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Encryption SMIL and Streams

From: Joseph M. Reagle Jr. <reagle@w3.org>
Date: Fri, 01 Dec 2000 16:43:26 -0500
Message-Id: <4.3.2.7.2.20001201163528.01fedac8@rpcp.mit.edu>
To: www-smil@w3.org
Cc: Ed Simon <ed.simon@entrust.com>
On the XML Encryption list we've been discussion the requirement for 
streaming ciphers and whether that corresponds to requirements of streaming 
applications [1,2]. Is anyone in the SMIL community interested in the topic 
of using XML Encryption to support encrypting SMIL XML instances, as well as 
the resources they reference? If so, have a look at that thread and the 
draft requirements [3] and forward on any requirements/scenarios that you 
think are appropriate!

[1] http://lists.w3.org/Archives/Public/xml-encryption/2000Nov/0054.html
[2] http://lists.w3.org/Archives/Public/xml-encryption/2000Nov/0051.html
[3] http://www.w3.org/2000/11/15-xml-encryption-req.html

Forwarded Text ----
>From: Ed Simon <ed.simon@entrust.com>
>To: Public XML Encryption List <xml-encryption@w3.org>
>Date: Wed, 15 Nov 2000 17:07:18 -0500
>Subject: RE: Algorithm Selections
>
>The idea is that XML Encryption should support the encryption of arbitrary 
>data as well as XML elements and attributes.  For example,
>
><EncryptedDataManifest 
>xmlns="<http://www.example.org/xmlenc>http://www.example.org/xmlenc">
>
>   <EncryptedData Type="video/mpeg" Name="secret.mpg">
>     <DecryptionInfo>...</DecryptionInfo>
>     <CipherText 
> URI="<http://www.example.com/videos/secret.enc>http://www.example.com/videos/secret.enc"/> 
>
>   </EncryptedData>
>
>   <EncryptedData Type="text" Name="secret.txt">
>     <DecryptionInfo>...</DecryptionInfo>
>     <CipherText>JkE4T6S...</CipherText>
>   </EncryptedData>
>
></EncryptedDataManifest>
>
>In the above, secret.enc would be an encrypted MPEG video stream, and the 
><DecryptionInfo> would provide the info necessary for decrypting it.
>
>Now how would this work in SMIL, or indeed any XML where one wants to 
>encrypt linked data such as a GIF used by an XHTML file?  I haven't thought 
>about this thoroughly yet, but here's an initial idea.
>
>The plaintext SMIL file:
>
><smil>
>...
><video src="secret.mpg"/>
>...
></smil>
>
>And here's the SMIL file after the MPEG has been encrypted and stored in 
>"secret.enc" (and secret.mpg deleted):
>
><smil>
>...
><video src="secret.mpg" enc:EncryptedDataManifest="./EncryptedDataManifest" 
>xmlns:enc="<http://www.example.org/xmlenc>http://www.example.org/xmlenc">
>   <EncryptedDataManifest 
> xmlns="<http://www.example.org/xmlenc>http://www.example.org/xmlenc">
>     <EncryptedData Type="video/mpeg" Name="secret.mpg">
>       <DecryptionInfo>...</DecryptionInfo>
>       <CipherText 
> URI="<http://www.example.com/videos/secret.enc>http://www.example.com/videos/secret.enc"/> 
>
>     </EncryptedData>
>   </EncryptedDataManifest>
></video>
>...
></smil>
>
>When a SMIL app is processing the <video> element, it detects that there is 
>an EncryptedDataManifest attribute pointing to data that needs to be 
>decrypted.  Upon decrypting the contents of the manifest, it processes the 
><video> element in the normail way.  In the case of streaming, the 
>application may decrypt a block, stream it, decrypt the next block, stream 
>that, and so on.  (A general application-level processing rule for XML 
>Encryption is that upon detection of encrypted data, that data be 
>decrypted, if possible, before the application does any further processing.)
>
>To be honest, I need to learn more about SMIL and streaming technology 
>myself but hopefully I've expressed the scenario adequately here.
>
>Regards, Ed
>
>-----Original Message-----
>From: Joseph M. Reagle Jr. [<mailto:reagle@w3.org>mailto:reagle@w3.org]
>Sent: Wednesday, November 15, 2000 4:09 PM
>To: Ed Simon
>Cc: Public XML Encryption List
>Subject: RE: Algorithm Selections
>
>At 15:40 11/15/2000 -0500, Ed Simon wrote:
> >If XML Encryption is to be used for streaming media, as discussed in my
> >presentation at the work shop, then we will also need streaming ciphers.
>
>Ed,  at the workshop you mentioned things like SMIL which I'm somewhat
>unfamiliar with. I don't believe the SMIL instance is streamed, instead it's
>a discrete object that includes meta-data (synchronization) and
>references/invocations of streams [1]. Could you provide an example/scneario
>of how one would use XML Encryption with streaming ciphers?
>
>[1]
><http://www.w3.org/TR/2000/WD-smil20-20000921/extended-media-object.html#edef-ref>http://www.w3.org/TR/2000/WD-smil20-20000921/extended-media-object.html#edef-ref 
>
>
>__
>Joseph Reagle Jr.
>W3C Policy Analyst                <mailto:reagle@w3.org>mailto:reagle@w3.org
>IETF/W3C XML-Signature 
>Co-Chair   <http://www.w3.org/People/Reagle/>http://www.w3.org/People/Reagle/
End Forwarded Text ----

__
Joseph Reagle Jr.
W3C Policy Analyst                mailto:reagle@w3.org
IETF/W3C XML-Signature Co-Chair   http://www.w3.org/People/Reagle/
Received on Friday, 1 December 2000 16:43:34 UTC

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