## 2 Related Work  
The topic of MANET security and secure routing has been a focus of the research community for quite some time. One of the important reasons that attract this focus is the variety of attacks that have been defined. The work of different researchers has tried to solve these challenges. Many different types of attacks have been proposed so far, among them blackhole attack, wormhole attack, rushing attack, packet alteration attack and spoofing attack, _etc_. The authors in [2, 3, 4, 5, 6, 7, 8] have provided a detailed overview of various attacks. In this section, a brief overview of some of the existing work is presented and will focus on various attempts that have been published in the literature to mitigate and counter blackhole attacks and the use of cryptography. [PERSON] and [PERSON] [9] proposed Secure AODV (SAODV), one of the widely known security enhancements for AODV. SAODV takes into account the resource-limitation and dynamic nature of network nodes and does not depend upon any Certificate Authority (CA). For security purposes, it makes use of a digital signature and one-way hash chain to protect the packet. As suggested by the author, if the digital certificates are not used, an impersonation attack could happen. Therefore, the RouteReply (RREP) messages can only be generated by destination nodes; in the case of intermediate nodes replying to some RREQ, then it has to perform the activity of signing the packet twice; this process is known as double signature and adds an extra processing load. SAODV uses a hash chain to protect mutable fields like hop count. It further requires all the nodes of the network to have knowledge of the public certificates of other nodes. SAODV messages are significantly heavy due to the presence of digital signatures. As the SAODV uses an asymmetric cryptographic, each packet generated by the node requires a signature and every time it receives a routing message (even an intermediate node), it has to execute the verification process. Although it helps in communicating nodes to find secure paths, it is computationally heavy. [PERSON] and [PERSON] [10] proposed an approach in which the route requesting node waits for the responses from neighboring nodes, which includes the next hop details, for a predetermined time value. After the wait period is complete, the entries in the Collect Route Reply Table (CRRT) are cross checked to see if there is any repetition of the next-hop-node details or not. If any such information is found in the reply paths, it assumes the paths are correct or the chance of malicious paths is limited. The solution adds a delay and the process of finding a repeated next hop is an additional overhead. In addition, the focus here is to find non-malicious nodes only, and it does not focus on the integrity and confidentiality of the data packets transmitted. [PERSON] and [PERSON] [11] proposed an extension of AODV routing protocols known as Secure Route Discovery for AODV (SRD-AODV) to mitigate the effect of the blackhole attacks. In the proposed solution, depending upon network environment and possible node density, a threshold value for the Sequence number is defined, as AODV makes use of a Sequence number to maintain the fresh and loop free paths. In SRD-AODV, upon receiving the RREQ, the destination node compares the Sequence number present in the packet and its routing table. If the value is higher, the sequence number in the destinations routing table is updated, otherwise the higher value present in the table is used. When the sequence number reaches the threshold value, it is reset. Similarly, a check of the same nature is performed at the requesting node, but, if the sequence number is high, it ignores the RREP, assuming it to be sent by some malicious node. This solution counters the blackhole node attack but fails to counter any other form of attack. In [12], authors proposed a secure routing protocol, Authenticated Routing for _Ad hoc_ Networks (ARAN).