## 2 Underwater Acoustic Sensor Networks
It also reveals that based on a certain distance and some predefined frequency range, multi-hop communication can achieve better performance in cooperative transmission, but this method suffers from multiple node interference (internode). In [30] a centralized position cooperative algorithm was designed which is used for automatic identification of a direct path, and it has demonstrated that it can efficiently achieve cooperative positioning for underwater scenarios. In [31], an autonomous distributed target tracking for cooperative sensor networks that works in two aspects is introduced. The first aspect is an intelligent system for gathering target information of autonomous vehicle behaviors using a control system, and the second aspect deals with a novel approach of multiple functions behavior-based objects using an autonomous vehicle control system with reactive control of multiple environmental constrains. However, it does not consider moving nodes (i.e., mobile sensor nodes) in detecting the target node and tracking vast number of sensor simultaneously, thus, it is not suitable for underwater applications. UASNs are vulnerable to malicious activities due to the communication medium. Several different types of attacks can be targeted on UASNs such as jamming attacks on the physical layer, acknowledgment spoofing in the link layer or sinkhole attacks and selective forwarding in the network layer. Figure 3 illustrates how malicious nodes affect the performance of cooperation in UASNs [22; 32]. In this scenario node S wants to send message to node R. Node S chooses to send the packet to node n1 as a relay which is inside the routing vector toward the destination. Node n1 initially forwards the packet to n4, and it happens that n4 is a malicious node and n4 drops the packet. Node n1 notices that n4 is malicious, thus n1 sends a message to all its neighbors that n4 is malicious, and n1 selects n3 as a forwarding node which relays the packet to R (destination) [32]. Game Theory-Based Analysis (GTBA) proposed by [33] is an incentive-based cooperative method designed to solve the cooperation issues among regular nodes and malicious nodes. However, GTBA has not considered several attacks such as malicious node attack which makes unsuitable for UASNs. In [24], authors proposed a routing protocol for secure routing in which they utilize the primitive cryptographic concepts for the UASNs mobile nodes and fixed nodes. In [32] authors proposed a Dynamic Bayesian Signaling Game (SRPDBG) model to enhance the routing security to achieve a successful packet forwarding among nodes where they analyze regular nodes and malicious nodes. However, their approaches did not address cooperative mechanisms for end-to-end packet delivery in UASNs. A game theory approach described in [34] provides a solution to the problem of network security in MANETs which prevents conflict between sensor nodes with high mobility in terms of cooperation. The similar approach is applied in various fields such as computer networks, political science, behavioral biology and economics. In another work, a vector machine in support of attack detection and identification of malicious nodes in underwater wireless sensor networks (UWSNs) was proposed by [18]. [PERSON] et al. [35] discussed an energy evaluation scheme for varieties of digital signature approach to achieve authenticated forwarding and discussed suitability of using digital signature for UASNs despite its challenging features and characteristics. They adopted the concept of cryptographic mechanism of PKCs to achieve confidentiality and authentication. They also evaluate varieties of schemes for digital signature used in UASNs, where they classified them as short and long signature, however, the scheme only focuses on the efficiency of power consumption [35].