security check while consuming wcf service

See more:

ASP.NET

WCF

i want to make security while any other websit's consuming my wcf service

for ex:

am having 5 web sit's and 1 wcf service

website-1 --->access--> ok (permission granted to access) wcf
website-2 ---->access-- X (no permissions to access) wcf
website-3 --->access--> ok (permission granted to access) wcf
website-4 ---->access-- X (no permissions to access) wcf
website-5 ---->access-- X (no permissions to access) wcf

i hosted my web service on IIS (hosted in internet), here i wana give permission to access my web service to only my paid websit's(1,3) and i wana restrict other sits(unpaid or public) to consume my wcf service

by using some software we can know the webservice address link. by knowing this wcf service link we can add that service to our sit.. while adding it must hav to ask certificate prove that their are paid sit's or not


security check at client location.... when client having my wcf service link address and ready to consume my wcf service(adding service reference to their project) it must check client is paid user or public user.. if its paid user, add service reference "success full" or its public user means , adding service reference "declined due to security"

soo.. what i hav to do for this security process

thanks