| Summary: | A key technology for the communication in the Industrial Internet of Things (IIoT) is the Open Platform Communications Unified Architecture (OPC UA). OPC UA is a standard that enables interoperable, secure, and reliable communication between industrial devices. To defend against cyber attacks, OPC UA has built-in security mechanisms that protect the authenticity, integrity, and confidentiality of data in transit. Before communicating securely, it is essential that OPC UA devices are set up in a secure manner. This process is referred to as secure provisioning. An improper provisioning can lead to weak or insecure OPC UA deployments that enable adversaries to eavesdrop or even manipulate communication between industrial devices. Such insecure deployments can also be maliciously provoked by adversaries who tamper with insecure provisioning solutions. Despite secure provisioning is essential for OPC UA security and usability, there exists no overview and systematic analysis on the patchwork of different solutions in industry and academia. This article presents the first investigation of secure device provisioning solutions for the OPC UA communication protocol. First, desired objectives and evaluation criteria for secure provisioning of OPC UA devices are defined. Next, existing and emerging OPC UA provisioning solutions are analyzed and compared based on the elaborated objectives and criteria. Additionally, an outlook into the future of OPC UA provisioning is given, based on solutions from the IoT domain. Finally, the analyzed OPC UA secure provisioning solutions are compared, recommendations are given, and research gaps are identified. It is shown that contemporary provisioning solutions offer an insufficient level of security. Emerging and future solutions provide much higher security guarantees but impose a tradeoff between usability and requirements on devices and infrastructures.
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