# The Security of Big Data in Fog-Enabled IoT Applications Including Blockchain: A Survey
## 5 Fog Computing Security Challenges
### Core-Network and Service Level Challenges
#### 5.1.3 Lightweight Protocol Design  
In real-time services, short-range communication between IoT and fog nodes one or two hops away may have a significant impact on the overall system performance. Due to the resource-constraint nature of IoT devices, there are several lightweight protocols designed to resolve these runtime issues. The authors of [84] provided multiple lightweight cryptography schemes including hash functions and stream chippers for secure end-to-end communication. \begin{table}
\begin{tabular}{l l l l l} \hline \hline
**Challenges** & **Solution** & **Limitations** \\ \hline \multirow{6}{*}{Identity Verification} & & & \(\bullet\) & Difficult identity authentication realization due to decentralized nature of fog computing \\  & \(\bullet\) & Identity authentication & \(\bullet\) & Difficult to manage the increased number of users \\  & \(\bullet\) & Co-operative authentication & \(\bullet\) & Authentication overhead and delays due to the mobility of IoT devices \\  & \(\bullet\) & Anonymous authentication & \(\bullet\) & Redundant authentication efforts are needed \\  & \(\bullet\) & Anonymous authentication & \(\bullet\) & Cooperation of fog nodes is needed \\  & & & \(\bullet\) & Privacy preservation is needed \\  & & & & \(\bullet\) & Response delay is not acceptable for real time services \\ \hline \multirow{6}{*}{Access Control} & & \(\bullet\) & Strong credential handling policies are needed to ensure trustworthiness \\  & \(\bullet\) & Role-based Access Control policy & \(\bullet\) & Federated and distributed access control architecture is needed due to mobility \\  & \(\bullet\) & Attribute-based Access Control policy & \(\bullet\) & and dynamic device management by the user \\  & \(\bullet\) & Device and key management & \(\bullet\) & Multiple device management is needed when accessed by a single user \\  & \(\bullet\) & Device and key management & \(\bullet\) & There must be consistent access policy for each user employing different devices to access the services \\  & & & \(\bullet\) & Key management is needed \\ \hline \multirow{2}{*}{Lightweight protocol design} & \(\bullet\) & Lightweight cryptographic techniques & \(\bullet\) & Need to design efficient lightweight protocols to support real time services of fog assisted IoT applications \\  & \(\bullet\) & Lightweight elliptic curve cryptosystem & \(\bullet\) & Need to design efficient lightweight protocols to support real time services of fog \\ \hline \multirow{6}{*}{Intrusion Detection} & \(\bullet\) & Host-based Intrusion Detection system & \(\bullet\) & It is challenging to design a robust, reliable and efficient IDS for fog computing due to its heterogeneous, decentralized and distributed architecture \\  & (IDS) & Local as well as global intrusion detection systems are needed in fog computing \\  & \(\bullet\) & Network-based IDS & \(\bullet\) & Behavior features sharing is needed among cooperative fog nodes; the way information is shared in a decentralized architecture to obtain quick detection of intrusion and its prevention is a challenging matter \\ \cline{1-1}  & \(\bullet\) & Distributed IDS & \(\bullet\) & of intrusion and its prevention is a challenging matter \\ \cline{1-1}  & \(\bullet\) & Mobile Sybil defence & \(\bullet\) & The basic information of the user is needed by the detector to differentiate between legitimate and Sybil user resulting in privacy leakage \\ \cline{1-1}  & \(\bullet\) & Cryptography-based Sybil defence & \(\bullet\) & In Sybil Defence, the data available on single fog node might not be enough to know if the user is Sybil or not because of crucial cooperation among fog nodes \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Core-network and service level challenges and solutions with respective limitations.