In a gearbox device, a housing is formed with a hole-confining wall portion. The nanoparticles have characteristics that result in minimal retention of the particles in the body compared to other nanoparticles. Furthermore, the circuit has a second input for supplying a second signal which is connected to a control input of each basic element. Potential participants respond to the conference invitation and may make changes to, or modify, the attributes of the proposed conference. When the second decryption key is generated, the update instruction control unit considers the second key generation point in time to be the update timing from the first decryption key to the second decryption key so as to control the update instructing unit to issue the update command.