# Design of a Lightweight Cryptographic Scheme for Resource-Constrained Internet of Things Devices
## 3 Block Cipher SLA
### Permutation Layer
\begin{split}\text{S}(\text{x}_{1})&=1+\text{x}_{0}+ \text{x}_{2}+\text{x}_{3}+\text{x}_{0}\text{x}_{1}+\text{x}_{1}\text{x}_{2}+ \text{x}_{1}\text{x}_{3}+\text{x}_{2}\text{x}_{3}+\text{x}_{0}\text{x}_{1}\text {x}_{2}+\text{x}_{0}\text{x}_{2}\text{x}_{3}\\ \text{S}(\text{x}_{2})&=1+\text{x}_{0}+\text{x}_{3}+ \text{x}_{0}\text{x}_{1}+\text{x}_{0}\text{x}_{3}+\text{x}_{2}\text{x}_{3}+ \text{x}_{0}\text{x}_{1}\text{x}_{2}+\text{x}_{0}\text{x}_{1}\text{x}_{3}\\ \text{S}(\text{x}_{3})&=1+\text{x}_{0}+\text{x}_{1}+ \text{x}_{3}+\text{x}_{0}\text{x}_{2}+\text{x}_{0}\text{x}_{3}+\text{x}_{1} \text{x}_{3}+\text{x}_{0}\text{x}_{1}\text{x}_{2}+\text{x}_{0}\text{x}_{1} \text{x}_{3}+\text{x}_{0}\text{x}_{2}\text{x}_{3}+\text{x}_{1}\text{x}_{2} \text{x}_{3}\\ \text{S}(\text{x}_{4})&=1+\text{x}_{1}+\text{x}_{3}+ \text{x}_{1}\text{x}_{2}+\text{x}_{2}\text{x}_{3}+\text{x}_{0}\text{x}_{1} \text{x}_{3}+\text{x}_{0}\text{x}_{2}\text{x}_{3}+\text{x}_{1}\text{x}_{2} \text{x}_{3}\end{split}  \tag{26}\]

These forms show that \(\text{Sbox\_Nibble}\), when compared with others with a maximum algebraic immunity of 2, has an algebraic immunity degree of 3, which is sufficiently high to protect it from higher-order differential attacks. As a result, carrying out algebraic attacks through solving a multivariate algebraic equation system is difficult. The cipher structure has no visible flaws such as the absence of fixpoints/negated-fixpoints. In addition, a low-level cryptographic algorithm with a rising number of fixpoints or negated-fixpoints lacks the required randomness, so it is not considered to be well designed. ## 5 Conclusions

This paper has presented SLA, a lightweight scheme. Because SLA is based on the SP-network, it is faster than the Feistel-based cipher. Additionally, the proposed SLA scheme employs a novel encryption method, including finite field multiplication, to construct nonlinear S-box (confusion layer) and the effective one-to-one matrix linear permutation (diffusion layer), which leads to satisfactory security requirements without losing performance efficiency on both execution time and throughput. We exploited properties related to the nonlinear and linear components to design SP network structure. As we designed the SLA, we researched the minimal numbers of active S-boxes and good S-boxes. We also researched the hamming weight calculation for LAT and DDT entries. The proposed SLA design has achieved a small execution time, high throughput, and high level of security. This makes it suitable for small-scale embedded environments such as RFID tags and wireless sensor nodes. Advanced attacks can be used to examine the SLA scheme further. We expect our results to be applied in other domains as well. Conceptualization, N.I. and J.A. ; Methodology, N.I. and J.A. ; Software, N.I. ; Validation, N.I. and J.A. ; Formal analysis, N.I. and J.A. ; Investigation, J.A. ; Data curation, N.I. ; Writing--original draft, N.I. ; Writing--review & editing, J.A. ; Visualization, J.A. ; Supervision, J.A. All authors have read and agreed to the published version of the manuscript. This PhD study is self-funded with no external funding. **Institutional Review Board Statement**: Reviewed by my PhD supervisor. **Informed Consent Statement**: [PERSON] PhD Supervisor for [PERSON] consent and approve to publish this research output as a requirement for examination of her PhD thesis. **Data Availability Statement**: Contact [PERSON], [EMAIL_ADDRESS]. **Acknowledgments**: The authors would like to express their thanks for the infinite grace of the [PERSON] of essential importance. I solemmly offer my regards to His grace, which enabled peace and harmony for this work. **Conflicts of Interest**: The authors declare no conflict of interest. ## Appendix B Test Vectors

## Appendix C

**Proof of Theorem 1.