Authenticate in SharePoint from ASMX web service 4.5

Hi,

I'm creating ASMX web service which stands between Windows service and SharePoint. Application pool of the web service is set to the user which is registered in SharePoint.

I'm trying to do some job under this user in SharePoint. Below is code:

var iden = System.Security.Principal.WindowsIdentity.GetCurrent();
var token = new SPUserToken(iden, new Uri(siteUrl));

SPUserToken creation fails with "This method only supports identities of type IClaimsIdentity" exception.

What am I doing wrong?