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Re: EncryptionMethod in XMLEnc and SignatureMethod in XMLDSig

From: Christian Geuer-Pollmann <geuer-pollmann@nue.et-inf.uni-siegen.de>
Date: Mon, 01 Apr 2002 23:37:34 +0200
To: aleksey@aleksey.com, xml-encryption@w3.org
Message-id: <911510.1017704253@pinkpanther>
--On Montag, 1. April 2002 12:01 -0800 Aleksey Sanin <aleksey@aleksey.com> 
wrote:

> Sorry for mistype, actually Imeant SignatureMethod in XMLDSig:
>
> A minor issue but probably it's worth to fix it: the EncryptionMethod
> in XMLEncryption and SignatureMethod in XMLDSig both have the same
> meaning: algorithm selection. However, EncryptionMethod is *optional*
> element and SignatureMethod is *required*. From my point of view it is
> inconsistent. Either both should be required or both should be optional.
> I would prefer the second (both optional) since application can have this
> information from the context.

Hi Aleksey,

from Schema point, you're right. But I think they have different security 
properties:

For digital signatures (non-repudiation), the signed want's to state that 
he made a statement and he want that the binding between his identity 
(Certificate) and the signed contents is non-ambiguous. So it wouldn't make 
sense to omit the ds:SignatureMethod because that would let space for 
discussions (which algorithm was used).

For encryption (confidentiality), there are people who like "security by 
obscurity" as an additional point in their encryption system. So making the 
xenc:EncryptionMethod REQUIRED would force people to expose information 
which they probably do not want to disclose.


Maybe this is one motivation for this decision. But from implementors point 
of view, it adds some complexity.


Regards,
Christian
Received on Monday, 1 April 2002 16:33:09 UTC

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