Cyber-Physical Systems (CPSs) are becoming more automated and aimed to be as efficient as possible by enabling integration between their operations and Information Technology (IT) resources. In combination with production automation, these systems need to identify their assets and the correlation between them; any potential threats or failures alert the relevant user/department and suggest the appropriate remediation plan. Moreover, identifying critical assets in these systems is essential. With numerous research and technologies available, assessing IT assets nowadays can be straightforward to implement. However, there is one significant issue of evaluating operational technology critical assets since they have different characteristics, and traditional solutions cannot work efficiently. This study presents the necessary background to attain the appropriate approach for monitoring critical assets in CPSs' Situational Awareness (SA). Additionally, the study presents a broad survey supported by an in-depth review of previous works in three important aspects. First, it reviews the applicability of possible techniques, tools and solutions that can be used to collect detailed information from such systems. Secondly, it covers studies that were implemented to evaluate the criticality of assets in CPSs, demonstrates requirements for critical asset identification, explores different risks and failure techniques utilised in these systems and delves into approaches to evaluate such methods in energy systems. Finally, this paper highlights and analyses SA gaps based on existing solutions, provides future directions and discusses open research issues.

Mobile operators offer a wide range of value-added services (VAS) to their subscribers (i.e., mobile users), which in turn generates around 15% of the telecommunication industry revenue. However, simultaneous VAS requests from a large number of mobile devices to a single server or a cluster in an internet-of-things (IoT) environment could result in an inefficient system, if these requests are handled one at a time as the present traditional cellular network scenario is. This will not only slow down the server's efficiency but also adversely impacts the performance of the network. The current (insecure) practice of transmitting user identity in plaintext also results in traceability. In this paper, we introduce the first known protocol designed to efficiently handle multiple VAS requests at one time, as well as ensuring the secure delivery of the services to a large number of requesting mobile users. The proposed batch verification protocol (BAS-VAS) is capable of authenticating multiple simultaneous requests received by a large number of mobile users. We demonstrate that the protocol preserves user privacy over the network. The provider's servers ensure the privacy of the requested service's priority by performing sorting over encrypted integer data. The simulation results also demonstrate that the proposed protocol is lightweight and efficient in terms of communication and computation overheads, protocol execution time, and batch and re-batch verification delay. Specifically, we perform batch and re-batch verification (after detecting and removing malicious requests from the batch) for multiple requests in order to improve the overall efficiency of the system, as well as discussing time, space and cost complexity analysis, along with the security proof of our protocol using Proverif.