Abstract: Hardware security has become more and more important in current information security architecture. Recently collected reports have shown that there may have been considerable hardware attacks prepared for possible military usage from all over the world. Due to the intrinsic difference from the software security, hardware security has some special features and challenges. In order to guarantee the hardware security, academia has proposed the concept of the trusted integrated circuits, which aims at a secure circulation of IC design, manufacture and chip using. This paper reviews the main problems of the trusted integrated circuits, and concludes the four key domains of the trusted IC namely the trusted IC design, trusted manufacture, trusted IP protection and trusted chip authentication. The main challenges in those domains are also analyzed based on the current known techniques. Finally, the main limitations of the current techniques and the possible future trends are discussed at the end of the paper.