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RE: Update to encrypting attributes and arbitrary data based on c onve rsations with SYMM group

From: Ed Simon <ed.simon@entrust.com>
Date: Fri, 9 Mar 2001 14:00:20 -0500
Message-ID: <A0E1DEC54ED42F4884DD9EEA00ACE37106D153@sottmxs08.entrust.com>
To: "'Cohen, Aaron M'" <aaron.m.cohen@intel.com>, "'xml-encryption@w3.org'" <xml-encryption@w3.org>
Thanks Aaron.
 
Everyone else, the only change to the example is that Aaron has added
"/EncryptionExtensions" to the SMIL namespace.
Ed

-----Original Message-----
From: Cohen, Aaron M [mailto:aaron.m.cohen@intel.com]
Sent: Friday, March 09, 2001 1:55 PM
To: 'Ed Simon'
Subject: RE: Update to encrypting attributes and arbitrary data based on c
onve rsations with SYMM group


Ed:
One change that I would make to this is that you cannot add things to the
smil20 namespace, you have to create a new namespace to contain the smil20
encryption stuff. So your example would look like this:
 
<video src="NotAuthorized.mpg" 
       alt="You need the proper authorizations to view the referenced
video." 
       enc:EncryptedDataManifest="./EncryptedDataManifest" 
       xmlns:enc=" http://www.w3.org/xml/encryption/
<http://www.w3.org/xml/encryption/> ..."> 

  <EncryptedDataManifest xmlns=" http://www.w3.org/xml/encryption/
<http://www.w3.org/xml/encryption/> ..."> 

    <EncryptedData Type="AttributeValue" Name="src"> 
      <CipherText URI="secret.enc"/> 
    </EncryptedData> 

    <smilenc:EncryptedSrc xmlns:smilenc=
<http://www.w3.org/2001/SMIL20/WD/>
http://www.w3.org/2001/SMIL20/WD/EncryptionExtensions> 
      <EncryptedData Type="video/mpeg" Name="secret.mpg"> 
        <CipherText URI="secret.mpg.enc"/> 
      </EncryptedData> 
    </smilenc:EncryptedSrc> 

    <EncryptedData Type="AttributeValue" Name="alt"> 
      <CipherText>AbCd...WxYz</CipherText> 
    </EncryptedData> 

  </EncryptedDataManifest> 

</video> 

-----Original Message-----
From: Ed Simon [mailto:ed.simon@entrust.com]
Sent: Friday, March 09, 2001 10:29 AM
To: 'xml-encryption@w3.org'
Cc: 'aaron.m.cohen@intel.com'
Subject: Update to encrypting attributes and arbitrary data based on conve
rsations with SYMM group




For the record, I'd like to make some slight modifications to the 
EncryptedDataManifest example.  These modifications are the result 
of discussions with the W3C SYMM group. 

In the example, we start with 

   <video src="secret.mpg" alt="Alien spaceship in hangar at Area 51."/> 

and we want to encrypt the MPEG and the value of the alt attribute. 
In the earlier resultant 
(see " http://lists.w3.org/Archives/Public/xml-encryption/2001Feb/0022.html
<http://lists.w3.org/Archives/Public/xml-encryption/2001Feb/0022.html> "), 
the src attribute remains the same and the alt attribute disappears. 
SYMM would prefer to have the option of eliminating the src attribute and 
keeping the alt attribute while modifying its value; the idea being that 
SMIL specifically states that while non-SMIL namespace stuff may appear in 
SMIL instances, there must be no alteration to the semantics of SMIL. 

So, keeping the SYMM requirements in mind, we get this result upon
encryption: 

<video src="NotAuthorized.mpg" 
       alt="You need the proper authorizations to view the referenced
video." 
       enc:EncryptedDataManifest="./EncryptedDataManifest" 
       xmlns:enc=" http://www.w3.org/xml/encryption/
<http://www.w3.org/xml/encryption/> ..."> 

  <EncryptedDataManifest xmlns=" http://www.w3.org/xml/encryption/
<http://www.w3.org/xml/encryption/> ..."> 

    <EncryptedData Type="AttributeValue" Name="src"> 
      <CipherText URI="secret.enc"/> 
    </EncryptedData> 

    <smil:EncryptedSrc xmlns:smil=" http://www.w3.org/2001/SMIL20/WD/
<http://www.w3.org/2001/SMIL20/WD/> "> 
      <EncryptedData Type="video/mpeg" Name="secret.mpg"> 
        <CipherText URI="secret.mpg.enc"/> 
      </EncryptedData> 
    </smil:EncryptedSrc> 

    <EncryptedData Type="AttributeValue" Name="alt"> 
      <CipherText>AbCd...WxYz</CipherText> 
    </EncryptedData> 

  </EncryptedDataManifest> 

</video> 

Note that the new model allows the <video> element's src and alt attributes 
to be used by non-encryption-aware SMIL-conformant process.  However, we 
still specify enough information so that an encryption-aware SMIL processor 
can display the "real" data. 

The <smil:EncryptedSrc> is a SMIL-defined element that the SMIL WG could 
define, if they wish, to indicate the encrypted video would normally be 
pointed to by the <video> element's src attribute.  The goal is for XML 
Encryption to define a reasonable degree of common syntax for encrypted 
data while NOT trying to predict how applications will want to process 
that data.  

As iterated in the recent XML Encryption meeting, I'm happy to put 
this topic on the backburner until we get more experience with XML 
Encryption implementations.  However, I just wanted to capture the results 
of the SYMM discussion for posterity. 

Ed 
Received on Friday, 9 March 2001 14:00:56 GMT

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