Public key based authentication is not amenable for implementation in IoT environments due to its high complexity and resource requirements. In this paper, we propose a low-complexity scalable authentication framework suitable for low-power IoT environments and applications that uses physical layer information obtained from prior legitimate communications between the two parties as the source of shared secrecy. As in any physical layer information based authentication, we assume that each terminal generates a key at its side with its own channel measurements using a half-duplex radio and independent noise; hence, the extracted information (e.g., SNR values) or bit sequences after a quantization process are usually non-identical. In our approach, no part of the shared information (perfect or imperfect) is ever transmitted just for reconciliation of such differences. Our method allows a proper authentication in the event of some bit mismatches and handles them based on certain key properties of the Golay codes that we observed. The adversarial capability for obtaining successful authentication is shown to be extremely low.