Nested Full disk encryption guide for PLAIN encrypttion (Arch Linux):

The guide applies to plain encryption of entire disks (NOT Luks). Using Arch wiki https://wiki.archlinux.org/title/Dm-crypt/Encrypting_an_entire_system#Plain_dm-crypt and making logical adjustments to the procedure template below works well.

The only problem arises when you try to replace "crypto" to "crypto2" in etc/initcpio/hooks/encrypt2 file. That is because it contains "cryptopt" and "cryptoptions" strings that should not be modified. Otherwise, it's smooth sailing.

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Nested Full disk encryption guide (Arch Linux)

Disclamer: This is intended to be used as a reference side by side with the arch linux installation guide on the wiki

Recognized benefits:

[*] Encryption Redundancy

[*] Multiple keys must be entered to decrypt a single partition

[*] Decreased chance of data recovery via cold boot attacks # aka 3 is more difficiult to recover than 1

[*] Decreased chance of shoulder surfing

1. Run "fdisk -l" and identify what partiton you want to encrypt, for me it was /dev/sda3 because I'm going to have an nested encrypted LVM setup

2. encrypt the initial partition:

cryptsetup luksFormat -s 512 -h sha512 -c aes-xts-plain64 /dev/sda3

3. open the encrypted partition

cryptsetup open /dev/sda3 crypta

4. encrypt the unencrypted version of the encrypted partition (nesting)

cryptsetup luksFormat -s 512 -h sha512 -c serpent-xts-plain64 /dev/mapper/crypta

5. open the encrypted parititon /dev/mapper/crypta

cryptsetup open /dev/mapper/crypta cryptb

5. encrypt the unencrypted partiton (cryptb)

crypsetup luksFormat -s 512 -h sha512 -c twohfish-xts-plain64 luksFormat /dev/mapper/cryptb

6. open the encrypted parition /dev/mapper/cryptb

cryptsetup open /dev/mapper/cryptb cryptc

7. now you can do what I did if you want which is to create an lvm inside the nested encryption like so

pvcreate /dev/mapper/cryptc # make it a physical volume

vgcreate VolGroup /dev/mapper/cryptc # create volume group

8. Create all the logical volumes

lvcreate -L 10G VolGroup -n tmp

lvcreate -L 15G VolGroup -n root

lvcreate -L 50G VolGroup -n usr

lvcreate -L 25G VolGroup -n var

lvcreate -L 16G VolGroup -n swap

lvcreate -L 25G VolGroup -n home

lvcreate -l 100%FREE VolGroup -n data

9. format the logical volumes with filesystems

mkfs.ext4 /dev/mapper/VolGroup-root

mkfs.ext4 /dev/mapper/VolGroup-home

etc....

10. mount the logical volumes, install the base packages, and chroot into the new systems root directory

11. Create multiple encrypt hooks

cp /usr/lib/initcpio/install/encrypt /etc/initcpio/install/encrypt2

cp /usr/lib/initcpio/hooks/encrypt /etc/initcpio/hooks/encrypt2

cp /usr/lib/initcpio/install/encrypt /etc/initcpio/install/encrypt3

cp /usr/lib/initcpio/hooks/encrypt /etc/initcpio/hooks/encrypt3

sed -i "s/cryptdevice/cryptdevice2/" /etc/initcpio/hooks/encrypt2

sed -i "s/cryptkey/cryptkey2/" /etc/initcpio/hooks/encrypt2

12. edit /etc/mkinitcpio.conf and add "encrypt encrypt2 encrypt3" to the HOOKS=(... Line

13. Generate the new kernel image with "mkinitcpio -p <kernel package" for me its "mkinitcpio -p linux-hardened"

edit "/etc/default/grub" and add the following to the "GRUB_CMDLINE_LINUX="" line so it looks like this:

GRUB_CMDLINE_LINUX="cryptdevice=/dev/sda3:crypta cryptdevice2=/dev/mapper/crypta:cryptb cryptdevice3=/dev/mapper/cryptb:cryptc"

14. Generate the grub configuration file with "grub-mkconfig -o /boot/grub/grub.cfg"