In recent years, an RF (Radio Frequency) remote control is gaining widespread use, which enables an information processing apparatus to execute processing in accordance with an instruction from a user by transmitting a radio wave to an information processing apparatus such as a television set. Further, attempts to standardize the RF remote control are conducted by organizations.
For example, in accordance with near field communication standard IEEE (registered trademark) (Institute of Electrical and Electronic Engineers) 802.15.4, ZigBee (registered trademark) is standardized as specifications for a network layer, a security layer, and an application layer, which correspond to upper layer of IEEE (registered trademark) 802.15.4. The specification of ZigBee (registered trademark) is approved by ZigBee (registered trademark) Alliance as version 1.0. IEEE (registered trademark) 802.15.4 is completed at Standardization Committee of IEEE (registered trademark) as specifications for a physical layer and a MAC (Media Access Control) layer.
In addition, based on IEEE (registered trademark) 802.15.4, RF remote control standard ZigBee (registered trademark) RF4CE (Radio Frequency for Consumer Electronics) v1.0 spec is standardized by trade organizations. According to this standard, in order to prevent operation information input to a remote control by the user from being read and misused by a third party such as a neighbor, a key (encryption key) is shared between the remote control and the information processing apparatus desired by the user. The key is used mainly when operation information, credit card information, and the like are transmitted from the remote control to the television set, and works in a manner that the third party who does not know the key cannot intercept those pieces of information.
In receiving a key transmission request from the remote control (hereinafter, also referred to as “operation terminal”), the information processing apparatus such as the television set transmits elements of a key called key fragments, the number of which is equal to a key-dividing number (fragment number) written in the key transmission request, to the remote control. The remote control which has received the key fragments performs an exclusive OR of all elements, and acquires a final key. In general, a monitor, who is present at the other side of a wall or the like from the information processing apparatus and the remote control, does not have a satisfactory propagation path of a transmitted/received radio wave with the information processing apparatus or the remote control, and hence, cannot receive all of those key fragments without error and cannot receive a key.
There are disclosed various technologies for generating key fragments and transmitting the generated key fragments (for example, refer to Patent Literature 1).