Patent ID: 8605900
Filing Date: 2013-12-10
Classification: H04L,H04N

Abstract:
1. An audio-visual (AV) data receiving device comprising: an AV data receiving unit configured to receive, from an AV data transmission device, AV data encrypted and transmitted by the AV data transmission device according to a method for protecting copyright on a network; a decryption unit configured to decrypt the encrypted AV data; a relay device number checking unit configured to check whether the number of relay devices which relay transmission between the AV data transmission device and said AV data receiving device on the network is equal to or smaller than a predetermined value; a command transmission and receiving unit configured to transmit and receive a command to and from the AV data transmission device; a first authentication and key exchange unit configured to perform first authentication for checking the number of the relay devices by causing said command transmission and receiving unit to transmit and receive the command to and from the AV data transmission device, and is configured to exchange first key information with the AV data transmission device; a second authentication and key exchange unit configured to perform second authentication not involving checking of the number of the relay devices and exchange second key information, reciprocally with the AV data transmission device; and a key information switching unit configured to determine whether or not the first key information should be switched to the second key information, wherein, before said command transmission and receiving unit is caused to transmit and receive a command for restricting the number of the relay devices to and from the AV data transmission device, said key information switching unit is configured to cause said relay device number checking unit to check the number of the relay devices, and is configured to determine, when the number of the relay devices is larger than the predetermined value, that the first key information should be switched to the second key information, so that said command transmission and receiving unit is not caused to transmit and receive the command to and from the AV data transmission device, said second authentication and key exchange unit is configured to perform the second authentication and exchange the second key information, according to the determination by said key information switching unit, and said decryption unit is configured to decrypt the encrypted AV data, using the second key information obtained by said second authentication and key exchange unit.