generate Signature subtree with dsig prefix

Hello!


What is the easiest way to create a Signature subtree with a specific 
prefix,
e.g., something like

<dsig:Signature xmlns:dsig="...">
 <dsig:SignedInfo>
 ...
</dsig:Signature>

?

I'm currently using xmlSecTmplSignatureCreate, but it doesn't seem to offer
this facility (judging from its list of parameters).  Instead, it always
generates

<Signature xmlns="...">
  <SignedInfo>
  ...
</Signature>


Thanks,


Alex