LibreCrypt

root@cc ~ # cryptsetup luksFormat /dev/sdb1

WARNING!
========
This will overwrite data on /dev/sdb1 irrevocably.

Are you sure? (Type uppercase yes): YES
Enter passphrase:
Verify passphrase:
root@cc ~ # cryptsetup luksOpen /dev/sdb1 pen
Enter passphrase for /dev/sdb1:
root@cc ~ # mkfs.vfat -F 32 /dev/mapper/pen
mkfs.fat 3.0.28 (2015-05-16)
unable to get drive geometry, using default 255/63
root@cc ~ # mount /dev/mapper/pen /mnt/C
root@cc ~ # echo Proba > /mnt/C/proba.txt
root@cc ~ # cat /mnt/C/proba.txt
Proba
root@cc ~ # umount /mnt/C
root@cc ~ # cryptsetup luksClose pen
root@cc ~ # cryptsetup luksOpen /dev/sdb1 pen
Enter passphrase for /dev/sdb1:
root@cc ~ # mount /dev/mapper/pen /mnt/C
root@cc ~ # cat /mnt/C/proba.txt
Proba

Bovites#
root@cc ~ # lsblk -f /dev/sdb
NAME    FSTYPE      LABEL       UUID                                 MOUNTPOINT
sdb     iso9660     ARCH_201507 2015-07-01-16-59-27-00
├─sdb1  crypto_LUKS ARCH_201507 6a455308-689b-4c8f-88e2-b196a1617a85
│ └─pen vfat                    BF76-0D0F                            /mnt/C
└─sdb2  iso9660     ARCH_201508 2015-08-01-07-07-00-00