XKMS RegisterRequest -> PKCS10 Conversion

Hi,

I have a question about the following use-case. Does anyone has any
experiences or maybe done the same or has any ideas.

An XKMS-Client sends an XKRSS-RegisterRequest for certification of an
already created key-pair. This RegisterRequest is signed with the
private key with XMLSig at the Client. Now this Request needs to be
transformed to a PKCS10 Request at the XKMS-Server. But the PKCS10
Request must also be signed, but the XKMS-Server does not have the
private key.

Any Ideas?

* Maybe send a sign-Request to the XKMS-Client to sign the created PKCS10?
* Is there a way of sending PKCS10 Data inside XKMS?

thanx in advance for any help or suggestion

Stefan