Correct.

> As soon as you would

> I would like to know what you would have said 5 years ago when only

Basicaly the chain must be verified and no element fom the chain must be
revoked. 

Five years ago this information was provided off-line, i.e. via CRLs. OCSP
allows to obtain the same information on-line. Between on-line and off-line
I currently see no other mechanism. 

The basic question is whether first-hand information and second-hand
information should be used. In case of a dispute, only first-hand
information is useful (certificates and revocation status information from
the CAs responsible for every certificate from the chain). DPV responses
(i.e. the signed "yes" answers) are useless, unless the plaintiff and the
defendant both trust the same DPV server.

Denis