A European Union official is preparing a confidential report about a diplomatic crisis and must share it with a colleague in an EU delegation abroad. The report contains personal data of third-country citizens and requires a digital signature that guarantees the integrity of the document and the identity of the signer. According to the legal and operational framework of the European Union, which is the most appropriate technical and legal solution to ensure the authenticity and integrity of this digital document, recognizing its validity in all Member States?