## 6 Evaluation of the Proposed Protocol
### Security Evaluation
In the case of ordinary nodes impersonation, since SLEACH does not authenticate any node that joins the network, adversaries can insert intruder nodes to the network by taking any valid node ids (a problem caused by unauthenticated join request messages). These intruder nodes are able to insert false readings into the aggregated data that later on will be detected by the BS. The BS drops any aggregated data which contains data from unauthenticated nodes. Even though MS-LEACH also suffers from this attack, the best thing those intruder nodes can do is just to crowd the time slots since MS-LEACH has a pairwise key mechanism, while the pair-wise key mechanism in SecLEACH prevents the insertion of these intruder nodes into the network. Using the non-interactive identity-based key agreement we provide the pair-wise key mechanism to the proposed protocol. However, the impact would be worse if this attack is launched to impersonate CHs. SecLEACH allows CHs impersonation to take place since the advertisement messages are not authenticated. In SLEACH and MS-LEACH, the BS verifies the authenticity of the claimed CHs on behalf of the network. The proposed protocol inserts a digital signature into the advertisement messages to provide source authentication. An adversary node with strong radio power transmission may lure a lot of nodes to join its cluster. This attack can lead to many other types of attacks such as selective forwarding and sinkhole attacks. For LEACH-based protocols, the security aspect of the schedule message should be considered. The schedule message contains the TDMA schedule for nodes within a certain cluster to take turns in reporting their sensor readings. SLEACH and SecLEACH do not facilitate source authentication services to this message distribution. They allow any intruder to disrupt the transmission schedule in any cluster. The security analysis of Sections 3.3.1 and 3.3.2 describes how it happens. MS-LEACH and the proposed protocol provide source authentication service for this message distribution via keyed MAC. To generate MAC MS-LEACH uses a pair-wise key while ours uses a cluster key. Therefore, in comparison with the other LEACH-based secure routing protocols, the proposed protocol can address all possible attacks under observation. The proposed protocol is really in tight competition with MS-LEACH. MS-LEACH fails to provide authenticated join request messages though it has a pairwise key mechanism that can help to achieve this, while the proposed protocol provides authenticated join request messages that block illegitimate nodes from joining the network. Therefore justifying carefully the security requirements for every involved message in the protocol is important. The next evaluation is done on any possible attacks that attempt to hinder the proper data aggregation process. Here we compare the proposed protocol and its counterpart, ESPDA. The summary is presented in Table 4. Here we consider four attacks: eavesdropping, replay attack, node impersonation for specific CHs impersonation and message tampering. Both protocols provide message confidentiality service for the actual data and aggregated data transmission. Therefore they address eavesdropping attacks. The data aggregation process can be disrupted via replay attacks. In ESPDA, the distribution of \(\mathbf{r_{b}}\), pattern seed and permutation seed are encrypted using a static network-wide key. Therefore ESPDA allows replay attacks to take place. The proposed protocol prevents this attack using a counter mechanism. We include a cluster counters into the MAC computation of those data distributions. In ESPDA, a cluster member does not authenticate its CH (ESPDA does not provide a cluster formation description) since every node only shares a pairwise key with the BS. Any adversary can impersonate CHs and then launch other types of attack such as selective forwarding or sinkhole attacks. But one type of attack which is of concern in many secure data aggregation protocols is the stealth attack.