## 3 Recent Literature Analysis
### Cyber-Physical Systems
#### 3.2.2 Cyber Security of CPS  
The security of CPS is another topic regularly discussed within the most recent novel literature. In particular, the cyber security concepts of privacy and resilience were of primary concerns across studies, highlighting the current research focus. Healthcare is one such domain, where information privacy needs to be maintained, but also needs to be practically searchable with appropriate access quality [43]. Blockchain combined with Attribute-Based Searchable Encryption is one solution proposed to combat challenges associated with resource processing and centralization for healthcare CPS [43]. However, future work considerations highlight the need for further research into healthcare blockchain reward mechanisms to enable investment, in addition to the personalization of the blockchain to meet healthcare specific requirements, such as user revocation [43]. One study utilized blockchain as part of their healthcare CPS in order to assist in the transmission of secure data [19]. In an additional study, a blockchain-based framework was used to secure the Internet of Medical Things (IoMT), through decentralizing electronic health records, leveraging smart contracts, and applying anonymity and cryptographic algorithms [44]. The research aims to overcome extant challenges related to cloud computing and the standardization of security solutions; however, it highlights the need for future work to focus on quality of service and real-time capabilities [44]. Securing the Internet of Medical Things (IoMT) is a topic related to CPS for healthcare, where sensors within medical facilities exchange sensitive information, and thus may be a vector for attack [45]. One study proposed the use of authentication and key establishment which leverages Physical Unclonable Functions (PUF) in order to verify the legitimacy of connecting nodes [45]. Privacy considerations for CPS tend to be focused on healthcare and medical applications. Systems within these fields must handle and process data that is of a sensitive personal nature; however, they are not the only scenarios with this requirement. There is potential that the findings from these privacy papers may have cross-applicability to other CPS that manage personal sensitive data, such as electronic voting. Further research into this area may identify novel applications of existing research to new CPS problem sets. Building resilience into CPS networks is also a key cyber security concern highlighted within the recent novel literature. Sensor fault diagnosis in Wireless Sensor Network applications was identified as a priority due to the potential devastating implications of a CPS failure to both the cyber and physical components of the world [46]. Leveraging techniques such as Extremely Randomized Trees provided opportunities for machine learning algorithms to identify and diagnose faults; however, robustness testing across large numbers of sensors and faults was identified for future work [46]. Distributed resilient control for microgrids is investigated in the literature as one pathway to enable the restoration of services, equitable power sharing, and state of charge balancing, especially in environments that have the potential to exacerbate unreliable conditions and faults [47]. Additional protection from cyber-attacks is considered within the recent novel literature through the lens of Intelligent Transport Systems, where potential attack vectors such as spoofing, message falsification, Denial-of-Service, and burst transmissions are countered through cooperative adaptive control measures and distributed mitigation mechanisms [48]. These papers identify methods to assist in increasing resilience within CPS. However, they represent only a defined subset of potential obstacles, attacks or processing challenges that a CPS may face. There is therefore a need to invest in CPS research that integrates resiliency measures that can manage heterogenous stimuli and scenarios.