## 4 Proposed Routing Protocols  
Two new routing protocols are proposed, namely, the two-level phantom with a pursue ring (PhaP) and two-level phantom with a backbone route (PhaT) protocols. The proposed PhaP and PhaT protocols can be considered as modified versions of the probabilistic source location privacy protection routing protocol (ProbR) [20] and the tree-based diversiony routing protocol (TreeR) [4], respectively. The two main goals of the proposed protocols are to: (1) provide strong SLP protection throughout the WSN domain, and (2) control the communication overhead by removing the fake packet traffic in the network. The PhaP and PhaT protocols introduce a two-level phantom routing strategy. In the strategy, packet routing is done in three phases. In phase 1, packets are routed from the source node to the first level phantom node. The routing strategy for phase 1 in the PhaP and PhaT are adopted from the ProbR and TreeR protocols, respectively. Phase 2 involves the process of packet routing from the first level phantom node to the new second level phantom node using two new routing strategies. The new routing strategies are explained in details in the next sub-sections. Phase 3 involves the process of packet routing from the second level phantom node to the sink node. In PhaP, phase 3 is accomplished by utilizing a directed random-walk strategy. In PhaT, phase 3 is accomplished by utilizing a random backbone route which is generated between the sink node and a neighboring node of the the second level phantom node. A new backbone routing strategy is proposed. The key differences between the routing strategies of the proposed and existing protocols are highlighted in Table 2. For both PhaP and PhaT protocols, the two-level phantom routing strategy is designed to provide two adversary confusion phases. The first level phantom node provides first level adversary confusion phase while the second level phantom node provides second level adversary confusion phase. If an adversary embarks on back tracing the routing paths, it encounters two levels of adversary confusion phases. Thus, strong SLP protection is guaranteed. The proposed PhaP and PhaT routing algorithms are summarized in Algorithms 1 and 2, respectively.  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**PhaP** & **ProbR** \\ \hline \(\bullet\) & Packets from the first level phantom nodes are routed to a new random second level phantom node located in the pursue ring. Then, the packets are forwarded to the sink node. & \(\bullet\) & Packets from the equivalent first level phantom nodes are forwarded directly to the sink node. \\ \(\bullet\) & Only real packets are transmitted in the WSN domain. & \(\bullet\) & Real packets and fake packets are transmitted concurrently. \\ \hline \hline
**PhaT** & & **TreeR** \\ \hline \(\bullet\) & Packets from the first level phantom nodes are routed to a new random second level phantom node located near the network border regions. Then, the packets are forwarded to the sink node through a backbone route. & \(\bullet\) & Packets from the equivalent first level phantom nodes are forwarded directly to the sink node through a backbone route. \\ \(\bullet\) & Only real packets are transmitted in the WSN domain. & \(\bullet\) & Real packets and a large number of fake packets are transmitted concurrently. \\ \hline \hline \end{tabular}
\end{table}
Table 2: Key differences between the routing strategies of the proposed and existing protocols.