HOWTO : Encrypt/Decrypt BackTrack 5 R2 with USB stick

Credit to : Hak5.org

Step 1 :

To check the device label :

sfdisk -l /dev/sda
sfdisk -l /dev/sdc

*** Where sda is my hard drive and sdc is the USB stick

Step 2 :

To format the following devices with linux format :

fdisk /dev/sda
d
n
p
1
p
w

fdisk /dev/sdc
d
n
p
1
p
w

Step 3 :

dd if=/dev/sdc bs=1 count=64 skip=32 of=/tmp/first.key

cryptsetup -c aes-xts-plain -s 512 luksFormat /dev/sda1 /tmp/first.key

cryptsetup -d /tmp/first.key luksOpen /dev/sda1 mylaptop

ls /dev/mapper

Step 4 :

mkfs.ext2 /dev/sdc1

mkfs.ext4 /dev/mapper/mylaptop

*** Where mylaptop is the label of the device.

Step 5 :

Install BackTrack 5 R2 as usual. However, do not format the partitions. Select /dev/mapper/mylaptop as ext4 and /. Then, select /dev/sdc1 as ext2 and /boot.

After that, make sure the bootloader is installed at /dev/sdc

Step 6 :

Once the installation is completed, select "Continue testing" and do not reboot.

dd if=/dev/sdc bs=1 count=64 skip=32 of=/tmp/second.key

Make sure the keys are different.

sha1sum /tmp/*key

Step 7 :

cryptsetup -d /tmp/first.key luksAddKey /dev/sda1 /tmp/second.key

mkdir /mnt/mylaptop

mount /dev/mapper/mylaptop /mnt/mylaptop/
mount /dev/sdc1 /mnt/mylaptop/boot

chroot /mnt/mylaptop/

mount -t proc proc /proc
mount -t sysfs sys /sys/

Step 8 :

nano /etc/crypttab

blkid /dev/sda1

mylaptop /dev/disk/by-uuid/<UUID Key> none luks

nano /etc/fstab

/dev/sdb1 /boot ext2 defaults 0 2

Step 9 :

After that, boot BackTrack 5 R2 from the USB stick. It will drop to the busybox.

At the busybox, enter the following commands to unlock the partition. You are required to enter these commands on every boot up.

dd if=/dev/sdb bs=1 count=64 skip=32 of=/tmp/mykey.key

cryptsetup -d /tmp/mykey.key luksOpen /dev/sda1 mylaptop

Then press Ctrl-D to continue the boot process.

Step 10 :

After the system is boot up, it is required to create swap file.

dd if=/dev/zero of=/swapfile1 bs=1M count=512

* Where count=512 is 512M

mkswap /swapfile1
chown root:root /swapfile1
chmod 0600 /swapfile1

swapon /swapfile1

nano /etc/fstab

/swapfile1 swap swap defaults 0 0

Then reboot the system.

Remarks :

You are required to enter these commands on every boot up.

dd if=/dev/sdb bs=1 count=64 skip=32 of=/tmp/mykey.key

cryptsetup -d /tmp/mykey.key luksOpen /dev/sda1 mylaptop

See Also : HOWTO : Encrypt/Decrypt BackTrack 5 R2 with Passphrase

That's all! See you.