The Internet of Things operates in vital areas and involves people, objects, and networks. Indeed, it ensures the interconnection and exchange of critical information that does not tolerate flaws. A successful attack on an object in one of these fields will cause fatal damage. Therefore, securing IOTs requires particular attention to the used protocols. It is essential to choose adapted protocols to the requirements of the objects and provide maximum security. Authentication is the first entry to IOTs that must be optimal and secure, without encumbering objects with limited capacities. To address this issue and to avoid concentration points, we present an improved authentication protocol based on the Blake2 hash function and the distribution of calculating OTP function. We will then evaluate, in terms of spatial and temporal complexity, the improvement brought to the IOT authentication process by the proposed process. We will prove that the use of these technics ensure a secure authentication that consumes less time and less memory.