Fujitsu was a successful participant in the XMLDSIG interoperability testing, missing a few points relating to optional RetrievalMethod, XPointer, XPath, and XSLT features.
Its Java-based implementation supports three key stores: the Java Security API, Microsoft Crypto API (including smart card), and Fujitsu's security library. You can choose whether to include Fujistu's XSLT processor, required for XPath filtering. If it is not included, you can use the JAXP parser in place of Fujitsu's XML parser. The signature processor (xmldsig.jar) is 146 KB. The XML parser (xmlpro.jar) is about 300 KB and the XSLT processor (xmltrans.jar) is about 400 KB.
For current information on Fujitsu's XMLDSIG products, see