Abstract: Wireless sensor networks (WSNs) are a new type of network integrating sensor technology, computer technology, and wireless communication technology. They are an effective method for acquiring physical information about the external environment. They can operate in harsh environments and obtain information that humans cannot obtain on their own. This paper mainly analyzes several specific attacks that threaten sensor network security and proposes appropriate solutions to ensure the secure operation of the network. Keywords: Wireless Sensor Networks, Routing Protocol, Key Management, Data Fusion [b][align=center]Research on the Security in Wireless Sensor Networks (WSN) ZHENGqiang, WANG-Xiaodong[/align][/b] Abstract: Sensor network is a new-style network that integrates sensor technology, computer technology, and wireless communication technology. It is an effective way to obtain external information. Sensor network can fix wireless sensor networks in areas that people cannot reach and obtain some useful information that people cannot access. This paper mainly analyzes specific attacks of security threats specific to sensor networks, advises suitable solution mechanisms, and assures network security. Keywords: Wireless Sensor Networks, Routing Protocol, Key Management, Data Fusion 1 Introduction With the continuous development of network technology, sensor technology, microelectromechanical systems (MEMS), and wireless communication technology, a new type of network technology has emerged—Wireless Sensor Network (WSN). Numerous sensors with communication and computing capabilities are connected wirelessly; they cooperate with each other, interact with the physical world, and jointly complete specific application tasks, forming a sensor network. Compared with traditional wireless communication networks and ad hoc networks, WSNs have the characteristics of self-organization, dynamism, reliability and data-centricity, which make them applicable to places that are inaccessible to personnel[1], such as battlefields and deserts. Therefore, the potential applications of WSNs include: geophysical surveillance (seismic activity), precision agriculture (soil management), habitat surveillance (tracking animal herds), tracking battlefield targets, disaster relief networks, etc. 2 Security Analysis Early research focused on the development of new network protocols. The new protocols have stricter performance requirements than other ad-hoc networks, including energy saving, self-organization, and measurability of a large number of nodes. However, most applications of sensor networks face serious security problems, including eavesdropping, sensor data forgery, denial-of-service attacks and physical compromise of sensor nodes. This makes security issues as important as other sensor performance issues. The following is a specific analysis of network security threats to sensor networks and proposes appropriate solutions to adapt to this new special ad-hoc network classification. I. Routing Security Many sensor network routing protocols are quite simple and do not place security as the main goal. Therefore, these protocols are more vulnerable to attacks than in general ad-hoc networks. Karlof et al. introduced how to attack ad-hoc networks and end-to-end networks, and also introduced sinkhole and HELLO flood attacks. We will briefly introduce these two types of attacks on sensor networks. Sinkhole attacks, based on routing algorithm techniques, attempt to induce almost all data destined for a weakened node, creating a "sinkhole" at the attacker's center. For example, an attacker might deceive or replay false information onto a high-quality route through a weakened node. If the routing protocol uses an end-to-end acknowledgment technique to verify route quality, a powerful laptop-type attacker might supply a high-quality route, providing enough power to reach the destination in a single hop, similar to early rushing attacks. Because sinkhole attacks involve a large number of nodes, they can induce many other attacks that tamper with traffic flow, such as selective forwarding. We should mention that sensor networks are particularly vulnerable to this type of attack due to their unique communication paradigm; all nodes must send sensing data to a receiving node. Therefore, a weakened node can only provide a single high-quality route to the receiving node in order to sense a potentially large number of nodes. Sinkhole attacks are difficult to defend against, especially with integrated routing protocols, combined with data information such as remaining power. In addition, geo-routing protocols are well known for resisting sinkhole attacks because their topology is built on local information and communication, which is naturally addressed by the actual location of the receiving node, making it difficult to induce it to create sinkholes elsewhere. HELLO flood attack - This type of attack sends hello packets, which are required by most routing protocols, to their neighboring nodes. Nodes receiving such packets may assume that they are within range of the sender. Laptop-type attackers can send such packets to all sensor