disclosed is a method for providing a pay - tv service based on a session key . the method includes the steps of : selecting a desired pay event using a program guide displayed on a system of the subscriber and achieving a subscriber private key ; filling out a service application based on service information , signing the service application based on a digital signature scheme and encrypting the digital signed service application ; transmitting the encrypted service application to a broadcasting station and waiting a response of the broadcasting station ; receiving a session key and a subscription authority message from the broadcasting station , decrypting the session key and the subscription authority message and verifying the digital signature ; decrypting a channel key , achieving a control word , descrambling event audio / video streams and watching the event ; and if the event is terminated or the session key is not effective , stopping watching the event and deleting the session key .