## 4 Proposed Solution
### Packet Transmission at Source Node
In [10], the approach proposed by the authors depends upon multiple route replies, which ESTA also relies on, but in the approach of [10], the intermediate nodes can also reply, which is prohibited in ESTA. In addition, no comparison of the common nodes is done in ESTA as the routes formed are dis-joint paths. Even after introducing delay to ensure correctness of the path, the multiple path transmission is not done which could help in load balancing. In addition, the integrity of the data packets cannot be ensured in case of passive attacks, which ESTA can handle. The solution proposed by [PERSON] and [PERSON] [11] is based on a consideration of network size and density which defines the maximum value for the sequence number. In the true sense of MANETs, it is not possible to judge these parameters until it is a pre-defined network defying the charter of the _ad hoc_ networks. Whereas ESTA does not depend upon any such considerations, it can scale well as the network size and density grows as shown in the simulation results. In the approaches of [12,14,15], the use of CA is taken into consideration, which ensures that authentic nodes are able to join the networks, but this can make the network susceptible as a single point of failure and also defies the true nature of _ad hoc_ networks. ESTA, in contrast, make use of trust values rather than Certificate Authority which helps in evaluating which helps in evaluating the goodness of the paths used and excludes the non-performs paths. Finally, it can be summarized that ESTA does not make use of CA or extra processing at intermediate nodes in terms of computations and still performs well in a variety of scenarios. The basic concern around the approach is the additional delay added along with a certain amount of overhead introduced by the new control packets. ## 8 Limitations and Future Work

In the current form of the proposed solution, use of a data structure with the name of SuperList is being used, which would be generalized in future research tasks. The use of trust in the current form is based on the direct observation that we would extend its scope by gathering the trust information from other peer nodes. Then, a generalized trust value would be assigned to the nodes. This will also help the approach to isolate the malicious non-performing nodes. Further, in the future, the focus would be to reduce and optimize the extra delay introduced in the protocol and add the Intrusion Detection Scheme (IDS) mechanism to nail down the actual malicious node. ## 9 Conclusions

In this paper, a new protocol ESTA for secure transmission of data in the case of a blackhole node attack in a MANET is proposed and evaluated. The proposed protocol makes use of multiple paths for data transmission and this process of route formation is not computationally heavy. Still, it is successfully able to suppress the non-performing paths. It makes use of a combination of trust and asymmetric cryptography to ensure integrity and authenticity of the data packets. Based on the simulation results, it can be concluded that, in various scenarios, the performance of ESTA is better than AODV, but it also introduced an additional delay at the cost of security. ## Author Contributions

This paper is the result of research conducted by authors on a topic for fulfillment of a Ph.D. The main idea was proposed by [PERSON] and further refined by [PERSON]. [PERSON] was mainly involved in developing the proposed protocol. Extensive simulations for testing, verifying, and getting the results for the analysis of the proposed model was carried out by [PERSON] under the guidance of [PERSON]. The authors have read and approved the final version of the manuscript. ## Conflicts of Interest

The authors declare no conflict of interest. ## References

* (1) [PERSON]; [PERSON]; [PERSON] A mechanism for detection of cooperative black hole attack in mobile _ad hoc_ networks.