Managed File Transfer provides a more secure file transfer options. Implementing this requires the use of secured key pairs. The following is a summary of steps and references. Full credit to Mr. Martin Ng. Platform: AWS EC2 running on Ubuntu AMI. References to path may be different, with ISPConfig installed for virtual hosting management. For key generation: https://www.thesecuritybuddy.com/pgp-and-gpg/how-to-generate-gpg-key/ For generating enough entropy at the last step of key generation (need to open another SSH): https://serverfault.com/a/950103 (essentially run ls on root path so that it generates disk operations / entropy) Encrypting and decrypting: https://www.gnupg.org/gph/en/manual/x110.html Passing passphrase in decrypting (simplified as using this --batch --passphrase 'thepassphrase'): https://superuser.com/a/1358025 Note: The ".gnupg" directory should be in the same directory of the PHP files...
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