The present invention comprises an encrypting unit which encrypts input contents in a predetermined encryption mode, a header forming unit which forms a header portion including the encryption mode used for the encryption, and a transmitting unit which transmits a packet obtained by synthesizing the formed header portion and the encrypted contents. The method includes providing a metal substrate and a plurality of LED lights ; forming a graphene layer on the metal substrate in such a way that the graphene layer includes hollow sections formed to correspond to the LED lights ; mounting the LED lights to the metal substrate in the hollow sections ; and forming silicone layers in the hollow sections. The internal cooling circuit is formed at least partially between the convex suction side wall, the concave pressure side wall, and the tip wall.