Security issues have long been the main obstacle of massive usage of RFID system. To elevate the security level, a novel implementation of public key cryptosystem NTRU is given. Considering the weak computing power, low cost, and limited power gained from the air interface. Special attention is paid to minimize the total computing time, area and power dissipation, by means of clock gating, pre-computing etc. The resulted circuit consists of 2837 equivalent logic gates, consumes 13.68μW power at 500kHz clock frequency. A comparison is provided based on the techniques used in this implementation.