The size and complexity involved in designing of electronic devices and systems is continuously outpacing the designer productivity. So, designers have to regularly thrive for new solutions in terms of design tools and methodology. IP (Intellectual Property) reuse methodology has been introduced to cope up with very large and complex designs. However, the IP core is vulnerable to many dangers such as copyright fraud, read-back attack, cloning, reverse engineering, etc. This paper provides a comprehensive review of current state-of-the-art of IP protection of FPGA-based IP core.