user account in sharepoint

Question

I have a confusing question regarding customized claim provider. I have a customized claim provider in sharepoint. The trusted site provides a incoming claim type of http://schemas.xmlsoap.org/ws/2005/05/identity/claims/nameidentifier with the value of the login ID and a http://schemas.xmlsoap.org/ws/2005/05/identity/claims/f3guid type with the value of a GUID. However login ID is not unique (reusable when it is deleted or inactivated) but GUID is. In my sharepoint site, how do I add a user from claim provider with GUID as an identifier instead of login ID?

Thank you for any help.