Communication device and communication method

A communication method comprising:

• executing a network access authentication process with an authentication server in order to establish a connection to a network, the network access authentication process including generation of information shared with the authentication server;
• receiving an authentication result message from the authentication server when succeeding in the network access authentication process, the authentication result message containing an authentication result indicating success in the network access authentication process and an encrypted network key;
• generating a key transport key by use of the information generated in the network access authentication process;
• acquiring a network key by decrypting the encrypted network key contained in the authentication result message with the key transport key;
• encrypting data with the network key and transmitting encrypted data to the network;
• executing a first session check process of transmitting a session check request message to the authentication server and receiving a session check response message containing an encrypted first network key from the authentication server;
• acquiring a first network key by decrypting the encrypted first network key contained in the session check response message with the key transport key;
• encrypting data with the first network key;
• receiving encrypted data from the network;
• decrypting the received encrypted data with the network key;
• and
• executing, when failing in decrypting the received encrypted data, the first session check process,
• wherein the authentication result message and the session check response message contain encrypted key identifiers of the network key and the first network key,
• key identifiers are acquired by decrypting the encrypted key identifiers, and the key identifiers are managed in the way of being associated with the network key and the first network key,
• the encrypted data received by the communication unit is attached with a key identifier, and
• the received encrypted data is decrypted by use of the network key associated with the key identifier attached to the received encrypted data.

A computer-implemented communication device comprising:

• a network access authenticating unit configured to execute a network access authentication process with an authentication server in order to establish a connection to a network, the network access authentication process including generation of information shared with the authentication server;
• a communication unit configured to receive an authentication result message from the authentication server when succeeding in the network access authentication process, the authentication result message containing an authentication result indicating success in the network access authentication process, an encrypted network key and an encrypted key identifier of a network key;
• a key transport key generating unit configured to generate a key transport key by use of the information generated in the network access authentication process;
• and
• a network key acquiring unit configured to acquire the network key by decrypting the encrypted network key contained in the authentication result message with the key transport key, and acquire a key identifier by decrypting the encrypted key identifier with the key transport key, and manage the key identifier in the way of being associated with the network key,
• wherein the communication unit encrypts data with the network key and transmits encrypted data to the network,
• the communication unit receives encrypted data attached with a key identifier, and decrypts the encrypted data by use of the network key associated with the key identifier attached to the encrypted data,
• the network access authenticating unit executes a re-authentication process of a network access with the authentication server when the key identifier attached to the encrypted data is different from a latest key identifier acquired by the network key acquiring unit,
• the communication unit receives, when succeeding in re-authentication of the network access, a first authentication result message, the first authentication result message containing an authentication result indicating success in the re-authentication, an encrypted first network key and an encrypted key identifier of a first network key,
• the key transport key generating unit generates a first key transport key by using the information shared with the authentication server, which is generated in the re-authentication process,
• the network key acquiring unit acquires the first network key by decrypting the encrypted first network key with the first key transport key, and acquires a key identifier by decrypting the encrypted key identifier with the first key transport key, and manages the key identifier in the way of being associated with the first network key, and
• the communication unit encrypts data with the first network key.

A computer-implemented communication method comprising:

• executing a network access authentication process with an authentication server in order to establish a connection to a network, the network access authentication process including generation of information shared with the authentication server;
• receiving an authentication result message from the authentication server when succeeding in the network access authentication process, the authentication result message containing an authentication result indicating success in the network access authentication process, an encrypted network key and an encrypted key identifier of a network key;
• generating a key transport key by use of the information generated in the network access authentication process;
• acquiring the network key by decrypting the encrypted network key contained in the authentication result message with the key transport key, and acquiring a key identifier by decrypting the encrypted key identifier with the key transport key, and managing the key identifier in the way of being associated with the network key;
• encrypting data with the network key and transmitting encrypted data to the network;
• receiving encrypted data attached with a key identifier, and decrypting the encrypted data by use of the network key associated with the key identifier attached to the encrypted data;
• executing a re-authentication process of a network access with the authentication server when the key identifier attached to the encrypted data is different from a latest key identifier acquired;
• receiving, when succeeding in re-authentication of the network access, a first authentication result message, the first authentication result message containing an authentication result indicating success in the re-authentication, an encrypted first network key and an encrypted key identifier of a first network key;
• generating a first key transport key by using the information shared with the authentication server, which is generated in the re-authentication process;
• acquiring the first network key by decrypting the encrypted first network key with the first key transport key, and acquiring a key identifier by decrypting the encrypted key identifier with the first key transport key, and manage the key identifier in the way of being associated with the first network key;
• and
• encrypting data with the first network key.