Worked on the TUM-DSE/doctor-cluster-config repository to enhance security management by implementing targeted SSH key rotation for cluster access. Focused on system administration tasks, the developer updated device authorization by adding a new SSH key for a specific user’s notebook and removing the previous key, thereby enforcing device-based access control. This approach reduced the attack surface and streamlined credential lifecycle management, making it easier to revoke or audit access as needed. All changes were documented to align with existing security policies, supporting compliance and traceability. The work was carried out using Nix and centered on robust access control for sensitive environments.