nodes in the network to make them believe that the weakened node belongs to their neighbor. This causes a large number of nodes to send packets to this fictitious neighbor. Several routing protocols in sensor networks, such as Directed Diffustion, LEACH, and TEEN [2], are vulnerable to this type of attack, especially when hello packets contain routing or location information exchanged. A simple way to reduce hello flood attacks is to verify that the link is bidirectional. However, if the attacker has a highly sensitive receiver, a trusted receiving node may only select a limited number of neighboring nodes for each node in order to prevent hello attacks. Solutions: SPINS Security Framework Protocol - SPINS proposes two preferred sensor network security protocol frameworks: SNEP and μTESLA. SNEP achieves encryption through a link encryption function. This technology uses a shared counter between the sender and receiver, establishing a one-time key for the receiver to prevent replay attacks and ensure data freshness. SNEP also uses a message verification code to ensure authentication between both parties and data integrity. μTESLA is an optimized form of TESLA, a new protocol for providing a strictly authenticated broadcast environment. μTESLA requires loose synchronization between the broadcast node and the receiver. INSENS - INSENS is a routing protocol in sensor networks that provides intrusion tolerance by constructing multiple redundant paths between sensor nodes and receiver nodes to bypass intermediate malicious nodes. Additionally, INSENS also limits DoS-type flooding attacks while preventing sinkhole attacks by preventing erroneous routing information or other control information. However, INSENS has several drawbacks, the most important being that the receiver node should be fault-tolerant and should not be isolated from the rest of the network by attackers during rest periods. II. Key Management and Distribution Although "key management" is important in ensuring confidentiality and authentication, it still has many unresolved issues in wireless sensor networks, mainly in the following aspects: Pre-deployment of keys: Before the sensor network is designed and installed, due to the unknown physical topology, the predeployment key is considered as the only practical choice key to be distributed to the corresponding trusted option. However, the traditional key configuration plan is not suitable for wireless sensor networks. The keys installed at each node are either a single task key or a separate set of n-1 keys, privately paired and shared with another. In fact, the capture of all sensor nodes will jeopardize the security of the entire network, because selective key revocation is not possible in sensor capture reconnaissance, and the solution of key distribution in pairs at each sensor node requires storing and loading n-1 keys [3]. When using more than 10,000 sensors, this becomes impractical due to the resource constraints described above. In addition, since direct point-to-point communication is only done between a very small number of neighboring nodes, the private keys shared between all two sensor nodes cannot be reused. Shared Key Discovery: Another challenging problem is that each node needs to discover a neighbor within wireless communication range where it shares at least one key. Therefore, a link exists between two sensor nodes only when they share a key. A good shared key discovery method should not allow an attacker to know the shared key between any two nodes. Road Key Establishment: For any pair of nodes that do not share keys and are connected in a multi-hop manner, a road key needs to be assigned to guarantee secure end-to-end communication. It is important that the road key is shared unpaired with intermediary nodes. Besides these issues, key management in sensor networks faces other important and challenging problems, such as energy-efficient key reconstruction mechanisms when available keys expire, and minimum key establishment latency. Solutions: To overcome the shortcomings of traditional key configuration, the solution essentially addresses the size of the key configured on each node. For example, the probabilistic key-sharing protocol described uses a guaranteed shared key discovery method between every two nodes, sharing a key with a probability of being selected, with only a small number of keys loaded at each sensor node. The latter is arbitrarily derived from a large key pool. However, this protocol has several drawbacks. Due to its reliance on trusted control nodes, the authentication key identifier of each key circle and the corresponding sensor is stored. In addition, the resilience of the basic probabilistic key sharing method is weak against node capture because only one key is shared between every two nodes, making it relatively easy for an attacker to capture a small number of nodes to break a large number of links. To improve the resilience against node capture, a q-synthesis method [4] is proposed, where q keys (q > 1) need to be shared between nodes instead of one key. This method proves its efficiency compared to the basic configuration when the number of