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RE: URL-level trust (was: Re: XKMS)

From: Mike Just <Mike.Just@entrust.com>
Date: Thu, 29 Nov 2001 08:01:03 -0500
Message-ID: <9A4F653B0A375841AC75A8D17712B9C980F5BC@sottmxs04.entrust.com>
To: www-xkms-ws@w3c.org
I think Daniel raises a good point.  However, while this may be an ultimate
goal and usage of XKMS, there exist many installments today that have and
choose to rely on one or more root (CA) certificates and won't shift to
trusting XKMS servers overnight. In addition, users will likely not operate
under a single "policy" or "trust model". So the way you've described it, a
user may have to have many XKMS roots (I'm not saying this is bad, I'm just
drawing a potential conclusion from your statement).  I think the model of
fewer roots where each root can enforce several policies or models is also
likely.
 
Mike



-----Original Message-----
From: Daniel Ash [mailto:Daniel.Ash@identrus.com]
Sent: Wednesday, November 28, 2001 5:27 PM
To: 'Yassir Elley'; www-xkms-ws@w3c.org
Subject: RE: URL-level trust (was: Re: XKMS)



I like to think of XKISS (as opposed to PKIX) as a shift in the trust
relationship... from client-to-root to client-to-trust service.  The
"initially trusted public key", therefore, would be that of the trust
service rather than a root (of course the trust service may be a root... but
the point is that the client doesn't know or care).  The client only needs
to know about a particular service... not of a PKI, or PKIs from which
hundreds of different service may be derived.  Maybe certificate policies
will become service policies.  

The trust service is not necessarily a means to delegate path processing,
revocation checking, etc, it is a means to delegate trust decisions all
together.  The trust service/client relationship would therefore likely be
'tighter', or more specific than between a root and a client.  I think it
should be a goal of ours for the client to be entirely ignorant of roots or
any PKIX concepts altogether.       

From the trust providers' perspective I think we should focus on two trust
management technologies for use with XKMS (both of which the client should
be ignorant of): (1)PKIX, and (2)Something that doesn't exist yet... the
something that doesn't exist yet being the replacement for X509
certificates.  Certainly, with trust managed by the infrastructure only,
there will be no need to carry trust parameters around in a certificate.

-dan           


-----Original Message----- 
From: Yassir Elley [ mailto:yassir.elley@sun.com
<mailto:yassir.elley@sun.com> ] 
Sent: Wednesday, November 28, 2001 3:38 PM 
To: www-xkms-ws@w3c.org 
Subject: Re: URL-level trust (was: Re: XKMS) 

Hi Stephen, 

Since XKMS is meant to support a variety of underlying PKIs, 
I agree that it would be overly complex to allow the client to 
specify in the request every possible parameter for every possible 
underlying PKI. However, the concept of an initially trusted public key 
(trusted root) is probably common to every PKI. 

One suggestion is to allow the client to optionally pass the set of trusted 
roots as part of each request and have the service use 
those public keys (or some default if no trusted roots are passed in) 
when constructing chains. However, we will still need to additionally use
service URLs 
as trust selectors for other parameters which are specific to a particular
PKI 
(like X.509 certificate policies). 

Having said that, since we are going to need service URLs as 
trust selectors anyway, and for the sake of simplicity, it is probably
adequate to use 
service URLs for both purposes (trusted roots and PKI-specific parameters). 

-Yassir. 

Stephen Farrell wrote: 

> (Changed the subject again:-) 
> 
> Hi Yassir, 
> 
> Yes, the proposal is as you describe. Do you think that the "4th 
> root" scenario you presented is a real & common problem? (For 
> those applications likely to be xkms clients, that is.) 
> 
> This is definitely something we have to make sure we get concensus 
> on. 
> 
> Stephen. 
> 
> PS: The background to this for me, is that I'm really concerned that 
> as soon as we let "advanced" PKI concepts (e.g. n-th root CA, cert 
> policy qualifiers, PGP introducer, SPKI-tuple-thing) through the xkms 
> blood-brain barrier, then we're in danger or loosing the plot and 
> ending up with xkms being the union of all the bad/hard bits of 
> all current PKIs! An example might make this clearer: there'll be 
> an xkms nonRepudiation bit only over my dead body! :-) 
> 
> Yassir Elley wrote: 
> > 
> > I want to make sure I understand the proposal. 
> > 
> > If the underlying PKI is X.509/PKIX, I am particularly interested in 
> > how the X-KISS Validate service knows which trusted public keys 
> > and certificate policies to use when constructing a certificate chain 
> > on behalf of a certain client. 
> > 
> > I think the proposal I am hearing from members 
> > of the list is that a particular XKMS service point URL 
> > (e.g. http://xkms.xmltrustcenter.org/us_gov_bridge_ca_confidential
<http://xkms.xmltrustcenter.org/us_gov_bridge_ca_confidential> ) 
> > would be configured to use particular trusted public keys and
certificate 
> > policies (in this case, the bridge CA's public key and a certificate
policy 
> > of confidential) and would declare these trust semantics on some web
page. 
> > 
> > An XKMS client would have to be familiar with the trust semantics 
> > for a particular XKMS service (by going to the web pages of several 
> > XKMS services where the semantics are described) and the client would 
> > invoke the particular service that happened to use the trust anchors and

