Patent ID: 8064603

Claim:
An information terminal which is configured to operate as one of a source terminal and rendering terminal, wherein the information terminal, operating as the source terminal, comprises: a storing unit configured to store an encoded content; a first receiving unit configured to receive a rights object including rights information assigned to the encoded content and key information used to decode the encoded content, wherein the rights object is encoded using a public key and is transferred from a rights server via a communication network; a first decoding unit configured to decode the encoded rights object using a secret key paired with the public key; an extracting unit configured to extract the key information from the decoded rights object; a first session establishing unit configured to perform mutual authentication with another information terminal operating as the rendering terminal, and establish a secure session with the other information terminal operating as the rendering terminal if legitimacy thereof is authorized as a result of the mutual authentication; a first generating unit configured to generate a first common key; and an encoding unit configured to encode the extracted key information corresponding to the encoded content by using the first common key generated by the first generating unit, and transmit the encoded key information to the other information terminal operating as the rendering terminal via the secure session, and wherein the information terminal, operating as the rendering terminal, comprises: an acquiring unit configured to acquire the encoded content; a second session establishing unit configured to perform mutual authentication with another information terminal operating as the source terminal, and establish the secure session with the other information terminal operating as the source terminal if legitimacy thereof is authorized as a result of the mutual authentication; a second generating unit configured to generate a second common key that is identical to the first common key generated by the first generating unit; a second receiving unit configured to receive the encoded key information transmitted from the other information terminal operating as the source terminal via the secure session; a second decoding unit configured to decode the received encoded key information by using the second common key generated by the second generating unit; a playing back unit configured to decode and playback the acquired encoded content by using the key information decoded by the second decoding unit; and a discarding unit configured to discard the decoded key information after end of playback of the decoded content.