“Set top box” (STB) is a device, which is connected to a television set at the consumer premises and which allows a consumer to view encrypted channels of her choice. The basic function of the set top box is to decrypt the channels and to convert the digital signals into analog mode for viewing on television sets. A smart card or viewing card is a part of set top box which allow only those channels to be viewed which are subscribed by the consumer and authorized by the service provider.