Patent ID: 6539478
Filing Date: 2003-03-25
Classification: G06F

Abstract:
In a system including a controller, a control device operating on the basis of control signals from said controller, and an operating terminal connected to said controller via a communication network, a method of performing remote operations for controlling said control device through use of said operating terminal comprising the steps of:providing each of said controller and said operating terminal with a common key and means for encrypting and decrypting using said common key; generating and storing a next operating rights code signal on said operating terminal; encrypting a combination of a control signal obtained from a user, said next operating rights code, and a current operating rights code stored from a previous operation, said encryption being performed using said common key; transferring a resulting encrypted message to said controller; decrypting said encrypted message on said controller using said common key, and decoding said message into said control signal, said next operating rights code, and said current operating rights code; determining whether said current operating rights code transferred for this operation is identical to an operating rights code transferred and stored from said previous operation; storing said next operating rights code that was transferred to said controller if said operating rights codes are identical; and operating said control device according to said transferred control signal.