# Security Issues in IoT-Based Wireless Sensor Networks: Classifications and Solutions
## 3 Security Protection Schemes
### Routing Security Protocol Schemes  
Routing security includes two aspects: secure routing and secure data forwarding. In secure routing, nodes are required to cooperate to share accurate routing information, and to keep the network connected efficiently. Secure data forwarding of data packets must be protected from tampering, dropping, or alteration by any unauthorized party. Many routing protocols are specifically designed for WSNs that can be divided into three types according to the network structure: plane-based routing, hierarchy-based routing, and location-based routing [73].  
SPINS (Security Protocols for Sensor Networks) is a set of security protocols optimized for WSNs [74]. It provides component protocols including SNEP (Secure Network Encryption Protocol) and uTESLA (micro-Timed Efficient Stream Loss-tolerant Authentication). SNEP is a symmetric encryption (RC5)-based protocol for data confidentiality and authentication, suitable for resource-constrained WSNs. It is effective against replay, eavesdropping, and spoofing attacks. The uTESLA protocol provides an authenticated broadcast protocol, which is an important mechanism for WSNs. uTESLA allows a node to authenticate broadcasting packets received from another node. Authenticity is guaranteed based on keys revealed at each time frame. This helps to prevent spoofing attacks since only the nodes holding valid keys can generate authentic messages. However, the limitation of uTESLA is that it requires authentication time before being accepted, which causes latency and requires large memory to store unauthenticated packets. To solve this problem, the multi-level key chain method was proposed by the authors in [75]. In this method, instead of sending uTESLA parameters via unicast, the authors used a multi-level key chain to distribute the necessary parameters to the network nodes in advance.  
In [65], [PERSON] proposed a directed diffusion extension to the protocol that provides secure multicast functionality. The logical key hierarchy and extension mechanism for WSN (LKHW) ensures efficiency in routing and security. However, this method does not provide a data authentication. In addition, the LEAP protocol [66] uses a one-way key chain for one-hop broadcast authentication. When a node needs to send a message, the next authentication key in the key chain is attached to the message. The authenticated keys are revealed in reverse order of the order in which they are generated. A receiving neighbor node can verify the message based on the received authenticated key.  
Secure routing protocols provide secure routing and ensure trust in data forwarding. Protocols such as SPINS (including SNEP and uTESLA) are effective against eavesdropping, spoofing, and replay attacks, while LEAP supports multi-level routing with one-hop broadcast authentication. Some protocols are suitable for resource-constrained network nodes (SPINS uses RC5 symmetric encryption with low computational and communication resource requirements). In addition, multiple routing architectures can be applied for scaling and layering, so that the protocol can be designed to suit the requirements of a specific application.  
However, some protocols are not suitable for real-time WSN-IoT applications due to authentication latency (uTESLA requires waiting for key disclosure after a certain time before authentication can be performed). In addition, unauthenticated packets will be temporarily cached at sensor nodes, which greatly affects the operation of large-scale and high-traffic networks.