Introduction

This repository presents an implementation of a plausibly deniable LUKS header in cryptsetup.

DeLUKS provides most benefits of LUKS and of plausibly deniable encryption. The DeLUKS header is designed to be indistinguishible from random data. This is like Truecrypt header, but with GRUB support, multiple keyslots and (to be implemented) an evolutive protection against brute-forcing.

For system encryption, there is a parrallel project to implement DeLUKS in GRUB Cryptomount: grub-crypto-deluks. See the Wiki: System encryption for instructions.

Beta 0.2 available!

cryptsetup-deluks is leaving the Alpha stage and is now in Beta stage, version 0.2.

Instructions are written for and tested on Ubuntu 16.04 and 18.10.

cryptsetup(-deluks) relies on the kernel dm-crypt (which is very stable) to manage the payload encryption/decryption. Indeed, cryptsetup(-deluks) is just a tool focused on encryption header management. It tells dm-crypt where the payload data is on the disk, gives it the key and encryption settings, and that's all. You can be confident about the "beta" status, at least in terms of encryption.

To upgrade to Beta 0.2 (which contains a major header deniability fix), use the command: cryptsetup deluksUpgrade <disk>. You can backup your header with the command dd if=<deluks_disk> of=<backup_file> bs=512 count=2008, however, this will look suspicious if you don't wipe your backup after the upgrade.

Install : System encryption

Not supported on Ubuntu 19.

Note: To create a deniable bootable system, check "Setup case" instructions below before installing cryptsetup.

Replace libgcrypt11-dev by libgcrypt20-dev in the following command if you get an non-existing package error.

if ! grep "universe" "/etc/apt/sources.list" &>/dev/null; then echo -e "\e[43mEnable universe repository, through software-properties-gtk""\e[0m"; software-properties-gtk &>/dev/null ; else echo "OK"; fi
sudo apt-get install git libgcrypt11-dev libdevmapper-dev libpopt-dev uuid-dev libtool automake autopoint debhelper xsltproc docbook-xsl dpkg-dev lvm2
git clone --depth=1 https://github.com/kriswebdev/cryptsetup-deluks.git
cd cryptsetup-deluks
CRYPTLIBDIR=`dirname $(find /lib -name libcryptsetup.so)`
# Must not be empty:
echo $CRYPTLIBDIR
sudo apt-mark hold *cryptsetup*
./autogen.sh --prefix=/usr --sbindir=/sbin --libdir="$CRYPTLIBDIR"
make
sudo make install

Install : Non-system encryption

This install method avoids messing with your distribution cryptsetup* packages; however, it can't be used for system encryption.

Replace libgcrypt11-dev by libgcrypt20-dev in the following command if you get an non-existing package error.

if ! grep "universe" "/etc/apt/sources.list" &>/dev/null; then echo -e "\e[43mEnable universe repository, through software-properties-gtk""\e[0m"; software-properties-gtk &>/dev/null ; else echo "OK"; fi
sudo apt-get install git libgcrypt11-dev libdevmapper-dev libpopt-dev uuid-dev libtool automake autopoint debhelper xsltproc docbook-xsl dpkg-dev lvm2
git clone --depth=1 https://github.com/kriswebdev/cryptsetup-deluks.git
cd cryptsetup-deluks
./autogen.sh --prefix=/usr
make
sudo ln -s `readlink -f src/cryptsetup` /usr/bin/cryptd
sudo ln -s `readlink -f src/cryptsetup` /usr/bin/cryptsetup
cryptd --help
cryptsetup --help

The last line of cryptsetup help should begin with "DELUKS1". Otherwise, it means you distribution cryptsetup-bin package is installed and takes precedence. If you plan to keep your distribution cryptsetup-bin package, just replace cryptsetup by cryptd in the following instructions.

You can chown -R root:root . the current cryptsetup folder for improved security against software modification.

Run

Help:

cryptsetup --help

List your drives:

gnome-disks &
# or
blkid; lsblk -o NAME,FSTYPE,SIZE,LABEL,MOUNTPOINT

Run as root:

sudo su

Warning: If you are using an SSD with sensitive data already present on it, you should sanitize it using ATA Secure Erase BEFORE wiping the drive with the command below. ATA Secure Erase tries to erase the otherwise unaccessible disk wear-level blocks and bad blocks. ATA Secure Erase is performed using Linux hdparm or using the SSD manufacturer tools, preferably after upgrading the disk firmware.

