The present invention relates to a device and method that enable a security key to be shared using security key exchange between two terminals, and a system that supports the same. To achieve the above, an in-house generated public key is divided into two, said two public keys that have been divided are delivered to counterpart devices via different pathways, and the two public keys delivered from counterpart devices are used to predict the public key of the counterpart device. In addition, said predicted public key is verified, and said verified public key is used to form a master key. Subsequently, said generated master key is verified, and said master key that has been verified is used to exchange data with the counterpart device.