XML namespace
XML Signature
Digital signatures embedded in the XML they sign. The namespace behind SAML assertions, signed SOAP messages and e-invoicing mandates.
xmlns:ds="http://www.w3.org/2000/09/xmldsig#"XML Signature signs a document from inside it: <ds:Signature> holds the digest, the algorithms and usually the signing certificate, and sits within the very document whose contents it covers.
That is why canonicalisation matters so much here. Two byte-different documents can be the same XML — attribute order, namespace declarations and whitespace all vary freely — so the signature is computed over a canonical form (C14N) rather than the raw bytes. Reformat a signed document with a tool that does not preserve canonical form and the signature breaks while the document stays valid.
You will meet it in SAML single sign-on, in WS-Security SOAP headers, and in national e-invoicing schemes that require a signed invoice.
- URI
http://www.w3.org/2000/09/xmldsig#- Prefix
ds- Elements
SignatureSignedInfoSignatureValueKeyInfoReferenceDigestValue
Specification: XML Signature Syntax and Processing
Formats that use it
SAML 2.0
<Response>A SAML 2.0 response carrying status and one or more identity assertions, usually signed and transported through a browser binding.
SOAP envelope
<Envelope>The message envelope for SOAP web services — still the backbone of banking, logistics and telecom, with its version carried by the namespace URI.
XML Schema (XSD)
<schema>The dominant XML schema language: namespace-aware, richly typed, and itself written in XML — so schemas diff and version-track like the payloads they govern.
UBL Invoice
<Invoice>The OASIS invoice document behind Peppol and most European e-invoicing mandates, splitting its vocabulary across three namespaces you must all declare.
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