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RE: DSig & DOM & Databases

• From: Tony Coates <Tony.Coates@r...>
• To: xml-dev@l...
• Date: Wed, 04 Apr 2001 19:12:00 +0100

Aren't documents automatically canonicalised before the signature is generated?
If not, then why is the canonicalisation method included as part of the
signature information?

     Cheers,
          Tony.
========
Anthony B. Coates
Leader of XML Architecture & Design
Chief Technology Office
Reuters Plc, London.
tony.coates@r...
========

On 04/04/2001 10:54:08 Paul Spencer wrote:

>You need to differentiate between the meaning of the document and the
>lexical representation. The signature works at the lexical level, so
>everything is significant. This includes, for example, whether you use
>single or double quotes round attribute values. The simple answer is
>therefore that you cannot do *any* manipulation of the data. Even reading a
>document into a DOM where part of the document is signed, manipulating the
>unsigned part, then writing it back could invalidate the signature as the
>DOM processing will not preserve the lexical aspects of the document.
>
>That is the bad news. The good news is canonicalization (c14n). By putting
>the document into a standard canonicalized form before signing it, you can
>manipulate the document later and put it back into the same canonicalized
>form. Depending on what you have been doing to the document in the meantime,
>this should preserve the validity of the signature. The W3C has a c14n REC
>http://www.w3.org/TR/xml-c14n.


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