## 4 Findings
### Other Works
#### 4.7.5 Mobile IoT Applications
\begin{table}
\begin{tabular}{p{56.9 pt} p{113.8 pt} p{113.8 pt}} \hline \hline \multirow{2}{*}{**Ref \#**} & \multicolumn{2}{c}{**Future Works**} & \multirow{2}{*}{**Notes**} \\  & \multicolumn{2}{c}{**(Open Issues)**} & \\ \hline  & & \(\bigstar\) Efficient mining scheme & \\  & & \(\bigstar\) Significantly small mining delay compared to PoW & \\  & & \(\bigstar\) Enhanced scalability & \\
[90] & ✗ & Compatibility with IoT business models & \\  & & \(\bigstar\) Interoperability among several TrustChains & \\  & & \(\bigstar\) Network overloading due to excessive exchange of messages between devices and server & \\  & & \(\bigstar\) The centralized server is used for storage & \\  & & \(\bigstar\) This approach is not implemented and evaluated yet & \\ \hline
[91] & ✗ & ✗ It does not support dynamic access control & \\
[92] & ✓ & ✗ It supports the fast and secure insert of the device in the perception layer & \\ \hline
[93] & ✓ & ✗ Improved access tracking & \\  & & \(\bigstar\) Provided efficient access control and data transparency & \\  & & \(\bigstar\) This approach is not implemented and evaluated yet & \\ \hline
[94] & ✗ & ✗ (m-l)-private PTAS sacrifices little efficiency in exchange for safety improvement & \\ \hline
[95] & ✓ & ✗ Simple & \\
[95] & ✓ & ✗ Support parallel computing & \\  & & \(\bigstar\) Error not passing & \\  & & \(\bigstar\) Not easy to attack & \\ \hline
[96] & ✓ & ✗ In order to achieve anonymity, public keys alone are not enough & \\  & & \(\bigstar\) Zero-Knowledge Proofs & \\ \hline  & & \(\bigstar\) Robust against several types of attacks & \\  & & \(\bigstar\) Low expected computation cost & \\
[97] & ✗ & ✗ Moderate scaling & \\  & & \(\bigstar\) Transparency and verifiability & \\  & & \(\bigstar\) Good resiliency & \\  & & \(\bigstar\) Does not include trust and reputation management & \\ \hline
[98] & ✓ & ✗ The proposed system includes auto-policy enforcement, on-chain policy management & \\  & & \(\bigstar\) It provides security, fee-less, trustworthy (without TTP), and scalability & \\  & & \(\bigstar\) In order to eliminate network congestion and reduce the latency, machine learning algorithms can be integrated & \\ \hline
[99] & ✓ & ✗ Increased security due to the hybrid approach that combined many lightweight cryptographic primitives with public and private keys & \\  & & \(\bigstar\) This approach is not implemented and evaluated yet & \\ \hline  & & \(\bigstar\) Protection of EHR against fraud & \\  & & \(\bigstar\) Interoperability of EHR data formats & \\
[100] & ✓ & ✗ Low cost & \\  & & \(\bigstar\) IoT data aggregator and sensor heterogeneity & \\  & & \(\bigstar\) Not feasible for a large-scale network & \\  & & \(\bigstar\) Block is mined instantaneously by the virtual nodes itself; thus, miners are needed & \\ \hline
[101] & ✓ & ✗ High resiliency against public blockchain modification and DoS, modification, appending, and 51\% attacks & \\  & & \(\bigstar\) This approach is not implemented and evaluated yet & \\ \hline
[102] & ✗ & ✗ This approach offers on-demand rescission, accountability, and improved privacy & \\ \hline
[103] & ✓ & ✗ Using file and data sharing, this approach improved intersectral collaboration & \\  & & \(\bigstar\) In terms of development and administration, it requires further accountability & \\ \hline \hline \end{tabular}
\end{table} 
Table 8: Future Considerations.