The nWro Signing service is basically a SOAP web service on KPN Lokale Overheid's WebSign platform, combined with a client PKI government certificate hosted on a Hardware Security Module (HSM). This web service can be invoked via the Internet or KPN Lokale Overheid.

To invoke the web service, a PKI government certificate must be generated for the customer on the HSM and an account created on the WebSign platform. The web service must be invoked from an RO application. From there, a so-called Guide Form or Manifest, both in the form of an XML message, can be sent to the WebSign platform.

On the WebSign platform, the Guidance Form or Manifest is signed electronically using the PKIoverheid certificate of the respective client on the HSM. After signing, the XML file is sent back to the RO application.