Okay So the Linux we are talking about at this time is Kubuntu.
And what we will use for will be luks.
It should work similarly on other’s but not guarantee.

Part ONE – Encrypting usb

1. First make sure you have an access to cryptsetup, if not install it
   

   sudo apt-get install cryptsetup

2. Use gparted or any other partition manager to create your partition.
   The easiest thing will be to erase the drive table and just create one ext4 partition.
3. Now lets see our partition table  ( Find partition by typing lsblk )
4. Let say our partition is sdb1, so let’s create luks encrypted partition there
   

   sudo cryptsetup --verbose --verify-passphrase luksFormat /dev/sdb1

5. Okay now our partition is created but is just partition we need to acces it and setup “format”.
   I’ll call it sdb1 so this should be less confusing for everyone.

   sudo cryptsetup luksOpen /dev/sdb1 sdb1

   The first path is our partition location second is a name that we will refer to

6. Now if you type fdisk -l you should see partition like /dev/mapper/sdb1
   If you see it it’s okay to go to next step.
7. Now we need to prepare partition to do that we will format it as ext4 partition
   

   sudo mkfs.ext4 /dev/mapper/sdb1

8. We will also remove the reserved space as by default the reserved space for ext4 is 5% of total drive.
   And if you’re drive is large that 5% could mean a lot. This is normal done so as normal user you will never run out of space but we do not need this here.

   sudo tune2fs -m 0 /dev/mapper/sdb1

9. We will create an folder in mmt.
   

   mkdir /mnt/drive

10. Now let’s mount the drive
    

    mount /dev/mapper/sdb1 /mnt/drive

11. By default as normal user cant browse the encrypted partition so to fix that.
    And let’s change the ownership of the folder to our local user.

    chown -R user: user /mnt/drive

12. Okay now all is set-up.
    You can check with lsblk if the mounting point of sdb1 is our /mnt/drive.
    And if it is you can throw there text file or something.
13. Now it’s nice to unmount and close the partition. Sometimes it does not work so force it or lazy umount.
    For that use google.

    sudo umount /dev/mapper/sdb1

14. And at the end let’s close the partition
    

    sudo cryptsetup luksClose sdb1

Part One Extra

To make our USB auto mountable we will generate an key and we
will add a key to our partition.With this key we can unlock the partition.
We also can unlock the partition with normal passphrase.
You will have to options one is to skip this part.

And use none as a Keyfile which will prompt the user to enter a password on each startup.
However if your main drive is already encrypted and you have to enter a password anyway.
Just store the key on the encrypted partition ( system drive ), so it will be automatically
mounted after successful boot.

Adding Keyfile to existing luks partition

1.  Let’s assume we act as sudo. And we need to generate a key.
   You can also use any other file you want image video etc.
   Best easiest key will be to just generate RSA key.
   We will call our file   file.key  and we gone create it inside /root directory.

   openssl genrsa -out /root/file.key 4096

2. Now we need to prompt the key into our drive
   

   cryptsetup luksAddKey /dev/sdb1 /root/file.key

   You should be prompt -ed to enter original password

3. Now the disk could be unlocked with passphrase or file. Key

Part two – Auto mount encrypted partition

1. Find the UUID of the drive.
   

   cryptsetup luksUUID /dev/sdb1

   Get the uuid of the drive

2. Now go and edit crypttab
   

   nano /etc/crypttab

3. Add folowing line
   -> if you are not using keyfile ( system will ask during boot for password )

   sdb1 UUID=324234234234234234 none luks

   if you are using keyfile

   sdb1 UUID=324234234234234234 /root/file.key luks

4. Now the partition will be automatically decrypted during the boot if the passphrasse will be entered or if you enter correct key file.
5. Partition is decrypted but not mounted and to fix that we need to add an fstab entry.
   So open fstab

   nano /etc/fstab

   And lets att there this entry

   /dev/mapper/sdb1 /mnt/drive ext4 defaults 0 2