# A Survey on Emerging Blockchain Technology Platforms for Securing the Internet of Things
## 4 Analysis and Discussion: IoT Security and BC Components
### Consensus  
The Consensus mechanism provides trust in the blockchain, ensuring that every block is verified before being added to the blockchain. This has invariably been used in IoT-Blockchain to ensure data integrity in IoT system communication. Achieving consensus follows three processes: proposal (where a node proposes a block to be added), verification (another node validating the proposed block), and agreement (the majority node agrees that the proposed block is valid). This process employs algorithms such as Proof of Work (PoW), Proof of Stake (PoS), Byzantine fault tolerance (BFT), Proof of Authority (PoA), Practical \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**S/N** & **Work** & **Areas of Application** & **Technologies** & **Blockchain Platform** & **Consensus** \\ \hline
1. & [48] & Healthcare & Cloud and Fog computing & Ethereum & PoS, POW, PoA \\ \hline
2. & [40] &
\begin{tabular}{c} Authentication and \\ Access control \\ \end{tabular} & None & Ethereum & POS \\ \hline
3. & [39] & Vehicle communication & Cloud computing & Ethereum & PoW \\ \hline
4. & [41] & Voting System & Web & Ethereum & PoW \\ \hline
5. & [73] & E-Business & None & Ethereum & PoW and PoA \\ \hline
6. & [74] & Embedded System & FGPA & Ethereum & PoW \\ \hline
7. & [42] & Data Counterfeiting & Cloud & Ethereum & PoW \\ \hline
8. & [75] &
\begin{tabular}{c} Decentralised \\ Authentication \\ \end{tabular} & web & Ethereum & PoW \\ \hline
9. & [76] & Key Management & TLS Protocol & Ethereum & PoW \\ \hline
10. & [47] & Networks Attacks & None & Ethereum & Proof of Authority \\ \hline
11. & [49] & Data Sharing & Interplanetary File System & Ethereum & PoS \\ \hline
12. & [52] & Access Control & Lightweight cryptography & Hyperledger Fabric & PBFT \\ \hline
13. & [53] & Firmware Update & None & Hyperledger Fabric & PBFT \\ \hline
14. & [63] & Experimental IoT & None & Hyperledger Fabric & PBFT \\ \hline
15. & [50] & Edge Internet & None & Hyperledger & PBFT \\ \hline
16. & [77] & Access Control & None & IoTA & DAG \\ \hline
17. & [78] & TangleSim & None & IoTA & DAG \\ \hline
18. & [55] & Access Control & Lightweight cryptography & IoTA & DAG \\ \hline
19. & [58] & IOTA & None & IoTA & DAG \\ \hline
20. & [62] & Wearable & None & IoTx & Roll-DPoS \\ \hline
21. & [79] & Data Authorisation & Pebble Tracker & IoTx & Roll-DPoS \\ \hline
22. & [63] & Mobile Payment & None & IoTx & Roll-DPoS \\ \hline
23. & [61] & Home IP Camera System & Intel SGX & IoTx & Roll-DPoS \\ \hline
24. & [68] &
\begin{tabular}{c} Electrical Energy System, \\ Authentication \\ \end{tabular} & MQTT, TLS, and CA & IoTx & Roll-DPoS \\ \hline
25. & [66] & Prototype & Raspberry Pi and STM32 & Algorand & Pure PoS \\ \hline
26. & [68] &
\begin{tabular}{c} Electrical Energy System, \\ Authentication \\ \end{tabular} & MQTT, TLS, and CA & Algorand & Pure PoS \\ \hline
27. & [69] & None & None & Multichain & N/A \\ \hline
29. & [80] & Authentication & None & Multichain & DAG \\ \hline
30. & [71] & Industrial IoT & IPFS & Multichain &
\begin{tabular}{c} Proof of Rapid \\ Authentication \\ \end{tabular} \\ \hline
31. & [70] & Security & None & Multichain & NA \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Technologies in selected IoT-BC existing works and their areas of applications. Byzantine Fault Tolerance (PBFT), and Raft to achieve the agreement. This agreement helps to ensure the right data are added to the blockchain, especially in a large IoT system where several IoT systems depend on each other's data. It also guides against malicious actions by preventing unauthorised tampering and easily spotting malicious nodes. Research has shown that consensus algorithms also have flaws, and some of these are less effective in small IoT networks due to the required resources to carry out the attack. For IoT security using blockchain, default consensus algorithms are adopted on most platforms based on IoTeX, Algorand, Ethereum, and Hyperledger. A few exceptions also exist where other consensus mechanisms were proposed to support resource-constrained IoT devices.