Information processing apparatus and information processing method

An information processing apparatus which receives encrypted contents and key information attached to the contents transmitted from a communication apparatus connected via a network, comprising:

• authentication & key exchange unit which performs authentication & key exchange processing by using a given protocol with the communication apparatus and generates a first key shared with the communication apparatus;
• a contents receiver which receives encrypted contents obtained by encrypting the contents with a second key generated by using the first key and the key information, and the key information attached to the encrypted contents;
• a contents decryption unit which decrypts the encrypted contents by using the first key and the key information;
• and
• a contents confirmation request unit configured to instruct the communication apparatus to transmit or confirm the key information held by the communication apparatus, when the key information transmitted from the communication apparatus does not change in order agreed with the communication apparatus in advance.

An information processing apparatus which receives encrypted contents and key information attached to the contents transmitted from a communication apparatus connected via a network, comprising:

• authentication & key exchange unit which performs authentication & key exchange processing by using a given protocol with the communication apparatus and generates a first key shared with the communication apparatus;
• a contents receiver which receives encrypted contents obtained by encrypting the contents with a second key generated by using the first key and the key information, and the key information attached to the encrypted contents;
• a contents decryption unit which decrypts the encrypted contents by using the first key and the key information;
• and
• a contents confirmation request unit configured to instruct the communication apparatus to transmit or confirm the key information held by the communication apparatus, when the key information transmitted from the communication apparatus does not change in order agreed with the communication apparatus in advance.

An information processing apparatus which receives encrypted contents and key information attached to the contents transmitted from a communication apparatus connected via a network, comprising:

• authentication & key exchange unit which performs authentication & key exchange processing by using a given protocol with the communication apparatus and generates a first key shared with the communication apparatus;
• a contents receiver which receives encrypted contents obtained by encrypting the contents with a second key generated by using the first key and the key information, and the key information attached to the encrypted contents;
• a contents decryption unit which decrypts the encrypted contents by using the first key and the key information;
• and
• a contents confirmation request unit configured to instruct the communication apparatus to transmit or confirm the key information held by the communication apparatus, when a connection for contents transmission with the communication apparatus is once cut off and the connection with the communication apparatus is again established to begin the contents transmission.

An information processing apparatus which transmits encrypted contents to a communication apparatus connected via a network, comprising:

• an authentication & key exchange unit configured to perform authentication & key exchange processing by using a given protocol with the communication apparatus;
• a key generation unit configured to operate a given function by using the key information including a random number and the first key to generate a second key;
• an encryption unit configured to encrypt contents by using the second key;
• a contents transmitter which transmits the encrypted contents with the key information in plain text, to the communication apparatus;
• a key information updating unit configured to update the key information based on a given condition;
• a random number acquisition unit configured to acquire the random number included in a contents confirmation request transmitted from the communication apparatus;
• a key information acquisition unit which acquires the key information being currently used to encrypt the contents;
• and
• a contents confirmation response unit configured to transmit a message including the key information acquired by the key information acquisition unit and the random number acquired by the random number acquisition unit to the communication apparatus, as a contents confirmation response for the contents confirmation request.

An information processing method of transmitting encrypted contents via a network from a transmitter to a receiver, comprising:

• performing authentication & key exchange processing by using a given protocol between the transmitter and the receiver to generate a first key shared between the transmitter and the receiver,
• wherein the transmitter encrypts the contents based on a second key generated by a given function by using key information including the generated random number and the first key, and transmits the encrypted contents with the key information in plain text, to the receiver;
• the receiver receives the encrypted contents and the key information to decrypt the encrypted contents by using the key information;
• the transmitter updates the key information based on a given condition;
• the receiver transmits the contents confirmation request for instructing transmission or confirmation of the key information held by the transmitter to the transmitter at a given timing;
• the transmitter acquires the random number included in the contents confirmation request and the key information being currently used, when the contents confirmation request is received;
• the transmitter transmits to the receiver at least one of a confirmation result showing whether the acquired key information coincides with the key information held by the receiver and the acquired key information, with the acquired random number, as a contents confirmation response for the contents confirmation request;
• and
• the receiver performs at least one of another instruction by the contents confirmation request unit and prohibition of decryption of the contents transmitted from the communication apparatus, when the key information added to the encrypted contents does not coincide with the key information being currently used by the transmitter.