# Public Key-Based Authentication and En-Route Filtering Scheme in Wireless Sensor Networks
## 1 Introduction  
Wireless sensor networks (WSNs) have attracted a lot of attention recently, and have been applied in various applications, such as military sensing and tracking, traffic flow measuring, environmental monitoring, and real-time accident reporting etc. [1; 2; 3]. One major function of WSNs is to detect events of interest and deliver the event reports to the base station (BS) through multi-hop wireless paths. WSNs usually consist of numerous small sensor nodes that are resource starving and, as such, are highly constrained by battery power, storage, computation, data rate, and available bandwidth [4]. Due to the lack of tamper-resistant hardware, the sensor nodes in WSNs are vulnerable to be compromised. Once a node is compromised, all the security information stored in it can be used by the adversary. Then, the adversary can control the compromised node to launch various insider attacks, such as a false data injection attack [5], report disruption attack [6], selective forwarding attack [6] etc. These attacks can severely damage network function, and waste limited network resources such as energy and bandwidth, hence, severely affecting both data authenticity and availability. To defend against the aforementioned attacks, many en-route filtering schemes have been proposed. It was a common belief that the traditional public-key cryptography (PKC) was too complex, slow and power hungry and, thus, ill-suited for use in resource-constrained WSNs [7]. Due to this, most existing en-route filtering schemes [5; 8; 9; 10; 11; 12; 13] are generally based on symmetric-key cryptography. However, due to the inherent limitations of symmetric-key cryptography, these schemessuffer from the lack of authentication, scalability and resilience to node compromise [14]. Therefore, some researchers [15; 16] began to investigate the feasibility of using PKC on sensor platforms and showed that traditional PKC, such as RSA or elliptic-curve cryptography, is rather viable in WSNs [7]. Then, many PKC-based en-route filtering schemes [1; 6; 7; 17; 18; 19; 20] were proposed to filter out bogus reports at an early stage. These schemes have a few drawbacks, however; for example, some of them (the energy-aware routing and filtering scheme (ERF) [18] and the public-key based false data filtering scheme (PDF) [19]) are vulnerable to report disruption attacks and selective forwarding attacks. The digital signature assisted end-to-end data authentication scheme (DSEDA) [1] is resilient to report disruption attacks to a certain degree, but vulnerable to selective forwarding attacks. The authentication and en-route filtering scheme [6] and the location-based threshold-endorsement scheme (LTE) [7] are resilient to the two aforementioned attacks to a certain extent, however, they have high communication overhead and the security vulnerability of LTE was pointed out in [14]. Besides, none of these schemes consider detecting and punishing the malicious nodes, so the malicious nodes constantly can fool other nodes and consume the limited network resources. The authors propose a series of public key-based security mechanisms for WSNs based on the elliptic curve Pintsov-Vanstone signature scheme (ECPVSS) [21; 22] and [PERSON]'s secret sharing technique [23]. This study's main contributions are summarized as follows. First, the authors propose a mechanism for verifying the partial signatures. Accompanying this mechanism, the cluster head (CH) node can detect the invalid partial signatures at the very beginning of the report lifetime and, in this way, it can avoid generating an incorrect cluster signature for the event report. Second, the authors design a substitution mechanism to ensure that some trusted cluster nodes will participate in report generation when the valid partial signatures are inadequate, which can ensure that enough trusted cluster nodes will participate in report generation.