Household terminal device and method and program for updating it

A household terminal device updating method comprising:

• a first transmission step for, in updating signature information unique to the device which is used to cancel copy protection and provided from a networked external server, transmitting an authentication command added with signature information already stored in order to create a first shared key shared with the server;
• a first reception step for receiving updated signature information encrypted using the first shared key which is transmitted from the server in response to the authentication command transmitted in the first transmission step;
• a second transmission step for transmitting an authentication command added with the updated signature information received in the first reception step in order to create a second shared key;
• a second reception step for receiving information of updating completion encrypted with the second shared key which is transmitted from the server in response to the authentication command transmitted in the second transmission step;
• a decision step for decrypting the information received in the second reception step using the second shared key and then making a decision of whether or not updating has resulted in success depending on whether or not the information of updating completion has been decrypted successfully;
• and
• an update step for updating the signature information when the decision by the decision means is that updating has resulted in success.

A program which causes a computer to perform:

• a first transmission step for, in updating signature information unique to the device which is used to cancel copy protection and provided from a networked external server, transmitting an authentication command added with signature information already stored in order to create a first shared key shared with the server;
• a first reception step for receiving updated signature information encrypted using the first shared key which is transmitted from the server in response to the authentication command transmitted in the first transmission step;
• a second transmission step for transmitting an authentication command added with the updated signature information received in the first reception step in order to create a second shared key;
• a second reception step for receiving information of updating completion encrypted with the second shared key which is transmitted from the server in response to the authentication command transmitted in the second transmission step;
• a decision step for decrypting the information received in the second reception step using the second shared key and then making a decision of whether or not updating has resulted in success depending on whether or not the information of updating completion has been decrypted successfully;
• and
• an update step for updating the signature information when the decision by the decision means is that updating has resulted in success.