This is how you can check what root certificate to install:
Open Home menu and type in Personal. An icon will appear, as shown below. After clicking on the icon, Nexus Personal program will start.
Double-click on Electronic ID.
Open in a new window, double-click on Digital Signature, or Digital Signature-2 if you have a renewed digital certificate.
Check whether you have Halcom CA PO e-signature 1 or Halcom CA PO 3.