## 4 Findings
\begin{table}
\begin{tabular}{c c c c c} \hline
**Ref \#** & **Year** & **Country** & **Publication Type** & **Publisher** \\ \hline
[118] & 2020 & Australia & Journal & **Elsevier** Computers and Security \\ \hline
[119] & 2019 & China & Journal & **IEEE** Transactions on Industrial Informatics \\ \hline
[120] & 2018 & Vietnam & Conference & **IEEE** International Conference on Advanced Computing and Applications \\ \hline
[121] & 2020 & India & Journal & **Elsevier** Future Generation Computer Systems \\ \hline
[122] & 2019 & Australia & Journal & **Elsevier** Journal of Parallel and Distributed Computing \\ \hline
[123] & 2021 & Australia & Journal & **IEEE** Access \\ \hline
[124] & 2018 & China & Symposium & **IEEE** Symposium on Service-Oriented System Engineering (SOSE) \\ \hline
[125] & 2021 & China & Journal & **Springer** Cluster Computing \\ \hline
[126] & 2022 & Italy & Journal & **Wiley** Concurrency and Computation: Practice and Experience \\ \hline
[127] & 2019 & UAE & Journal & **IEEE** Access \\ \hline
[128] & 2021 & China & Journal & **IEEE** Systems Journal \\ \hline
[129] & 2022 & China & Journal & **Wiley / Hindawi** Wireless Communications and Mobile Computing \\ \hline
[130] & 2022 & USA & Journal & **MDPI** Future Internet \\ \hline
[131] & 2022 & Australia & Journal & **MDPI** Systems \\ \hline
[132] & 2022 & China & Journal & **IEEE** Internet of Things \\ \hline \end{tabular}
\end{table} 
Table 1: _Cont._  
Figure 5: Article distribution of the included studies by target application. values where each value represents the technical maturity of a technology; every three values describes a particular research phase. TRL phases are defined as research, development, and deployment. In order to reduce the complexity and initiate an understating of measuring what level each system is developed, we determined an appropriate value for each phase. For the research phase, 2 is selected, which indicates that the concept has been formulated. For the development phase, 5 represents the validation process in a relevant environment. Finally, for the deployment phase, 7 refers to the demonstration of a prototype in an operational environment. Overall, 79.09% proposed implemented design models (evaluated using simulation tools) [91, 92, 94, 95, 96, 97, 98, 100, 102, 103, 104, 105, 106, 107, 108, 109, 110, 111, 112, 113, 114, 115, 116, 117, 118, 119, 120, 121, 122, 123, 124, 125, 126, 127, 128, 129], and only one approach was implemented in a real-time environment [119]. The included approaches aimed to achieve various goals to enhance certain aspects (security or privacy) of IoT. For example, ref. [90] investigated the delay concerns, [93] discussed access control using a firmware update approach, ref. [94] presented a Privacy-preserving Thin-client Authentication Scheme (PTAS) to address privacy issues, heterogeneity and scalability issues are also discussed in [96], whereas ref. [99] aimed to address the access control for EHRs, a multi-tier blockchain framework for privacy-preserving EHRs is presented in [103], a data integrity check approach that does not require trusted third parties is designed using blockchain, bilinear pairing, and the Lifted EC-ElGamal cryptosystem in [113]. Some approaches focused on introducing lightweight techniques such as [114, 121, 122].