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XML Schema base64Binary simple type

From: Gregor Karlinger <gregor.karlinger@iaik.at>
Date: Sat, 9 Jun 2001 12:18:31 +0200
To: "Joseph M. Reagle Jr." <reagle@w3.org>
Cc: "XMLSigWG" <w3c-ietf-xmldsig@w3.org>
Message-ID: <LBEPJAONIMDADHFHAEAOGEHECGAA.gregor.karlinger@iaik.at>

I think the current Schema definition at least of the 
DigestValueType leads to severe problems:

DigestValueType is derived by restriction from the XML Schema
simple type base64Binary. The *FIXED* value of the "whitespace"
facet is "collapse" for all atomic types other than string [1].

A value of "collapse" means that a validating parser normalizes
whitespaces in the string content of the DigestValue element. 

This behaviour could break the signature, if the signer produces
a digest value containing sequences of whitespaces, and the verifier
schema validates the signature.

Since the "collapse" value for the "whitespace" faced is *FIXED* we
cannot derive our DigestValueType from "base64Binary". Instead we
could derive the type by restriction from "string" since then we
are allowed to change the value of the "whitespace" facet to
"preserve" [1].

This issue is vital with respect to DigestValueType, but maybe it also
makes sence to change the definition of SignatureValueType, CryptoBinary,
X509SKI, ... since this elements are also likely to be covered by a 
signature, and then the same problem applies there.

[1] http://www.w3.org/TR/2001/REC-xmlschema-2-20010502/#rf-whiteSpace

Liebe Gruesse/Regards, 
DI Gregor Karlinger
Phone +43 316 873 5541
Institute for Applied Information Processing and Communications
Received on Saturday, 9 June 2001 06:18:39 UTC

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