## 2 Related Work
Similarly, the fake source packet routing strategy is adopted in the forward random walk and bidirectional tree schemes [29], the fake network traffic-based scheme [30], the timed efficient source privacy preservation scheme [31], and the dummy uniform distribution, dummy adaptive distribution, and controlled dummy adaptive distribution protocols [32]. Often, the fake source packet routing protocols are criticized because of their high energy consumption, mainly because they rely on injecting a large number of fake packets to effectively protect the SLP. Furthermore, the protocols incur poor PDR and EED performance due to collisions between the packets. There exist several protocol designs which adopt both the phantom routing and fake source packet routing strategies. The protocols include the tree-based diversionary routing [4], the enhanced source location privacy based on data dissemination protocol [7], the probabilistic source location privacy protection protocol [20], and the distributed protocol that combines fake source routing and phantom source routing [33]. The tree-based diversionary routing functions as follows; a phantom node is established and a backbone route is created based on the location of the phantom node. Then diversionary routes are created as branches of the backbone route. As many as possible diversionary routes are created to form tree-based routing paths. Fake packets are distributed at the end of each diversionary route to effectively obfuscate the adversary. During the back tracing attack, the adversary is tackled with two branch routes each time, thus the possibility of a successful back tracing attack is reduced to half. Thus, the protocol achieves strong SLP protection. The protocol incurs significant energy consumption as a result of the long routing paths and the distribution of a large number of fake packets in the network. Furthermore, the distribution of a large number of fake packets results in high probability of packet collision and packet loss events. Thus, the protocol incurs long end-to-end delay and low packet delivery ratio. The protocol may be unsuitable for delay sensitive applications or applications which require reliable packet delivery. In the probabilistic source location privacy protection protocol, phantom nodes are generated around the source node with the consideration of a visible area. A weight value is computed at each node to determine the next-hop candidates. Fake sources are generated around the sink node to send fake packets and confuse the adversary. The transmission involves two types of packets, the real packets from the source node and the fake packets from fake sources. To preserve the SLP, real packets from the source node are routed to a phantom node by utilizing directed random-walk routing strategy. One fake source transmits packets to the sink node at a fixed period of time. The protocol is less effective at protecting the SLP due to the fact that it utilizes only one fake packet source at a time period. A single fake packet source may not be very effective at confusing the adversary. Also, the fake source is isolated from the real packet source, and the real packet routes and fake packet routes are not exactly homogeneous, making it less difficult for the adversary to differentiate the two regions of fake source and real source. If the two regions are obvious to the adversary, the adversary can focus the tracing back attack on the real packet source region and increase the probability of a successful back tracing attack. The enhanced source location privacy based on data dissemination protocol assumes a four quadrants square grid WSN with the sink node at the center of the grid. When a node wishes to send a packet to the sink node, the sink node generates a fake source and a phantom source depending on the location of the source node. A blast ring around the sink node contains nodes which are designed to flood packets inside the ring.