## 4 Proposed Scheme
### Identity, Route, and Location Privacy (IRL)
Because of the concept of _direction_ (Section 4.1), proposed schemes provide more length variation and because of the _randomness_ (Section 4.2) proposed schemes provide high path variation. Incorporation of both features offer high path diversity. In order to analyze the path diversity behavior, we have organized 300 sensor nodes in a 10 by 30 grid manner. The rest of simulation parameters are given in Table 4. In the simulation, a single source node (ID: 224) generates 100 data packets for the base station. Figure 7 shows the path diversity (in terms

Figure 7: Path diversity of privacy schemes. of path length) of the IRL, PSR-hop and PSR-sec schemes. The average path taken by the PSR-hop, IRL and PSR-sec is 22.12, 36.81 and 38.17, respectively. It indicates that the IRL scheme incurs more delay as compared with the PSR-hop scheme and less delay as compared with the PSR-sec scheme. This figure also indicates that the IRL scheme has more path variation as compared with the other schemes, which creates more difficulties for the adversary to trace back the source from the captured packets. Figure 7 also shows that some packets took longer paths in the IRL scheme as compared with others. This is due to the fact that the source or en-route node did not find any trusted node in its forward direction, so the packet is relayed back in the backward direction. If we assume that each node has \(p\) probability to be trusted and all probabilities are independent of each other, then the total probability \(P_{b}\) for a node \(i\) to relay the packet in the backward direction is:

\[P_{b}(i)=\prod_{k=1}^{m_{f}}\left(1-p_{k}\right) \tag{11}\]

where \(m_{f}\) represents the number of nodes in the forward direction. Figure 8 shows the result of 100 simulation runs in which we have assumed that each node has equal probability to be trusted and un-trusted. It shows that, as the neighborhood size increases, the probability of the packet to move in the backward direction decreases sharply. ### Discussion

From the memory, energy and path diversity analysis, we see that our solution is optimal especially with respect to the PSR-hop scheme. However, at a modest cost of memory and energy, our solutions provide full network level privacy as compared with the other existing schemes. This cost is justifiable because we have additionally achieved trustworthiness and reliability (in terms of packet reach-ability). With this level of resource consumption, our solutions can easily be used on real sensor nodes, for example, MICA2 sensor node has ATMega 128L micro controller (8 MHz @ 8 MIPS), 128 Kbyte program flash memory, 512 Kbyte measurement (serial) flash, and 4 Kbyte EEPROM [42]. ## 6 Conclusions and Future work

Existing privacy schemes of WSNs only provides partial network level privacy. Providing full network level privacy is a critical and challenging issue due to the constraints imposed by the sensor nodes (e.g.,

Figure 8: Probability of a packet to move in the backward direction. energy, memory and computation power), sensor network (e.g., mobility and topology) and QoS issues (e.g., packet reach-ability and timeliness). Therefore, in this paper we proposed the first full network level privacy solution that is composed of two new identity, route and location privacy algorithms and data privacy mechanism. Our solutions provide additional trustworthiness and reliability at modest cost of energy and memory. We also proved analytically that our solutions provides protection against an adversary who is capable of performing privacy disclosure attacks such as eavesdropping and hop-by-hop trace backing. In our future work, we will evaluate our proposed schemes from the perspective of computation cost that is required to perform encryption and random number generation. ## Acknowledgments

This research was supported by the MKE (Ministry of Knowledge Economy), Korea, under the ITRC (Information Technology Research Center) support program supervised by the NIPA (National IT Industry Promotion Agency) (NIPA-2009-(C1090-0902-0002)).