Sounds like you're trying to do the XMLDSIG[1] verification part of the SAML[2] authentication protocol.
Most languages and platforms have a library mechanism to do this as it's not as simple as computing the hash (the content is hashed in a particular form for consistency, and there are a few specific transformations required).

What language and/or platform are you using?

[1] XMLDSIG : http://www.w3.org/TR/2008/REC-xmldsig-core-20080610/
[2] SAML 2.0 : https://www.oasis-open.org/committees/tc_home.php?wg_abbrev=security

On 12/28/2012 02:48 PM, Kevin Brown wrote:
> So, new job... I've been tasked with implementing SSO using SAML 1.1. The
> client provided a document that gives an example of the Response object
> that will be forwarded into our site when a user goes to login. I'm trying
> to figure out how to validate the XML that I'm given so that I don't
> blindly trust that the document hasn't been modified in some way or just
> faked.
> I have the keys (DigestValue and SignatureValue), but when I try to do a
> sha1 of the xml (minus all the parts in the <Signature></Signature>
> section, the hash doesn't match.
> Does anyone have any experience with this that they might be able to point
> me in the right direction?
> 
> 
> 
> 
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