# Internet of Things and Blockchain Integration: Security, Privacy, Technical, and Design Challenges
## 3 RQ 1 and RQ 2--Current Challenges and Recommendations to Enhance BIoT Integration
### BIoT Design
#### 3.7.1 BioT Architecture  
The architecture supporting a BC needs to be tailored to the volume of traffic generated by IoT applications. Such an issue is more prevalent in classic cloud-based architecture, in which the node uses IoT gateways to send data to the cloud [113]. Traditional cloud-based IoT designs have several flaws such as the potential to disrupt the whole network by executing DoS attacks if only one device is compromised [112; 173]. Traditional cloud-based IoT designs rely on the cloud; however, the degree of reliance varies greatly in practice. There are additional gateways that do more complex functions (for example, sensor fusion), although, in most cloud-based applications, the majority of the processing is conducted in the cloud [4; 95]. The architectural issues connected with BIoT service providers have been examined in several designs suggested in the literature. [PERSON] et al. [91] examined four architectures, including totally distributed, distributed things, fully centralized things, and faux distributed things. In most situations, the completely distributed design must be followed by BIoT architectures; however, in cases of cost or power constraints, alternate \begin{table}
\begin{tabular}{p{113.8 pt} p{113.8 pt} p{113.8 pt}} \hline \hline
**Category** & **Challenge** & **Best Practice** \\ \hline Design & \multirow{4}{*}{
\begin{tabular}{} \end{tabular} } & \(\bullet\) & The completely distributed design is preferred for BIoT architectures; \\  & BIoT architectures & however, in cases of cost or power constraints, alternate techniques may be appropriate \\  & [4; 91; 95; 94] & \(\bullet\) & The BC process should be converted to a more competent layer, such as the fog, edge, cloud layers, and SDN \\ \cline{2-3}  & BC platforms [46; 57] & \(\bullet\) & Tradeoff between BC platforms based on different applications \\  & & \(\bullet\) & The character of different BC platforms is determined by their design goals \\ \hline \hline \end{tabular}
\end{table} 
Table 12: Recommendations for reducing the negative impact of design challenges. techniques may be appropriate. [PERSON] et al. [166] presented a hypothetical lightweight architecture for BIoT applications that reduce the communication overhead caused by BC. The suggested architecture is separated into three layers: smart home layer, shared storage layer, and cloud layer for distant storage. Regardless of the architecture described above, the BIoT design should take into account the limits and problems mentioned above. The BC-based theoretical architecture should consider delivering services and connecting heterogeneous IoT devices. This approach is based on a service discovery system that is built using multilayered hierarchical BC. Accordingly, the BC process should be converted to a more competent layer, such as the fog layer [128; 129; 142; 22], edge and cloud layers [146; 5; 12], cloud layer [130], or SDN layer [30; 94]. [PERSON] et al. [106] proposed a multilayered IoT design that aimed to reduce the complexity of BC deployment by establishing multiple layers in the IoT ecosystem and employing one BC at each level. [PERSON] et al. [174] provided another solution to the challenge of hosting a BC on typical IoT hardware that is resource-restricted. It looked at how FC and cloud computing architectures may be used in BIoT applications. The FC systems beat cloud-based systems in terms of latency reaction time under heavy transmission loads, according to the system's empirical performance evaluation. Another edge-based computing architecture was proposed by [175], in which the IEC 61,499 standard was used to create distributed and hierarchical platforms. To govern the fog nodes, the authors of [30] recommended using SDN for BIoT applications. Cloud computing is used to conduct computationally heavy activities, and FC is used to give low-latency data access. According to the findings, the suggested design improves throughput, reduces delays, and identifies numerous real-time IoT network threats.