Block chain technology has been known as a cryptocurrency platform since the emergence of its first and largest application, bitcoin. Blockchain contributes to the process of changing low-trust centralized transaction ledger held by a single third party, to high-trust decentralized form held by different verifying nodes. Due to its decentralized nature and security robustness, blockchain has big potentials to be applied in various fields beyond cryptocurrency. This paper aims to provide readers a more complete literature review of blockchain, compared with existing works. We introduce and explain various security properties of blockchain, provide a taxonomy of blockchain-based applications, and discuss challenges of blockchain in terms of security and performance. Furthermore, some research directions are given in the last section of the paper.