# A Source Anonymity-Based Lightweight Secure AODV Protocol for Fog-Based MANET
## 2 Related Works
### Enhancing Security  
Since the secure transmission does not take account of the design of the AODV protocol, the way in which we can solve the increasing number of security issues becomes very important. At present, many secure schemes and algorithms have been researched for AODV protocol. These schemes and algorithms mainly focus on detecting, defending, or mitigating against specific attacks, including the sinkhole attack, the blackhole attack, and the Sybil attack. [PERSON] summarized the security issues of MANET, especially under the blackhole attack [7]. The non-secure boundaries of the MANET made it vulnerable to various threats like information leakage by eavesdropping or the Denial of Services (DoS) attack. On the other hand, the lack of infrastructure and a central management system in MANET made it difficult to detect, defend, and mitigate the different security attacks. [PERSON] et al. put forward a scheme to modify the AODV protocol in order to mitigate the blackhole attack in MANET [8]. The proposed scheme mainly created a Wait Time and Request Reply Tab table. [PERSON] and [PERSON] demonstrated a timer-based detection approach for identifying a blackhole node [9], modified the code of the AODV protocol according to the blackhole attack procedure, and proposed a timer-based method to overhear the next node action in the network layer. The proposed approach could effectively remove a blackhole node from MANET. [PERSON] et al. proposed a detection and defense scheme to eliminate the attacker, which carried out a blackhole attack [10]. The scheme could check the route reply against a fake reply based on \"Normal V/S Abnormal (anomaly) activity\". [PERSON] et al. put forward a secure knowledge algorithm [11], which aimed to detect and prevent the blackhole attack in the promiscuous mode. [PERSON] and [PERSON] proposed a solution to defend against a blackhole attack based on the first _RREP_ caching scheme in AODV protocol [12]. This solution could improve the performance in the routing protocol. Through enhancing the protocol along with the context aware TOR (Trusted On-demand Routing) model, [PERSON] and [PERSON] proposed a trust computation-based Sybil attack avoidance scheme in AODV [13]. The TOR model involved three major modules: the Node Manager, the Trust Module, and the Decision Manager. The Decision Manager secured the routing path on the basis of the trust value, which was computed in the Trust Module. The Node Manager reacted accordingly to AODV in response. [PERSON] and [PERSON] evaluated the throughput performance in AODV under a wormhole attack and Sybil attack [14], and gave the conclusion that the impact on throughput generated by the Sybil attack was greater than the impact of the wormhole attack. [PERSON] et al. proposed an approach to detect the wormhole based on the Hash-based Compression Function (HCF) [15]. Actually, the approach used the secure hash function to compute a value of a hash field for the _RREQ_ packet. In addition, [PERSON] and [PERSON] implemented and analyzed attacks against MANET in NS-2 using AODV routing protocol. These attacks involved the blackhole attack, the sinkhole attack, the selfish node behavior, the _RREQ_ flooding attack, the HELLO flood attack, and the selective forwarding attack [16]. They drew the conclusion that: if the malicious node was on the path from the source node to the destination node, the selective forwarding attack and the selfish node attack could cause a decline in the network performance. Furthermore, if the malicious node was connected to the source and destination, the sinkhole attack and the blackhole attack could severely affect the performance by transmitting false routing information and attracting all the traffic to themselves. [PERSON] et al. presented an analytical model [17] and estimated the performance of an AODV variant with a trust scheme. [PERSON] et al.