And how is that process, broadly speaking, Enrique?
you need first to create an original chain with an xlst
Dim ins As InputStream = File.OpenInput(File.DirApp & "\sat","cadenaoriginal_3_3.xslt")
'a lot of code here in between
Dim cadenaOriginal As String = strWriter.RunMethod("toString",Null)
after a long medling with java security features i sign it with the certificate, the key and the password
signer.RunMethod("update",Array(cadenaOriginal.GetBytes("UTF8")))
Dim selloBytes() As Byte = signer.RunMethod("sign",Null)
Dim sello As String = su.EncodeBase64(selloBytes)
comprobante.Sello = sello
Then with that info you sign the document with the certificate, keyfile and string.
Then you have you CFDI33 xml file signed.
i guess this is the same process for any xml signing feature, but i wouldnt know.