# The Security of Big Data in Fog-Enabled IoT Applications Including Blockchain: A Survey
## 6 Blockchain: A Versatile Security Solution
As fog computing possess a distributed computing environment, it is impeccable to use distributed security mechanisms to secure network resources and data transactions, such as distributed trust and security solutions. Therefore, blockchain technology offers good grounds for fog-enabled IoT systems to build and manage distributed and decentralized trust and security solutions. The independent consensus among fog nodes and blockchain security architecture secure the network when the new device connects itself to the fog network. Furthermore, it can also detect and isolate the malfunctioning or compromised node to protect the whole system from any security breach. Therefore, this provides the much needed self-healing capability to the fog-enabled IoT systems. For complete success of IoT systems, it needs a new and efficient mechanism of security as the traditional security system and mechanism are unable to cope the challenges posed to this architecture. Therefore, industrial cyber-security systems should come with data securing mechanism to protect big data along with active corporation and control among connected devices [164; 165]. Moreover, all the fog-enabled IoT applications store large quantity of data for different purposes, such as enterprises store data related to their customers for observing their trends related to their specific interest which causes the privacy concerns. Among this, most of the issues arise due to intervention of third-party apps and services. Blockchain systems can provide highest possible security measures in this regard. The most important feature of blockchain is the introduction of secure storage and transmission by digitally signed documents for enhanced protection and privacy. Moreover, this technology may possibly offer an effortless infrastructure to directly transfer data among IoT devices for secure communication through a reliable time-stamped contractual handshake. These applications are widely used in trade and finance departments due to their sensitive nature for identity validation of users [166]. There exists some state-of-the-art systems in IoT domain [167; 151; 168; 169]. For the smart city, [PERSON] and [PERSON] [170] proposed a hybrid network architecture combined with Software Defined Networking (SDN) and blockchain. The authors also proposed a blockchain based scheme for distributed vehicular networks in [171]. In [159], they used SDN and blockchain technology for IoT based transport management system using a distributed mesh network infrastructure. For big data, BigchainDB [158] was used for increased throughput and to cater latency issues with the help of decentralized blockchain system. A literature review on applications of blockchain is presented in [156], mentioning the usability of blockchain in IoT domains. The authors also highlighted integrity and adaptability issues of blockchain in IoT systems. [PERSON] and [PERSON] [172] \begin{table}
\begin{tabular}{p{142.3 pt} p{142.3 pt} p{142.3 pt}} \hline \hline
**Description** & **Advantages** \\ \hline A blockchain solution for preserving data privacy in Internet of Things using smart contracts along with a firmware scheme using blockchain for prevention of fraudulent data [162] & \(\bullet\) & Trustless access control management constrained IoT device tampering to prevent fraudulent data \\ \hline A blockchain-based proof of concept for securing consumer/home-based IoT devices and the networks by using Ethereum [163] & \(\bullet\) & No significant storage and CPU overheads Utilization of built-in asymmetric key encryption and digital signatures present in Ethereum protocol \\ \hline \hline \end{tabular}
\end{table} 
Table 6: _Cont._compared both cloud and fog platforms to justify which performs better for blockchain based IoT networks. According to their findings, the fog-based scenarios outperform the cloud-based IoT systems. The security system equipped with blockchain-based security satisfies all the requirements of fog-enabled IoT systems by enhancing independent operation between all the connected nodes.