Patent ID: 7685422

Claim:
An information processing apparatus which transmits encrypted contents for copyright protection to a communication apparatus via a network, comprising: an authentication/key exchange unit configured to perform authentication/key exchange processing with the communication apparatus through a first communication connection, and generate a first key shared with the communication apparatus; a round trip time measuring unit configured to send a round trip time measuring request including an encrypted value obtained by encrypting a measuring request identifier to the communication apparatus through the first communication connection, the measuring request identifier is updated every time the round trip time measuring request is sent and shared with the communication apparatus, to measure the round trip time indicating a time that a measuring request response for the request is received, and configured to check whether the measured round trip time is within a predetermined time, to check whether an encrypted value included in the measuring request response coincides with a value which is obtained by encrypting the measuring request identifier by using the first key, and to check whether a transmitting source of the round trip request response is the communication apparatus sharing the first key; an unique ID receiver which receives identification information unique to the communication apparatus encrypted by using the first key through the first communication connection when the round trip time measuring unit succeeds in the checking, and decrypts the unique identification information; an ID register unit configured to register the identification information unique to the communication apparatus decrypted by the unique ID receiver; a common key transmitter which encrypts a second key used for contents transmission by using the first key and sends the encrypted second key through the first communication connection when the round trip time measuring unit succeeds in the checking; an ID decryption unit configured to receive a contents sending request sent from the communication apparatus through a second communication connection and decrypt identification information unique to the communication apparatus encrypted by the first key included in the contents sending request by using the first key; an ID checking unit configured to check whether the unique identification information decrypted by the ID decryption unit is registered to the ID register unit; and a contents transmitter which encrypts the contents requested by the communication apparatus by using the second key and sends the encrypted contents to the communication apparatus through the second communication connection.