To provide a security guard key system provided with a connector shape and communication protocol which conform to general-purpose specifications and capable of the integral control of devices of different purposes and uses.

The security guard key system constituted of both a key part and key reading/writing device. The key part is provided with both a storage part to store license information and means of communications. The key reading/writing device is provided with both a means of communications to provide and receive information for and from the key part and a license control device to provide the right to use resources for specific users on the basis of the information on the key part. The means of communications are each provided with a general-purpose communication protocol which conforms to information household electric appliances or household information networks.