Communication device and communication method

A communication device comprising:

• an encoding unit which encodes given content signals by an encoding key and outputs encoded content signals;
• a key encoding unit which stores a static device key and a dynamic device key into a storage area in advance, and encodes the encoding key by the static device key and the dynamic device key, and outputs an encoded encoding key;
• a communicating unit which performs communications so as to record the encoded encoding key output by the key encoding unit into a predetermined area on a network, and further record the encoded encoding key in duplication, together with the encoded content signals encoded by the encoding unit into a predetermined device on the network;
• a key decoding unit which reads out the encoded encoding key from the predetermined area via the communicating unit, in response to a replay instruction from a user, and decodes the encoded encoding key into the encoded key by the static device key and the dynamic device key;
• a decoding unit which reads out the encoded content signals from the predetermined device via the communicating unit, and decodes the encoded content signals into the content signals by the encoding key decoded by the key decoding unit;
• a replaying unit which replays the content signals decoded by the decoding unit;
• and
• a key updating unit which updates the stored dynamic device key, when the encoding key is abolished.