# A Source Anonymity-Based Lightweight Secure AODV Protocol for Fog-Based MANET
## 1 Introduction  
Every application and system that is managed in a cloud and mobile cloud service is promising for big data processing. However, centralized cloud computing is unnecessary and inefficient for the management and application in a large-scale mobile ad hoc network. To relieve the computation and communication burden on mobility management in cloud computing, fog computing can be adopted. Fog computing was firstly proposed by Cisco in 2012 [1]. It is an extension of the cloud-based Internet. Moreover, it is introduced as an intermediate layer between mobile devices and the cloud in order to provide smooth, low-latency service delivery from the cloud to the mobile. In this paper, we combine a mobile ad hoc network with fog computing, and consider a new paradigm called a fog-based MANET, as shown in Figure 1.  
Generally, MANET is called a mobile Ad hoc network, which is composed of many organizing mobile nodes or terminals via routing protocol. What's more, the Ad hoc On-demand Distance Vector (AODV) protocol is just a typical routing protocol. Different from the clustered network, the mobile or fixed node can autonomously connect with the fog node, or construct a self-organizing, wireless, multi-hop, peer-to-peer, and dynamic mobile network, in which each node can act as a source node, a forwarding node, or a sink node. Each node is mobile, and can communicate with the single-hop node directly with wireless transmission technology. Then, its neighbor nodes decide how to transfer the data to the next hop, repeating this until reaching the fog node.  
In the OpenFog Architecture Overview white paper for fog-computing, \"Security implementations have many different descriptions and attributes such as privacy, anonymity, integrity, trust... \". To meet and achieve these requirements, the routing protocol in fog-based MANET aims at establishing high efficiency routing and transmitting information between nodes quickly. If any incorrect routing information is inserted into the network, or any routing information is tampered maliciously, the route will be misled, causing the whole network to become paralyzed. Hence, the security of the routing protocol is very important for the whole network. However, due to the characteristics of channel openness, dynamic topology, the lack of central authorization, distributed cooperation, and limited network capability, the traditional information security technologies that involve encryption [2], trust management [3], authentication [4], and secure network coding [5] are difficult to employ for solving the security issues of routing protocol directly and effectively.  
As a traditional on-demand routing protocol in MANET, AODV (Ad hoc On-demand Distance Vector) routing protocol also faces the same security issue. This is because AODV builds on the fact that all nodes trust each other, and does not take any security into consideration [6]. Although some secure algorithms have been proposed to improve the AODV security, they pay little attention to the impact on transmission performance and energy efficiency. Furthermore, the anonymity is not considered for the source node in AODV. An attacker can explore and locate the source node by using traffic analysis. In this paper, a Source Anonymity-based Lightweight Secure AODV routing protocol (SAL-SAODV) is proposed to meet the above requirements, which involves defending against attacks and achieving energy efficiency in MANET. The rest of this paper is organized as follows: In Section 2, the related works are highlighted in AODV and its evolution. Some preliminary knowledge and a security analysis are represented in Section 3. The SAL-SAODV protocol is proposed, simulated, and analyzed in Section 4. Finally, some concluding remarks are given in Section 5.  
Figure 1: Architecture of the Fog-based MANET.