How to make a USB linux live system + Public partition + Private encrypted partition
Take a USB key with no important data on it.
Plug it in. And format it in FAT32.
Download a Linux live distribution, for example :
Verify the authenticity of your ISO image:
Use UnetBootin to write the iso of the linux mint to your usb key (/dev/sdb1).
Now reboot on your Live system.
Open gparted, to edit the partitions.
Resize the first and only partition to 5g.
Make a second one of half the rest in FAT32 also.
Make a third one with the rest unformatted.
Now open "Disks" (the disks utility in linux mint), select the third partition, and choose to format it into LUKS+ext4.
now type your passphrase.
type it again.
You now have a USB key to boot on a fresh clean Linux, with a Public partition for sharing files accross devices and an encrypted partition for your secrets.
Do not connect to the internet with it and you should have a clean
Do not type your passphrase to decrypt your Private Encrypted Partition on another system than the live USB key system.