BlockChain (BC) has gotten a lot of interest because of its immutability and accompanying security and privacy benefits. BC has the potential to address the Internet of Things' security and privacy issues (IoT). BC, on the other hand, is computationally expensive, has limited scalability, and incurs significant bandwidth overheads and delays, making it unsuitable for use in the IoT. In this study, we propose a method that optimizes BC for use in IOT environment. we present a hierarchical structure that uses a private BC to increase scalability, reduce network overhead and delay. In the proposed method, devices with high-level resources build a network referred to as the overlay network on devices with low-level resources. The members of the overlay network manage the BC. The arrangement of the block managers at the overlay network level is two-dimensional which removes the focus from IOT management. We use trust technique and voting from direct neighbors to reduce network traffic and overhead costs. The use of factors such as trust, encouragement and penalty of block managers in the overlay network ensures accurate transactions in IOT. We use the new block manager authentication algorithm for authentication in the overlay network. The simulation results show that the proposed algorithm reduces packet overhead and delay in service delivery and increases the scalability of the BC in comparison to the system that uses the base BC. Furthermore, because in the proposed algorithm, the number of effective block managers in voting is limited to direct neighbors, the average time to confirm a block is significantly reduced. Manuscript profile