LUKS

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LUKS encryption

Getting Started

See Archwiki: dm-crypt/Device encryption.

Install cryptsetup

sudo apt install cryptsetup

Encrypting a device

# Examples
DEVICE=/dev/sda
NAME=arr1

# Setup encryption
cryptsetup -v --type luks2 --cipher aes-xts-plain64 --key-size 512 --hash sha512 \
           --iter-time 5000 --use-urandom --verify-passphrase luksFormat "${DEVICE}"

# Open encrypted drive to /dev/mapper/$NAME
cryptsetup open "${DEVICE}" "${NAME}"

# Create a partition
mkfs.btrfs /dev/mapper/${NAME}
mount -t btrfs /dev/mapper/${NAME} /media/${NAME}

# Fill the drive to overwrite any existing raw data (optional)
dd if=/dev/zero of=/media/$NAME/file status=progress

Mounting

# Open the encrypted drive
cryptsetup open "${DEVICE}" "${NAME}"
# Mount your partition
mount -t btrfs /dev/mapper/${NAME} "${MOUNT_LOCATION}"

Unmounting

# Unmount your partition
umount "${MOUNT_LOCATION}"
# Close the decrypted drive
cryptsetup close ${NAME}

Encrpytion Options

  • You can see defaults using cryptsetup --help.
  • --type options
    • luks defaults to luks1 on cryptsetup < 2.1.0, luks2 on cryptsetup >= 2.1.0
    • luks1 is the standard version of LUKS.
    • luks2 is a new version released in Dec 2017. Older versions of Grub (before 2.06 or June 2020) do not support booting from LUKS2.
    • plain is dm-crypt plain mode. Avoid this unless you know what you're doing.
    • loopaes Avoid this as well.
    • tcrypt Use this for mounting older truecrypt volumes.
  • --iter-time dynamically determines the number of iterations used to hash your password. The number of iterations is determined when creating the luks key. E.g. 5000 means hash for 5 seconds worth of iterations on your particular CPU. You can see the number of iterations for each key with cryptsetup luksDump <device>.
defaults

defaults on Ubuntu 18.04

Default compiled-in device cipher parameters:
	loop-AES: aes, Key 256 bits
	plain: aes-cbc-essiv:sha256, Key: 256 bits, Password hashing: ripemd160
	LUKS1: aes-xts-plain64, Key: 256 bits, LUKS header hashing: sha256, RNG: /dev/urandom

Benchmark

cryptsetup benchmark
Example Output (i7-12700K)
# Tests are approximate using memory only (no storage IO).
PBKDF2-sha1      3057072 iterations per second for 256-bit key
PBKDF2-sha256    6452775 iterations per second for 256-bit key
PBKDF2-sha512    2432890 iterations per second for 256-bit key
PBKDF2-ripemd160 1289761 iterations per second for 256-bit key
PBKDF2-whirlpool 1148495 iterations per second for 256-bit key
argon2i      13 iterations, 1048576 memory, 4 parallel threads (CPUs) for 256-bit key (requested 2000 ms time)
argon2id     13 iterations, 1048576 memory, 4 parallel threads (CPUs) for 256-bit key (requested 2000 ms time)
#     Algorithm |       Key |      Encryption |      Decryption
        aes-cbc        128b      1976.6 MiB/s      7781.1 MiB/s
    serpent-cbc        128b       136.8 MiB/s       993.0 MiB/s
    twofish-cbc        128b       291.3 MiB/s       646.8 MiB/s
        aes-cbc        256b      1507.6 MiB/s      6406.3 MiB/s
    serpent-cbc        256b       138.2 MiB/s       984.0 MiB/s
    twofish-cbc        256b       295.3 MiB/s       647.1 MiB/s
        aes-xts        256b      6021.9 MiB/s      5909.9 MiB/s
    serpent-xts        256b       855.7 MiB/s       887.4 MiB/s
    twofish-xts        256b       597.8 MiB/s       608.0 MiB/s
        aes-xts        512b      5521.2 MiB/s      5505.7 MiB/s
    serpent-xts        512b       870.2 MiB/s       897.9 MiB/s
    twofish-xts        512b       602.9 MiB/s       607.1 MiB/s

Adiantum

If you're running a device which does not support hardware accelerated AES instructions (e.g. Raspberry Pi), you may be interested in Adiantum[1].
Adiantum is an encryption mode by Google which uses ChaCha12 for block encryption. It is included in Linux kernel v5.0.

Creation
cryptsetup -v --type luks2 --cipher xchacha12,aes-adiantum --sector-size 4096 \
           --key-size 256 --hash sha512 --iter-time 5000 --use-urandom \
           --verify-passphrase luksFormat <device>
Benchmark[2]
cryptsetup benchmark -c xchacha12,aes-adiantum -s 512

Scripts

mount_drives.sh
#!/bin/bash

function mount_luks {
    local fstype=$1
    local device=$2
    local name=$3
    local mountpoint=$4
    if [ ! -b /dev/mapper/"$name" ]
    then
        sudo cryptsetup open "$device" "$name"
    fi
    sudo mkdir -p "$mountpoint"
    sudo mount -t $fstype /dev/mapper/"$name" "$mountpoint"
}

mount_luks btrfs /dev/disk/by-id/<drive> lukscrypt1 /media/lukscrypt1
unmount_drives.sh
#!/bin/bash

function unmount_luks {
    local name=$1
    local mountlocation=$2
    sudo umount "$mountlocation" && \
    sudo rm -r "$mountlocation"
    sudo cryptsetup close "$name"
}

unmount_luks lukscrypt1 /media/lukscrypt1

Resources

References