# Hyperledger Fabric Access Control for Industrial Internet of Things
## 1 Introduction  
Industry 4.0, or the fourth industrial revolution, is the trend of future development to achieve smarter manufacturing processes. The Industrial Internet of Things (IIoT) is a branch of IoT that connects industrial assets and provides the best solution to the difficulties encountered in the manufacturing industry, focusing on the industrial sector, and generating data to help decision makings. It has the potential to improve and enhance industrial assets, such as machinery and equipment, control systems, business processes, etc., which leads to the smart industries. IIoT interconnects industrial systems and physical objects using sensors and actuators. With the integration of wireless sensor networks, communication protocols, and Internet infrastructure, IIoT can provide smart and efficient industrial operations. Nevertheless, it is a technology of processing and exchanging large amounts of confidential data between various industrial machines, which could be exposed to multiple cyber threats. As of today, the security level of many IIoT devices is low. The lack of a complete key management system, high-efficiency identity authentication, low fault tolerance, and many other problems have made the IIoT devices easy targets for the attackers to access illegally, causing serious consequences [1, 2]. Access control is a common technology protecting resources from unauthorized access and has been widely used in various systems and environments. The traditional access control methods include discretionary access control (DAC), role-based access control (RBAC), and mandatory access control (MAC). However,these methods were designed for centralized systems with the following shortcomings: single point of failure, low scalability, low reliability, and low throughput. These are the major challenges for traditional access control to meet the requirements of IIoT devices. To solve the emerging security challenges of IIoT, there have been many proposals to use blockchain technology due to its decentralized nature. The integration of blockchain and IIoT has many advantages in improving and solving certain security issues. Blockchain is a distributed ledger technology that uses cryptographic sealing and tamper-proof technology to connect multiple nodes in a peer-to-peer (P2P) network without any involvement of the third party using the consensus algorithms such as Proof-of-Work, Proof-of-Stake, Proof-of-Assets, Proof-of-Elapsed-Time, Byzantium Practical Byzantine Fault Tolerance, etc. [3; 4]. [PERSON] et al. [5] proposed an access control scheme based on Ethereum smart contracts which include three smart contracts: access control contract (ACC), judge contract (JC), and registered contract (RC). ACC implements policy-based authorization by checking the behavior of the object. JC is used to judge the wrong behavior and return the corresponding punishment. RC is used to register the above two smart contracts and provide updates, deletions, and other operations. The architecture is implemented through a personal computer, a laptop, and two Raspberry Pis. [PERSON] et al. [6] proposed a security-based Fabric-based data transmission technology and implemented a transaction center in the IIoT, which solved the problems of low security, high management costs, and difficult supervision. [PERSON] et al. [7] proposed a decentralized access control scheme for Internet of Things (IoT) devices using a single smart contract to reduce the communication cost between nodes. Nodes, also known as management centers, are designed to interact with devices, avoiding direct interaction between blockchain and IoT devices. It leads to six advantages: immediacy, accessibility, parallelism, lightweight, scalability, and transparency. [PERSON] et al. [8] proposed an attribute-based access control method for the IoT, which saves attribute data through the blockchain. This method avoids data tampering and simplifies the access control protocol to meet the computing power of IoT devices.