An EU agent responsible for managing confidential data of the Common Foreign and Security Policy (CFSP) needs to transfer a sensitive file containing classified information from the Union to a colleague in an EU delegation based in third-country territory. The agent must ensure that the process strictly complies with data security principles and the EU Cybersecurity Framework, without violating personal data protection rules if EU citizens' data are included. Which of the following actions represents the most robust cybersecurity measure and in line with EU standards for this specific scenario?