Block chain technology applied to cryptocurrencies is the dominant factor in maintaining the security of cryptocurrencies. This article reviews the technological implementation of cryptocurrency and the security and stability of cryptocurrency and analyzes the security support from block chain technology and its platforms based on empirical case studies. Our results show that the security support from block chain technology platforms is significantly insufficient and immature. Moreover, these platforms provide computational resources and benefits to the consensus algorithm selection for block chain practitioners. Second, encryption ensures the security of cryptocurrencies. On the one hand, the digital signatures identify the identity of the signatory and the transaction.