In the context of the European Union's Common Security and Defence Policy (CSDP), the EU Directorate-General for External Affairs (EEAS) coordinates cybersecurity missions to protect critical infrastructure during a peacekeeping operation in a hostile environment. The operations team must implement technical measures to ensure the integrity of intelligence data and confidentiality of internal communications against threats from both state and non-state actors. Based on the fundamental principles of cybersecurity and the EU's data protection frameworks, which of the following technical measures represents the most robust and specific implementation to ensure that data are not modified or accessed improperly during transmission and storage, while also meeting the information security requirements of EU international operations?