Registration of algorithms in Apache Xml Security

[Fabio]

Hy,
I am using Apache Xml Security in an application of digital signature
and I need to customize only the function that performs the signature
because I want to perform the hash with Bouncy Castle and the
signature on a PKCS#11 smart card.
The question is this: have I to create a provider that overrides the
function of signature and then register it on config.xml, or is there
the possibility to register only my function that performs the
signature in my desired way despite of registering the entire custom
provider?

Thanks in advance.