Wipe your drive with random data, fast:

DISK="sdX"
DISKSIZE=$(</proc/partitions awk '$4=="'"$DISK"'" {print sprintf("%.0f",$3*1024)}')
apt-get install pv
# This will erase all data on DISK!
openssl enc -aes-256-ctr -nosalt \
  -pass pass:"$(dd if=/dev/urandom bs=128 count=1 2>/dev/null | base64)" \
  </dev/zero |
  pv --progress --eta --rate --bytes --size "$DISKSIZE" |
  dd of=/dev/"$DISK" bs=2M

Create:

cryptsetup deluksFormat /dev/sdX
# Debug:
# cryptsetup -v --debug deluksDump /dev/sdX

Open:

cryptsetup open /dev/sdX --type deluks deluks_vol

Close:

cryptsetup close deluks_vol

Setup case: Non-system encryption

This is a simple setup with only one filesystem inside the encrypted volume (no partition table, no LVM). It is used to store data. Please keep in mind that your system keeps logs and tracks of what you do, so if deniability is really your objective, you should consider the system encryption setup case.

First, install cryptsetup, then create and open the DeLUKS volume (see above instructions).

Create & mount the filesystem:

mkfs.ext4 /dev/mapper/deluks_vol
mkdir /mnt/mount_point
# To allow the current user to access the mount_point:
$ sudo chown `id -u -n -r`:`id -g -n -r` /mnt/mount_point
mount /dev/mapper/deluks_vol /mnt/mount_point
...
umount /mnt/mount_point

Setup case: System encryption

See the Wiki: System encryption.

Uninstall

To uninstall and return to your the distribution cryptsetup packages:

sudo apt-mark unhold *cryptsetup*
sudo apt-get install --reinstall --only-upgrade *cryptsetup* 

DeLUKS Features

• QUICK BOOT! At GRUB menu, press c to get into GRUB shell, then cryptomount -x / followed by your password. That's all!
• Plausibly DENIABLE!
  • DeLUKS header and encrypted payload are indistinguishable from random data. "Why is there random data on your unallocated disk space? - I wiped my disk"
  • Bootloader is nothing more than GRUB. If the code is integrated upstream, the setup will even be indistinguishable from mainstream GRUB "Why do you have a bootloader with deniable decryption feature? - Do I? It's the default GRUB."
  • No bootloader password menu. This is the basis of deniability - YOU command the bootloader to ask you for a password, not the other way round. "Look, I just installed this O.S. on my wiped drive, it's GRUB's only menu choice. Where would I hide something?"
  • DeLUKS finds encrypted disks by scanning & trying to mount all unallocated disk space > 2MiB.
  • No poorly secured USB key needed! But you may use one if you really want to. "We didn't find any (1) remote header (2) unencrypted keyfile (3) loosely brute-forcable plain dm-crypt keyfile (choose one) on your USB key."
• LUKS multiple keyslots: You can decrypt a disk with any one of 8 passwords. You can change and revoke the passwords.
• LUKS protection against rainbow table attacks: Master key is encrypted with a salt.
• LUKS slow brute-forcing: User password is encrypted with several hash iterations and a salt.
• LUKS anti-forensic information splitter: Low risk that the master key could be decrypted with a revoked password (protection against damaged disk blocks storing the revoked keyslot).
• Pure dm-crypt, no TrueCrypt.
• No need for Truecrypt-style "hidden partition". Instead, you can create a true partition with a fake O.S. GRUB will by default boot on this fake O.S.

Specifications

TODO. In the meantime, you can take a look at deluks.h.

Basically, only the random-looking salts, master key digest and password-salt-PBKDF2-encrypted key materials are left as-is on disk, like in LUKS header.

These elements are used to generate and verify the master key, using the install default settings and user-provided password.

Once the master key is recovered, the options header is decrypted to get additional information, including the payload encryption settings or the disk identifier (UUID).

Everything else in the header is random data or encrypted.