The most challenging challenge of bitcoin in 2018 is because bitcoin has never shown its innovation in technology so that bitcoin technology has become increasingly backward from some other crypto currencies. This is the most challenging bitcoin face because bitcoin must make improvements from various aspects when bitcoin wants to continue to maintain its position as the leader of crypto currencies. The challenge faced by bitcoin until now has not been filled with bitcoin at all so it makes bitcoin increasingly lose public trust. The loss of public trust is evident from many bitcoin owners who sell their bitcoin on a large scale because they do not believe in the future of bitcoin. When the sale occurs large-scale then the price will go down.