SlackBuildsOrg/libraries/xml-security-c

The xml-security-c library is a C++ implementation of the XML Digital
Signature and Encryption specifications. The library makes use of the
Apache XML project's Xerces-C XML Parser and Xalan-C XSLT processor.
The latter is used for processingXPath and XSLT transforms.

xalan-c is an optional dependency (autodetected).