Need to implement Digital signature

Hi,

We are trying to implement digital signature for the client.

As per the requirement ,Digitally signed document will be sent to the statutory bodies.

Please guide me how to implement digital signature in SAP with smart card stored private key ,since we already have 3 rd party tool to read digital signature through Card reader,certificate issued by NIC.

Please suggest pre-requisites and methodology for this.

Regards,

Nageswara Rao