#https://www.howtoforge.com/tutorial/how-to-encrypt-directories-and-partitions-with-ecryptfs-on-debian/
sudo apt install ecryptfs-utils
sudo mount -t ecryptfs <folder> <folder>

##############output################
Select key type to use for newly created files:
1) tspi
2) passphrase
Selection: <-- 2
Passphrase: <-- Enter a secure password
Select cipher:
1) aes: blocksize = 16; min keysize = 16; max keysize = 32
2) blowfish: blocksize = 8; min keysize = 16; max keysize = 56
3) des3_ede: blocksize = 8; min keysize = 24; max keysize = 24
4) twofish: blocksize = 16; min keysize = 16; max keysize = 32
5) cast6: blocksize = 16; min keysize = 16; max keysize = 32
6) cast5: blocksize = 8; min keysize = 5; max keysize = 16
Selection [aes]: <-- Press ENTER
Select key bytes:
1) 16
2) 32
3) 24
Selection [16]: <-- Press ENTER
Enable plaintext passthrough (y/n) [n]: <-- Press ENTER
Enable filename encryption (y/n) [n]: <-- Press ENTER
Attempting to mount with the following options:
ecryptfs_unlink_sigs
ecryptfs_key_bytes=16
ecryptfs_cipher=aes
ecryptfs_sig=bd28c38da9fc938b
WARNING: Based on the contents of [/root/.ecryptfs/sig-cache.txt],
it looks like you have never mounted with this key
before. This could mean that you have typed your
passphrase wrong.
Would you like to proceed with the mount (yes/no)? : <-- yes
Would you like to append sig [bd28c38da9fc938b] to
[/root/.ecryptfs/sig-cache.txt]
in order to avoid this warning in the future (yes/no)? : <-- yes
Successfully appended new sig to user sig cache file
Mounted eCryptfs