> > cert policies he wanted to use. 
> > 
> > So, if a client wanted to use three particular trusted roots, they would
have to find a service 
> > that would have those three trusted roots. If they wanted to use four
trusted roots, 
> > they would have to find a different service that used those four trusted
roots. If 
> > they wanted to use four trusted roots and wanted every certificate in
the chain 
> > to have a particular certificate policy, they would have to find a third
service that 
> > supported that permutation. 
> > 
> > Is my understanding of the proposal correct? 
> > 
> > -Yassir. 
> > 
> > Stephen Farrell wrote: 
> > 
> > > All, 
> > > 
> > > I'd tend to agree that the URL level "trust" model is the thing to go 
> > > with for xkms. 
> > > 
> > > Two further questions:- 
> > > 
> > > 1. Is there a specific issue with preventing replay of a reponse from
a 
> > > different service URL (but the same responder key etc.), or, is there
a 
> > > general issue with correlating requests and responses? That is, is the

> > > fix likely to be alongs the lines of "include the service URL in a
signed 
> > > response" or "include a random value in the request and that same
value 
> > > in the corresponding response" 
> > > 
> > > 2. Could anyone who disagrees with using service URLs as "trust
selectors" 
> > > or who thinks we *need* to specify a finer-granularity of something
(whether 
> > > in request or response) please speak up in the next couple of days? 
> > > 
> > > Stephen. 
> > > 
> > > Rich Salz wrote: 
> > > > 
> > > > > You wouldn't actually need to have a different WSDL description
per URL. 
> > > > 
> > > > No, you don't HAVE to have them; I was putting too much on the
"private" 
> > > > notation made in the current spec about the service URL. 
> > > > 
> > > > I'd expect someone who was providing an outsourced service would
want to 
> > > > keep each binding in a separate file, but that's just a guess. 
> > > > 
> > > > > Either suggested approach for handling multiple trust models would
work. 
> > > > > I think the real issue is whether the folks planning to build such

> > > > > services believe one of them makes their life simpler.  I tend to
favor 
> > > > > the URL model, but admit this view is based on fairly limited
thinking 
> > > > > about how I might want to deploy such a system. 
> > > > 
> > > > Same here. 
> > > > 
> > > > > I can't imagine clients trying to deal 
> > > > > dynamically with what trust models are supported by a given
service. 
> > > > > Going to web page to get info on supported trust models (like
current 
> > > > > CPS docs for CAs) seems adequate to me. 
> > > > 
> > > > Agreed. 
> > > >         /r$ 
> > > > -- 
> > > > Zolera Systems, Your Key to Online Integrity 
> > > > Securing Web services: XML, SOAP, Dig-sig, Encryption 
> > > > http://www.zolera.com <http://www.zolera.com>  
> > > 
> > > -- 
> > > ____________________________________________________________ 
> > > Stephen Farrell 
> > > Baltimore Technologies,   tel: (direct line) +353 1 881 6716 
> > > 39 Parkgate Street,                     fax: +353 1 881 7000 
> > > Dublin 8.               mailto:stephen.farrell@baltimore.ie
<mailto:stephen.farrell@baltimore.ie>  
> > > Ireland                            http://www.baltimore.com
<http://www.baltimore.com>  
> 
> -- 
> ____________________________________________________________ 
> Stephen Farrell 
> Baltimore Technologies,   tel: (direct line) +353 1 881 6716 
> 39 Parkgate Street,                     fax: +353 1 881 7000 
> Dublin 8.               mailto:stephen.farrell@baltimore.ie
<mailto:stephen.farrell@baltimore.ie>  
> Ireland                            http://www.baltimore.com
<http://www.baltimore.com>  
Received on Thursday, 29 November 2001 08:01:35 EST

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