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DateTime (DT) attribute in Reference

From: Amir Herzberg <AMIR@newgenpay.com>
Date: Thu, 5 Jul 2001 13:39:47 +0300
Message-ID: <078EE8822DCFD411AAA1000629D56ADC0B7D37@IMP01>
To: "Dsig (E-mail)" <w3c-ietf-xmldsig@w3.org>
Hi, 

I know this is late to propose any additions. However, while working on
protocol for secure transport of XML messages, I came upon the requirement
to refer from one message to another - specifying the time. Thinking more
about it I realized that many references to external data may need to
identify the specific time of the  reference. The reference currently
identifies the data by URI, but URIs specifically do _not_ identify the time
- they refer to a resource which may change over time. But when we hash and
sign a resource, of course we must identify the exact version of it, and
time is one of the best ways to do so.

My prefered solution is to add to Reference an optional element to contain
the time at which the reference was made, e.g. <Reference URI=`uri` DT='
2001-07-04T17:49:04T'>

(I like to call it DT, for Date & Time, simply because it's the convention
of IFX and OFX; but of course any other approriate attribute name e.g. Time
is fine by me)

Notice this is different from the time of computing the signature itself, as
a signature may often contain references to resources using their values at
previous time. I know that the issue of indicating the time of computing the
signature was addressed in the recommendation, and an application `... may
include such information in a SignatureProperties element within an Object
element.`. But this is the time of computing the (entire) signature, not the
time at which the contents of the Reference were `frozen` (and later hashed
to DigestValue). 

Best regards, 
Amir Herzberg
CTO, NewGenPay Inc.  
http://www.newgenpay.com/Amir/Herzberg.htm
SMS (urgent only!): _subject_ of email to aherzberg@walla.co.il
Received on Thursday, 5 July 2001 06:36:08 UTC

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