An XML digital signature standard is applied to an XML document to sign it. The XML digital signature is an XML fragment with a specified schema that includes (a) data to describe how the signature should be calculated (e.g., digest methods, filters, and data sources) and (b) actual signature data (e.g., digests and signature values). The data describing how the signature should be calculated (i.e., the “group (a)” data) is placed inside an XML digital signature template, which is then used (e.g., by an API (application programming interface)) to create the actual digital signature containing the “group (b)” data.