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Re: Namespace treatment for C14N

From: <dee3@us.ibm.com>
Date: Tue, 8 Jun 1999 15:17:22 -0400
To: w3c-ietf-xmldsig@w3.org
Message-ID: <8525678A.006DBA22.00@D51MTA10.pok.ibm.com>
URI's are not valid XML, in general. They can have multiple internal colons that
have nothing to do with the XML meaning of colon, etc.

I believe it does have the fix point property.  The URI still is present in the
output.  It is just that the prefix string is replaced by its hash.  If you
re-cannonicalize, you hash the same URI and get the same prefix.  Ditto for the
default namespace.

Donald

Donald E. Eastlake, 3rd
17 Skyline Drive, Hawthorne, NY 10532 USA
dee3@us.ibm.com   tel: 1-914-784-7913, fax: 1-914-784-3833

home: 65 Shindegan Hill Road, RR#1, Carmel, NY 10512 USA
dee3@torque.pothole.com   tel: 1-914-276-2668



"Joseph M. Reagle Jr." <reagle@w3.org> on 06/08/99 02:34:31 PM

To:   Donald Eastlake/Hawthorne/IBM@IBMUS
cc:   w3c-ietf-xmldsig@w3.org
Subject:  Re: Namespace treatment for C14N





At 12:14 PM 6/8/99 -0400, dee3@us.ibm.com wrote:
 >It's the hash of the URI, not the hash of what the URI points to.

That's how I first read it and thought, "that doesn't abide by the 'fixed
point property.' " But I thought, why bother? So I reread the following
"expanded"

 > >2. Hex coding of MD5 of the Expanded URI is used as the new prefix.

to read fetch the resource for security; which still didn't abide by the
fixed point property.

A hash of a hash will still be a different hash regardless if the first was
generated from the URI string or it's resource.

So:
1. Why bother with a hash of the URI string? Why not use the URI?
2. Is it worth losing "fixed point" because of it?

_________________________________________________________
Joseph Reagle Jr.
Policy Analyst      mailto:reagle@w3.org
XML-DSig Co-Chair   http://w3.org/People/Reagle/
Received on Tuesday, 8 June 1999 15:58:54 GMT

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