Abstract—In the last era the number of internet-connected devices surpassed the human population. IoT integration rate into human world equals at least five times the rate of electricity and telephony. Currently in 2020 the number of IoT devices is around 50 billion smart objects. This great invasion to our live requires extensive efforts for controlling and securing those devices. BlockChain (BC) is a distributed write-only ledger that eliminates the need for third party in securing and verifying transactions between peers. BC is considered the most powerful technique for securing transactions between IoT devices. In this work, a robust and scalable blockchain-based security framework for IoT is proposed. This framework comprises clients, device gateways, and administrators. IoT devices access BC through gateways. Ethereum BlockChain is utilized in addition to Ethereum smart contracts for enforcing a set of rules defined by the system administrator. Finally metrics that fulfill both efficiency and effectiveness of the proposed framework are introduced. In the results section, the proposed work provides robust and scalable security framework for the IoT devices under different attack probabilities in addition to satisfying the conditions of lightweight, transparency, and timeliness.
 

Index Terms—IoT, BlockChain, smart contracts, security, fog computing