# Secure Authentication and Credential Establishment in Narrowband IoT and 5G
## 7 Conclusions and Future Work  
Bootstrapping is critical for the secure authentication and credential establishment in NB-IoT and 4G/5G networks. This paper has proposed the adaptation of lightweight bootstrapping protocols to enable a secondary authentication feature of 5G for constrained IoT devices. In fact, this approach represents the adaptation and evaluation of both PANA and LO-CoAP-EAP, to provide high flexibility and scalability in the bootstrapping process. We adapted two EAP lower layers, i.e., (i) PANATIKI as a IETF standardized EAP lower layer and (ii) LO-CoAP-EAP. The latter is a new EAP lower layer specifically designed for IoT and provides high flexibility and scalability in the bootstrapping process. We have compared their leveraging abilities in NB-IoT and 4G/5G environments. Moreover, this paper has explained how limited IoT devices can bootstrap and establish credentials in real scenarios with a 4G/5G network and an AAA infrastructure. Furthermore, the solution allows for deriving credential keys between a limited IoT device and an external IoT controller to create secure channels for protecting M2M data exchange. To validate the proposal, we have implemented, deployed, and evaluated a pilot testbed with real limited IoT devices as part of the proposed use case of precise agriculture. In this case, real devices are connected via NB-IoT modules to a 4G core network and an AAA infrastructure. The performance results demonstrate that LO-CoAP-EAP is a feasible and efficient solution to be used in NB-IoT and future 5G networks to enable the secondary authentication and the security association of limited IoT devices.  
As future work, we consider the implementation of OSCORE to provide efficient secure end-to-end communication for constrained devices, as well as the inclusion of compression techniques to minimise the payload sizes and the number of messages required for the bootstrapping process. Furthermore, the proposed solution can be employed in other applications (i.e., smart cities and smart factories) where the efficient and secure deployment of NB-IoT devices is crucial. Although we presented payload size and runtime latency as performance indicators, further experiments with different IoT device configurations and requirements shall be considered. New results could suggest the level of fitness of the proposal to each specific use case or scenario, together with modifications that would clearly improve its current design.  
Conceptualization, [PERSON], [PERSON], [PERSON], and A.F.S.; Data curation, [PERSON] and [PERSON]; Funding acquisition, [PERSON] and A.F.S.; Investigation, [PERSON], [PERSON], and [PERSON]; Methodology, [PERSON], [PERSON], and [PERSON]; Implementation & prototyping, [PERSON] and [PERSON]; Writing--original draft, [PERSON], [PERSON], and [PERSON]; Writing--review & editing, [PERSON], [PERSON], [PERSON], and A.F.S. All authors have read and agreed to the published version of the manuscript.  
This work has been partially funded by the H2020 EU ANASTACIA project under Grant Agreement 731558, the H2020 CYSEMA project under Grant Agreement 777455, the H2020 project Fed4 IoT under Grant Agreement 814918, and the H2020 EU Plug-n-Harvest project under Grant Agreement 768735, and the Fundacion Seneca--Agencia de Ciencia y Tecnologia de la Region de Murcia FPI Grant 20751/FPI/18. This work was has also been partially funded  
Figure 7: Authentication process total runtime distribution.  
by ODIN Solutions, S.L., under Doctorado Industrial Grant DI-16-08432 and PEANA UNMU13-2E-2536, which is partially funded by FEDER funds.  
The authors declare no conflict of interest.