With rapid advancements in the technology, almost all the devices around are becoming smart and contribute to the Internet of Things (IoT) network. When a new IoT device is added to the network, it is important to verify the authenticity of the device before allowing it to communicate with the network. Hence, access control is a crucial security mechanism that allows only the authenticated node to become the part of the network. An access control mechanism also supports confidentiality, by establishing a session key that accomplishes secure communications in open public channels. Recently, blockchain has been implemented in access control protocols to provide a better security mechanism. The foundation of this survey article is laid on IoT, where a detailed description on IoT, its architecture and applications is provided. Further, various security challenges and issues, security attacks possible in IoT and their countermeasures are also provided. We emphasize on the blockchain technology and its evolution in IoT. A detailed description on existing consensus mechanisms and how blockchain can be used to overpower IoT vulnerabilities is highlighted. Moreover, we provide a comprehensive description on access control protocols. The protocols are classified into certificate-based, certificate-less and blockchain-based access control mechanisms for better understanding. We then elaborate on each use case like smart home, smart grid, health care and smart agriculture while describing access control mechanisms. The detailed description not only explains the implementation of the access mechanism, but also gives a wider vision on IoT applications. Next, a rigorous comparative analysis is performed to showcase the efficiency of all protocols in terms of computation and communication costs. Finally, we discuss open research issues and challenges in a blockchain-envisioned IoT network.

随着技术的快速进步，几乎所有周围的设备都变得智能并为物联网 (IoT) 网络做出了贡献。将新的 IoT 设备添加到网络时，在允许设备与网络通信之前验证设备的真实性非常重要。因此，访问控制是一种关键的安全机制，它只允许经过身份验证的节点成为网络的一部分。访问控制机制还通过建立会话密钥来支持机密性，该会话密钥在开放的公共渠道中完成安全通信。最近，区块链已经在访问控制协议中实现，以提供更好的安全机制。这篇调查文章的基础是物联网，其中提供了物联网、其架构和应用的详细描述。更远，还提供了各种安全挑战和问题，物联网中可能出现的安全攻击及其对策。我们强调区块链技术及其在物联网中的演变。重点介绍了现有共识机制以及如何使用区块链来克服物联网漏洞的详细描述。此外，我们对访问控制协议进行了全面的描述。这些协议分为基于证书、无证书和基于区块链的访问控制机制，以便更好地理解。然后，我们详细说明每个用例，如智能家居、智能电网、医疗保健和智能农业，同时描述访问控制机制。详细的描述不仅解释了访问机制的实现，也为物联网应用提供了更广阔的视野。下一个，进行了严格的比较分析，以展示所有协议在计算和通信成本方面的效率。最后，我们讨论了区块链设想的物联网网络中的开放研究问题和挑战。