This paper proposes a cost-efficient reversible-based reconfigurable ring oscillator PUF (R3O PUF) for IoT and hardware security. The proposed design leverages the reversible logic paradigm and achieves better performance with significantly less hardware resources requirement compared to other state-of-the-art RO PUF designs while generating more challenge response pairs with using an equal number of configurable logic blocks of an FPGA. Experimental results show that the proposed model is suitable for enhancing a lightweight hardware security system especially for root of trust, authentication and key generation applications and eliminating the need for trading the security with power reduction.