# An Efficient Location Verification Scheme for Static Wireless Sensor Networks
## 5 Security and Performance Analysis
### Security Analysis
#### 5.1.5 Further Considerations on Known Attacks  
Beyond some of the attack strategies discussed above, there are several others that warrant discussion. Attackers working alone to forge the token will be severely limited in gathering the necessary data. This is because the MSRLV works in a decentralized and node-centric way. Thus, attacks by multiple colluding attackers stand a better chance of success. Attackers may use some known attacks, such as range-change, impersonation, wormhole or Sybil attacks, to bypass the location  
Figure 11: An example of sniffing on the msrToken. verification. Even though those attacks may not be designed to attack the location verification process, it is worth mentioning the effect of those attacks on the location verification. The range-change attack either shrinks or grows a sensor's transmission range, though it does not affect its listening range. The reason for this is that the transmission power can simply be adjusted by a change in the device's software, but increasing the reception ability requires additional hardware, such as a directional antenna. Thus, an attacker cannot forge the legitimate MSR token with this attack when its communication range does not cover the MSR between the verifier and its fake location. However, this attack can cause denial-of-service (DoS) because the change of transmission range can lead to the different token calculation at the verifier and the honest claimant. This is because the scheme is based on the assumption that the communication range of sensors is identical. The influence of the asymmetric communication range can be mitigated as discussed in Section 7. Impersonation is an attack where one sensor pretends to be another sensor by sending incorrect location information with using the honest sensor's identification information. This can cause DoS. However, this attack can be usually protected from through authentication. Even without authentication, attackers cannot gain much benefit through this attack when considering the following two cases. The first case is when an attacker in MSR impersonates the other sensor who is located outside the MSR. The second case is the opposite. In either case, D-filtering will mitigate the effect of the attack. Cases such as attackers in an MSR faking their location as the other location in the MSR and attackers outside an MSR faking their location outside the MSR are not effective attacks, so we did not consider them. The wormhole attack tunnels the packets between colluding sensors. This attack is one kind of collaboration attack discussed earlier. If the malicious sensors use the out-of-band channel which is not affected by the radio signal of the target WSN, they can speed up the delivery of the necessary information from their neighbors. Currently, the scheme proposed in this paper is vulnerable to this kind of attack. However, it can be mitigated by adopting wormhole detection mechanisms already developed by other researchers. A Sybil attack occurs when a malicious sensor represents multiple identities by creating a large number of pseudonymous identities. If the malicious sensor inside an MSR generates fake identities inside the MSR, there will be no problem because the verifier and the claimant can receive packets from the sensor, so the MSR token is not affected. However, a problem may occur in the other case, such that the attacker outside an MSR creates multiple identities inside the MSR. This attempt will affect the MSR token calculation. The verifier may revoke the verification because the tokens will not match. If the claimant is honest, there will be a DoS problem. Otherwise, the evil claimant will be detected. Table 1 shows the considerations of some known attacks on our scheme, including other location verifications. MSRLV achieves reasonable defenses when compared with the other schemes. In the table, \"Y\" means the scheme can defend the corresponding attack, whereas \"N\" is not.