## 3 Background and Literature Survey  
There are many solutions that have been presented to solve the problems of SLP and BLP. [PERSON] _et al._[8] discussed some of the solutions for SLP but they did not aim to create a survey. The comprehensive survey for SLP was presented in the work by [PERSON] _et al_. [4], where they categorized the solutions into eleven groups. They have discussed many solutions and compared them in terms of power consumption, the attack/threat model, view of the network, exposed information, and efficiency in providing SLP. They also discussed some issues that each solution exhibits. Anonymity is an old issue that was discussed for mobile networks, Ad Hoc networks and Internets. Recently, it has become a concern for WSNs. We have identified solutions for location privacy using anonymity in WSN. We have included them chronologically in Table 1.  
An important solution against a global adversary introduced by [PERSON] _et al._[16] called efficient anonymous communication (EAC) provides sender, link and sink anonymity. We know that anonymity is not enough to achieve fortified end-to-end privacy. There are some solutions based on fake data sources where SNs send out fake packets to other nodes within the network. Some literature call them dummy packets. A fake packet does not contain any real information about any real events but it helps to obfuscate the real traffic and to divert the adversary by mimicking the presence of a fake source. The literature shows reasonable solutions using fake sources. Some of them are designed to handle a local adversary and some of them are suitable for a global adversary. Some of the literature presume a certain routing scheme, topology, network and threat models. [PERSON] _et al._[17] introduced three different solutions to handle the global adversary problem. The first solution is the globally optimal algorithm (GOA). Each SN has a pseudo random number generator that defines the interval time. The second solution by [PERSON] _et al._[17], is the heuristic greedy algorithm (HGA) where SNs follow the same procedure as in GOA except that the SN does not know the complete topology, but it only has the information of its location and the seeds of its neighbors. The third solution by [PERSON] _et al._[17] is the probabilistic algorithm (PBA) where nodes still follow the procedure of HGA, except that they do not send fake messages at the end of every interval. It uses probability \(p\) to decide whether to send a fake message or not. The value of \(p\) will reduce the communication overhead at the expense of SLP. We can enhance SLP and BLP by having temporal privacy against the hop-by-hop trace attack or timing analysis attack [4]. There are some literature addressed this using issuing packet delay techniques. [PERSON] _et al._[18] introduced probabilistic reshaping (_PRESH_) to counter the adversary that uses timing analysis techniques and also introduced and upgraded PRESH to be extended probabilistic reshaping (_exPRESH_) to counter such a scenario. The SN will delay the packet in its buffer again up to \(D\) time. [PERSON] _et al._[19] introduced rate controlled adaptive delaying (_RCAD_). In this work, we shall enhance EAC, the efficient anonymous communicating protocol [16, 26]. An extension to EAC called _Enhanced Communication Protocol for Anonymity and Location Privacy in WSN_ (E\({}^{2}\)AC) was presented in [27]. We will call our scheme FAC, _a fortified anonymous communication protocol for WSN_. EAC does not handle the pseudonyms synchronization very well. There are many situations where the system will get unsynchronized. It also could not handle multi-colluding adversaries and lacks a mechanism for time correlation attack. Most of the other solutions do not handle global or multi-colluding adversaries. Each of the different solutions focus on certain selected attack scenarios. Our work is aimed to be comprehensive.