nodes is reduced. Another solution is that a shared key can be located in multiple nodes, not just known by two nodes. Therefore, this key cannot encrypt any private messages between two nodes used in the network. So, we propose to strengthen the basic probabilistic method by establishing a proprietary pairing key for the corresponding communication nodes using limit key sharing. Another important research trend is in the field of key management in sensor networks, including new technologies that allow the use of public key cryptography in such environments. Guabtz et al. proposed that proper selection and careful optimization of the encryption algorithms and associated parameters used, as well as low-power design techniques, may make asymmetric encryption feasible in sensor networks. Although this study showed that public-key encryption can achieve an average power consumption of 20 W less than that of the NtruEncrypt cryptosystem [5], we should note that this algorithm has not yet proven its resistance to cryptanalysis. In addition, considering the security level of the algorithm, it does not reflect the real-world scenario of using asymmetric cryptography in sensor networks, because we believe that the use of public-key mechanisms in wireless sensor networks is more complex with a higher level of security than those symmetric key technologies with lower message exchange. III. Data Fusion Security Data aggregation (or data fusion) is a key topic that has emerged in the design and development of wireless sensor networks. In this process, intermediary nodes called "aggregators" collect raw perceived information from sensor nodes, process it locally, and quickly send the results to end users. This important operation fundamentally reduces a considerable amount of data transmitted over the network, thus extending the node's workload, and is the most important design factor for wireless sensor networks [6]. However, this functionality is challenged due to the existence of attack environments. Assertions on the validity of data fusion are proposed for use with duplicate data fusion nodes. These nodes perform data fusion operations as aggregators, but send the results as a Message Verification Code (MAC) to the aggregator instead of sending it to the base [7]. To prove the validity of the fusion result, the aggregator must send the results received by the nodes it is verifying along the planned route to the base. If a depleted aggregator wants to send invalid fusion data, it must forge a proof for the invalid result. The fusion result is verified when n proves from witness m that the result is consistent with the aggregators' result; otherwise, the latter abandons it and the base sends its valid fusion result. We believe that this solution is efficient when the witnesses are trusted enough; otherwise, it requires the use of a voting scheme to obtain an acceptable fusion result. A secure framework based on a fusion collective proof method is proposed to verify that the value given by the aggregators is close to the true value, even if the aggregators and sensor nodes are corrupted. In this method, the aggregator collects data by building a Merkle messy information tree. The aggregator promises to guarantee the use of data provided by the sensors and serves as a statement verified by the base regarding the correctness of the fusion result. 3 Conclusion Wireless sensors, as special ad-hoc networks, have their own characteristics and also put forward new requirements for security. Security is a key issue in the design of a good sensor network. Without sufficient measures to protect confidentiality, privacy, integrity and other attacks, sensor networks cannot be widely used. They can only be implemented in a limited and controlled environment, which will seriously affect the application prospects of sensor networks. This paper systematically summarizes the research carried out at home and abroad from the aspects of the security attacks that WSN may be subjected to and the corresponding defense methods, and provides appropriate solutions, which helps to understand the current progress and status of WSN security research. References: [1] Liang Guowei, Li Changwu, Li Wenjun. A brief analysis of the development of networked intelligent sensing technology. Microcomputer Information, No. 7, 2004. [2] C. Karlof and D. Wagner, “Secure Routing in Wireless Sensor Networks: Attacks and Countermeasure,” 1st IEEE International Workshop on Sensor Network Protocols and Applications,USA, 2003. [3] L. Eschenauer and VD Gligor, “A Key Management Scheme for Distributed Sensor Networks,” CC502, Washington DC, USA, 2002. [4] RD Pietro, L. Mancini, and A. Mci, "Efficient and Resilient Key Discovery based on Pseudo-random Key Pre-deployment," 18th Int'l. Parallel and Distributed Processing Symp., Apr. 2004. [5] W. Du et al., "A Witness-based Approach for Data Fusion Assurance in Wireless Sensor Networks," GLOBECOM '03, 2003. [6] B. Przydatek, D. Song, and A. Perrig, “SIA: Secure Information Aggregation in Sensor Networks,” SenSys03, 2003. [7] SR Madden et al., “Tag: A Tiny Aggregation Service for Ad-hoc Sensor Networks,” OSDI, Dec. 2002.