I'm a researcher studying the security, fairness, and privacy concerns within machine learning. My goal is to better understand machine learning and intelligent systems, in order to improve their safety and broaden their utility. I mainly have expertise in machine learning and deep learning, cyber security and trust, and secure systems and protocols.
Publications
- C. Lewis, N. Li, and V. Varadharajan, "Targeted context based attacks on trust management systems in IoT," IEEE Internet of Things Journal, vol. 10, no. 14, pp. 12 186–12 203, 2023. doi: 10.1109/JIOT.2023.3245605. [pdf] [code]
- C. Lewis, V. Varadharajan, and N. Noman, "Attacks against federated learning defense systems and their mitigation," Journal of Machine Learning Research, vol. 24, no. 30, pp. 1–50, 2023. [pdf] [code]
- C. Lewis, V. Varadharajan, N. Noman, and U. Tupakula, "Ensuring fairness and gradient privacy in personalized heterogeneous federated learning," ACM Transactions on Intelligent Systems and Technology, vol. 15, no. 3, 2024, issn: 2157-6904. doi: 10.1145/3652613. [pdf] [code]
- C. Lewis, V. Varadharajan, N. Noman, U. Tupakula, and N. Li, "Mitigation of gradient inversion attacks in federated learning with private adaptive optimization," in IEEE 44th International Conference on Distributed Computing Systems (ICDCS), 2024, pp. 833–845. doi: 10.1109/ICDCS60910.2024.00082. [pdf] [code]
- C. Lewis, V. Varadharajan, N. Noman, U. Tupakula, and K. K. Karmakar, "Achieving robustness and dropout fairness with hierarchical federated learning in smart grid infrastructures," ACM Transactions on Cyber-Physical Systems, 2025, Just accepted. [pdf] [code]
- C. Wang, J. Xu, J. Chen, V. Varadharajan, and C. Lewis, "PrivESD: A Privacy-Preserving Cloud-Edge Collaborative Logistic Regression Model over Encrypted Streaming Data," in IEEE Transactions on Dependable and Secure Computing, doi: 10.1109/TDSC.2025.3617797. [pdf]
Teaching
The University of Newcastle, Australia
- COMP6360 – Data Security – Course Content Development – 2019
- SENG2250 – System and Network Security – Teaching Assistance and Marking – 2019-2024
- SENG1110 – Introduction to Object Oriented Programming – Teaching Assistance and Marking, 2020-2023
- SENG2200 – Programming Languages and Paradigms – Teaching Assistance – 2022
- COMP3350 – Advanced Database – Teaching Assistance and Marking – 2021-2023
- COMP3260 – Data Security – Teaching Assistance and Marking – 2023-2024
- STAT1100 – Data Wrangling and Visualisation – Teaching Assistance, Marking, and Course Content Development – 2023-2024
- STAT2110 – Engineering Statistics – Teaching Assistance and Marking – 2023
- SENG4500 – Network and Distributed Computing – Teaching Assistance and Marking – 2023
- INFT3060 – Cloud Computing – Marking – 2025