## 4 Findings
\begin{table}
\begin{tabular}{p{34.1 pt} p{284.5 pt} p{284.5 pt}} \hline \hline
**Ref \#** & **Objective** & **TRL** \\ \hline
[90] & TrustChain is an innovative privacy-protecting blockchain-based network to overcome the issues associated with existing IoT networks and investigates how to eliminate privacy and delay concerns while preserving IoT network resources & 2 \\ \hline
[91] & A detailed analysis is provided, including enabling technology and IoT technology integration. In a smart IoT system, a case study is implemented using an Ethereum-based blockchain technology & 5 \\ \hline
[92] & In this study, the authors presented a blockchain-based decentralized IoT system. They developed various access strategies and implement them using smart contracts & 5 \\ \hline
[93] & In order to ensure that users have full control over their data and can track how it is used by third-party services, a system model is developed. They also proposed a blockchain-based firmware update approach that helps prevent IoT device tampering from causing fraudulent data & 2 \\ \hline
[94] & Employing private information retrieval to present a Privacy-preserving Thin-client Authentication Scheme (PTAS) for IoT devices & 5 \\ \hline
[95] & Propose an efficient and secure authentication private protection scheme using blockchain technology and the AES algorithm to encrypt the original IoT information; this study provides an IoT information security protection strategy that may effectively address IoT data storage issues & 5 \\ \hline
[96] & Deal with the heterogeneity and scalability of IoT networks by proposing a three-dimensional architecture with unique data structures. In addition, they propose the 3D-GHOST consensus mechanism for spacechain & 5 \\ \hline
[97] & Propose a trust evaluation mechanism, PoT consensus algorithm, and privacy protection mechanism based on the commitment scheme and rign signature & 5 \\ \hline
[98] & This paper addresses the scalability, privacy, and security issues by introducing a multi-layer-blockchain-based solution. It eliminates the need of Trusting Third Parties (TTP) through multiple-chaincode-based access control & 5 \\ \hline
[99] & Propose a novel patient-centered electronic medical record access control framework based on modified blockchain models that take into account the IoT’s resource constraints & 2 \\ \hline
[100] & Propose a dual-layer blockchain-IoT privacy-preserving approach based on swarm exchange techniques to support the seamless and secure transmission of user data via secure swarm nodes of peer-to-peer communications & 5 \\ \hline
[101] & Propose a blockchain-based architecture for e-health applications that provides an efficient privacy-preserving access control mechanism & 2 \\ \hline
[102] & Healthchain is proposed which is a privacy-preserving scheme designed for the healthcare domain, this approach is large-scale and is used to conduct fine-grained access control for health data. Furthermore, introduce a distributed file system called InterPlanetary File System (IPFS) & 5 \\ \hline
[103] & Proposing a novel protocol named Pseudonym-Based Encryption with Different Authorities (PBE-DA), this paper aims to achieve perfect privacy-preserving EHRs in a multi-tier blockchain framework & 5 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Objective and Technology Readiness Level.