## 6 Comparison and Discussion  
In the literature, numerous research works have been done on IoT and LPWAN at large. However, there have been relatively limited research works focusing on LPWAN security assessment and attack countermeasures. Most of the LPWAN security research works in the literature focused mainly on analyzing the threats and vulnerabilities of LPWAN technologies with less details on proffering possible solutions to the menaces. In Table 2, we summarized some recent research works that discuss the different LPWAN security threats and the solutions proposed. Table 2 presents the comparison of different LPWAN security challenges discussed by various authors in the literature, the methodology deployed by the authors, their strengths and drawbacks are briefly summarized. Most of the solutions highlighted by the various authors in the table have not been experimentally tested to prove their feasibility in real world attack mitigation. Thus, there is still a wide gap in building effective security framework for LPWANs.  
\begin{table}
\begin{tabular}{p{56.9 pt} p{113.8 pt} p{113.8 pt} p{113.8 pt}} \hline \hline
**Refs.** & **Security Threat(s) Addressed** & **Security Requirements** & **Brief Summary of Approach, Highlight Strength and Limitation** \\ \hline
[62] & Problem of key updates & Confidentiality & Proposed the use of a root key update scheme for reinforcing the session key derivation security. \\  & & & **Strength:** Requires fewer computing resources. Offers suitable randomness of the generated updated key. \\  & & & For the blockage of repeated transmission of packets, a frame counter which involves two different 128-bit AES keys: AppSKey and NwkSKey for upstream and downstream messages exchange was proposed. & \\  & & & A trusted third-party PKI (scheme) was proposed. & \\  & & & **Strength:** Strong key management and distribution. \\  & & & **Limitation:** High computation involved due to the involvement of a third party. Complex join produce. \\  & & & Several AES-128 encryption keys at the network layer and application layer was used for data authentication and privacy respectively. \\  & & & Ephemeral Diffie-Hellman Over COSE (EDHOC) approach that uses a cryptographic material derived at the application layer for updating LoRaWAN session keys is proposed. & \\  & & & **Strength:** Low computational cost and flexibility in session keys updates. & \\  & & & Proposed a dual key-based activation scheme for LoRaWAN security solution. NwkSKey and AppSKey was used in performing initial join procedure and the session key created in the initial join procedure is used for second join procedure. & \\  & & & **Strength:** No third party involved. Secured connectivity between end devices and application server. & \\  & & & **Limitation:** Perfect forward secrecy is not guaranteed. & \\  & & & Proposed a shuffling method to prevent bit flipping attack. & \\  & & & **Strength:** Prevent attackers from identifying positions of message field from bit-flipping attacks. & \\  & & & **Limitation:** Not suitable for devices with low power and low resources. & \\  & & & Proposed a security protocol that comprises of a dual option (default option and security enhanced option) for preventing intruders from breaking the end-to-end security between a device and the application server. & \\  & & & **Strength:** Supports mutual authentication, secret key exchange, perfect forward secrecy and end-to-end security. & \\ \hline \hline \end{tabular}
\end{table}
Table 2: A Comparison of Different Scheme Employed to Prevent LPWAN Attack.