With the rapid growth of wireless communication, sensor technology, and mobile computing, the ad hoc network has gained increasing attention from governments, corporations, and scientific research organisations. Ad hoc and sensor network security has become crucial. Malicious node identification, network resilience and survival, and trust models are among the security challenges discussed. The security of ad hoc networks is a key problem. In this paper, we'll look at a few security procedures and approaches that can be useful in keeping this network secure. We've compiled a list of all the ad networks' descriptions with explanations. Before presenting our conclusions from the examination of the literature, we went through various papers on the issue. The taxonomy diagram for the Ad-hoc Decentralized Network is the next item on the agenda. Security is one of the most significant challenges with an ad hoc network. In most cases, cyber-attackers will be able to connect to a wireless ad hoc network and, as a result, to the device if they reach within signal range. So, we moved on to a discussion of VANET, UAVs security issues discovered in the field. The outcomes of various ad hoc network methods were then summarised in the form tables. Furthermore, the Diffie Hellman Key Exchange is used to investigate strategies for improving ad-hoc network security and privacy in the next section, and a comparison of RSA with Diffie Hellman is also illustrated. This paper can be used as a guide and reference to provide readers with a broad knowledge of wireless ad hoc networks and how to deal with their security issues.