Patent ID: 7706534

Claim:
A method comprising: transmitting, from a receiving device, a purchase request including a requested period of access to an encrypted program or service; receiving a key stream containing a plurality of key stream messages (KSM) wherein the plurality of KSM is received at intervals corresponding to a key interval of time; determining, at the receiving device, a number of KSM decryption counts corresponding to the requested period of access and generated based on the key interval of time; decrypting a KSM received in the key stream; modifying, at the receiving device, the number of KSM decryption counts upon decrypting the KSM; determining, at the receiving device, whether the modified number of KSM decryption counts has reached a specified threshold; and in response to determining that the modified number of KSM decryption counts has reached the specified threshold, ending access to the program or service by the receiving device.