Abstract
As a new promising distributed technology, blockchains have been widely applied since its inception. Its decentralization feature reduces the reliance on the trusted authorities and third parties. It can well solve the problem of data being tampered and increase data sharing. However, a blockchain system faces various security and trust issues, such as attacks against consensus mechanisms and propagation processes, which may make it store malicious information or delay data propagation. The work discusses the basic architecture of blockchains as well as its potential security and trust issues at data, network, consensus, smart contract, and application layers. Then, the related literature work is analyzed in terms of the issues at these layers. Some open issues are presented and discussed.