Patent ID: 8289880

Claim:
A transmitting apparatus comprising: a processor configured to generate a check packet based on a counter value, which is incremented by a constant value; a communication interface configured to transmit said check packet to a receiving apparatus using User Datagram Protocol (UDP), and receive a response message to said check packet from said receiving apparatus, said response message including acknowledgement information based on said counter value included in said check packet, a shared secret key shared with said receiving apparatus, a hash and transmission information included in said check packet; a validating unit configured to validate said acknowledgement information based on said shared secret key; a timer configured to measure a response time of said response message from said receiving apparatus; a determining unit configured to determine whether said response time is less than a predetermined time; and a judging unit configured to judge whether content data transmitted to said receiving apparatus will be limited in usage right based on a result of said validation by said validating unit and a result of said determination by said determining unit, wherein the determining unit is further configured to determine whether or not the response message has been received and when it is determined that the response message has not yet been received, the determining unit determines whether an elapsed time measured by the timer from a time of sending the check packet exceeds the predetermined time, and the judging unit is further configured to limit the usage rights when it is determined that the response message has not yet been received and the elapsed time exceeds the predetermined time.