Many IoT use cases have ultra-low latency and strong security requirements. But achieving both simultaneously is challenging. In this paper, as a use case, we consider the authentication of IoT devices for every transaction and develop a fast and secure authentication protocol. Our key idea is to leverage highly secure Physically Unclonable Functions (PUFs) and high-speed programmable switch and offload PUF-based authentication protocol to the switch. By doing so, it enables authentication of every transaction at network speed. In this paper, we demonstrate the feasibility of our idea by offloading the authentication protocol to a programmable switch with Tofino chip. Our preliminary experiments show that protocol offloading reduces authentication latency by 2-4 times and scales to a few hundred thousand IoT devices. © 2023 IEEE.