1. School of Computer Science and Engineering, Pusan National University 1 , Busan 46241, Republic of Korea
2. SmartM2M 2 , Busan 48058, Republic of Korea
3. Blockchain Platform Research Center, Pusan National University 3 , Busan 46241, Republic of Korea
4. Air Solution R&D Laboratory, LG Electronics 4 , Changwon 51554, Republic of Korea