Abstract: On ad hoc networks in which connection relationships among communication terminals constantly change, the processing load increases when authentication is performed each time a connection relationship changes. According to this invention, when communication terminals possess the same common key, mutual authentication is conducted with that common key, and when communication terminals do not possess the same common key, mutual authentication is conducted with a public key. Communication terminals that conducted mutual authentication exchange and retain a common key that they selected and common keys received from other communication terminals. When neither communication terminal possesses a common key at authentication, one terminal creates a common key and distributes it to the other terminal, and when one terminal has a common key it creates that common key and distributes it to the other terminal.

Abstract: On ad hoc networks in which connection relationships among communication terminals constantly change, the processing load increases when authentication is performed each time a connection relationship changes. According to this invention, when communication terminals possess the same common key, mutual authentication is conducted with that common key, and when communication terminals do not possess the same common key, mutual authentication is conducted with a public key. Communication terminals that conducted mutual authentication exchange and retain a common key that they selected and common keys received from other communication terminals. When neither communication terminal possesses a common key at authentication, one terminal creates a common key and distributes it to the other terminal, and when one terminal has a common key it creates that common key and distributes it to the other terminal.

Abstract: A control system for controlling a plurality of control elements, which are effective to control of a given controlled system, is disclosed. In this control system, a characteristic value representing the characteristic of a given controlled system to be controlled is detected, and respective optimum manipulated variables of the plurality of control elements are derived on the basis of the detected characteristic value.

Abstract: A control system for controlling a plurality of control elements, which are effective to control of a given controlled system, is disclosed. In this control system, a characteristic value representing the characteristic of a given controlled system to be controlled is detected, and respective optimum manipulated variables of the plurality of control elements are derived on the basis of the detected characteristic value.

Abstract: A shape controlling method for controlling the shape of a sheet rolled in a rolling mill, with the shape pattern of the sheet being approximated by a formula of an order of a large number, in accordance with the detected shape signals. Asymmetrical fundamental component (component of the first order) is extracted from the approximating formula. The control with respect to the fundamental component is allotted to the rolling reduction function, while the controls relative to the higher order asymmetrical components are conducted by other final control element than the rolling reduction function. The asymmetrical fundamental component causes winding of the sheet during rolling. By controlling the fundamental component separately from other components, it is possible to improve the shape of the rolled product while avoiding winding of the product under rolling operation.