ecryptfs

• apt install ecryptfs-utils

• https://www.howtoforge.com/how-to-encrypt-directories-partitions-with-ecryptfs-on-debian-squeeze
• https://wiki.debian.org/TransparentEncryptionForHomeFolder
• https://linux.die.net/man/7/ecryptfs

sudo mount -t ecryptfs -o ecryptfs_cipher=aes, ecryptfs_key_bytes=16, ecryptfs_enable_filename_crypto=n, ecryptfs_passthrough=n /media/mate/SECRET /media/mate/SECRET

• option: key=passphrase:passphrase_passwd_file=/mnt/usb/file.txt

• file.txt

  passphrase_passwd=[passphrase]