A chaotic entropy source based physical unclonable function (PUF) is proposed for the secure and low-power IOT platform. PUF is used to generate an encrypt key for data integrity of each transaction on IOT chain and device ID authentication to secure identification. The PUF use the true-random entropy source based on chaotic characteristics. Entropy core occupies 0.0045 mm(2) in 0.18 mu m CMOS technology and consumes 65 nW at 270 kbps throughput with 0.6 V supply. The proposed Entropy Source passes all NIST tests.