# A Communication-Efficient Secure Routing Protocol for IoT Networks +
## 2 Related Works  
There has been a wide range of discussions on routing over the last 20 years. Although MANETs have attracted considerable attention, recent demands for IoT applications have raised practical implementation issues from various viewpoints, such as energy efficiency [22; 23], communications efficiency [24], and security [14]. In this section, we first review the recent research trends related to secure routing protocols. Secure routing protocols can be divided into cryptographic-based methods [9; 10; 11; 12; 14; 15] and trust-based methods [16; 17; 18]. We summarize these approaches here along with their limitations and differences.  
Trust-based methods do not require cryptographic processing, thereby preventing illegal nodes from joining the route while achieving low computational complexity. [PERSON] et al. proposed a trust-based method based on the DSR protocol that prevents packet drops by sharing attacker information within a network [16]. [PERSON] et al. introduced a base station to calculate the trust value to avoid trust tampering at the nodes [17]. Furthermore, [PERSON]. [18] proposed a protocol that considers resource consumption at nodes. By considering network conditions (such as topology, node power consumption, and channel states), this method is able to identify whether a communications failure is due to an actual failure or a node error. Subsequently, if communications are excessively concentrated on a node, an alternative route is selected. However, detecting a trust forgery is difficult when there are many attackers in the network; thus, the security performance of trust-based routing degrades significantly.  
By contrast, a cryptographic-based secure protocol can successfully prevent forgery and tampering with route packets via computational security. [PERSON] et al. proposed a method for secure node authentication by encrypting the medium access control (MAC) address and sending it to a BS [14]. However, a malicious node can join a network via authentication tampering. Black hole attacks can be prevented by using digital signatures to prevent forging and falsification of messages. [PERSON] et al. proposed Secure-AODV (SAODV), incorporating digital signatures and hash chains into AODV to prevent black hole attacks [25]. Authenticated routing for ad hoc networks (ARAN) [10] adds the digital signature and ID of the intermediate nodes to the routing packet to prove that the relay node correctly sent the message. These cryptographic-based methods are theoretically resistant to packet forgeries and tampering. However, because these protocols allow the nodes to append signature information to the relay packet, communication efficiency tends to decrease hop-by-hop. Motivated by this background, [PERSON]. [11] proposed an efficient and secure routing protocol that integrates multiple signatures into a single size by incorporating the aggregate signature into the DSR. This method can reduce the packet length. However, this method (and the related methods presented above) prohibits the intermediate nodes from generating a route reply (RREP) packet to secure the route; thus, the communication efficiency becomes degraded in large-scale networks incorporating IoT systems.  
To the best of our knowledge, there is currently no routing method that achieves both high communication efficiency and security. Therefore, we propose a cryptographic-based routing protocol that achieves both communication efficiency and security performance.