XML DSig (Digital Signature) is a standard published by the W3C that defines a common way of creating a signature in an XML document. This standard defines how to express the signature within an XML syntax, and how to determine what portions of the XML document are signed.
The Generic RSA engine is the default signing engine, and is used if no other engine type is specified in the signformat option. It automatically searches for any standard RSA certificates on the user's computer, which includes both Microsoft™ CryptoAPI and Netscape certificates.
You can use a number of different signatures engines.