Blockchain platform allows the maintenance of a shared distributed ledger, which can be simultaneously read/modified by participants without being owned/controlled by a central unit or person. The transparency of the blockchain technology has inspired several IT engineers leading to the development of application, projects, and startups in the financial sector as in areas related to IoT, public and social services, security and privacy, reputation systems, and so on. This article focuses on important blockchain features and summarizes security and performance issues. We hope this work motivates unexperienced researchers to tackle security and privacy issues of bitcoin systems to provide a roadmap for blockchain developers when selecting appropriate techniques in different scenarios, as to aid researchers in considering it for future research topics.

blockchain, security, attack type, P2P.