## 5 Conclusions  
In this research, an energy optimization method with secure routing for IoT heterogeneous WSN applications is proposed. This secure as well as reliable routing protocol gathers data about neighbor nodes at BS, and generates the key and energy-efficient multipath for every node. CHs help in data aggregation and forward them to BS, which continuously monitors nodes for residual energy to choose some new paths and CHs. By using the complexity of multimedia processing and the aggregation process to the CHs side, as well as preventing path loops and path cycles for establishing routes, the integrated implementation of MLRP-HTEEN-UDSP produced a minimum end-to-end delay in suitable data packets and reduced the energy consumption at SNs. We also demonstrated a light-weight distributed key management method for supporting secure communication among nodes. The performance of MLRP-HTEEN-UDSP outperforms the existing ones such as LEACH, CCBRP and PEGASIS in all the performance metrics including end-to-end delay, throughput, energy efficiency, network lifetime and data storage capacity. Future work of the proposed protocol will be extended to the performance analysis in the green IoT environments with an increased network size.  
Conceptualization, Writing--original draft R.N.; Supervision, V.C. and S.B.G.; Writing-original draft and review & editing, K.J. and M.G.; Validation, C.V.; propose the new method or methodology, N.R and S.B.G.; Formal Analysis, Investigation C.O.S.; Resources, S.B.G. and C.O.S.; Software, T.C.M.; Writing--review & editing, T.C.M. All authors have read and agreed to the published version of the manuscript.  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Network** & **Throughput** & **End–End** & **Energy** & **Network** & **Data Storage** \\
**Size** & **Throughput** & **Delay** & **Efficiency** & **Lifetime** & **Capacity** \\ \hline
50 & 52 & 25 & 44 & 55 & 42 \\
75 & 61 & 28 & 52 & 65 & 51 \\
100 & 78 & 32 & 61 & 81 & 68 \\
125 & 82 & 38 & 72 & 85 & 72 \\
150 & 85 & 45 & 75 & 88 & 75 \\ \hline \hline \end{tabular}
\end{table}
Table 7: Overall comparisons of MLRP-HTEEN-UDSP.  
Figure 13: Overall comparison of MLRP-HTEEN-UDSP.  
**Funding:** National Research Development Projects to finance excellence (PFE)-14/2022-2024 granted by the Romanian Ministry of Research and Innovation, this paper was partially supported by UE-FISCDI Romania and MCI through projects AISTOR, FinSESco, CREATE, I-DELTA, DEFRAUIDIFY, Hydro3D, FED4 FIRE--SO-SHARED, AIPLAN--STORABLE, EREMI, NGI-UAV-AGRO and by European Union's Horizon 2020 research and innovation program under grant agreements No. 872172 (TESTBED2) and No. 777996 (SealedGRID).  
**Institutional Review Board Statement:** Not applicable.  
**Informed Consent Statement:** Not applicable.  
**Data Availability Statement:** Data will be shared for review based on the editorial reviewer's request.  
**Acknowledgments:** The work of [PERSON] was supported by the European Social Fund under the project \"Talent Management in Autonomous Vehicle Control Technologies\" (EFOP-3.6.3-VEKOP-16-2017-00001). The publication of C.O.S. was supported by funds from the National Research Development Projects to finance excellence (PFE)-14/2022-2024 granted by the Romanian Ministry of Research and Innovation.  
**Conflicts of Interest:** The authors declare no conflict of interest.