Communication device

A communication device comprising:

• a communication control unit generating a communication signal to be transmitted to an external source and transmitting the communication signal;
• and
• an encryption unit connected to the communication control unit through a wiring, wherein the encryption unit receives the communication signal from the communication control unit, encrypts the communication signal that is received, and then, returns the communication signal that is encrypted to the communication control unit, the communication control unit uses the communication signal encrypted by the encryption unit as the communication signal to be transmitted to the external source, wherein
• the communication control unit includes:
• a storage unit storing a predetermined communication signal indicative of a predetermined message and a target duration required for from a transmission of the predetermined communication signal to the encryption unit until a reception of the predetermined communication signal that is encrypted from the encryption unit;
• and
• a measurement unit counting an actual duration taken from the transmission of the predetermined communication signal to the encryption unit until the reception of the predetermined communication signal after the predetermined communication signal is encrypted and returned by the encryption unit, and
• when the actual duration counted by the measurement unit is longer than the target duration, the communication control unit determines that a fraudulent circuit is inserted into the wiring for fraudulently acting on the communication signal.