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Horcrux: immortality for your encrypted backups

Horcrux is a Python script that glues a few well-known, trustworthy tools together for "Voldemort-style" encrypted backups. You can encrypt new files at any time, but decrypting them again requires gathering N of M pieces of the master key. You pick N and M, and hide the pieces wherever you want.

Set up your horcruxes today, and stop worrying about getting hacked or forgetting your password! Back them up in separate locations: put them on CDs or thumbdrives, give them to friends, hide them in pictures or audio files, print them on metal plates in a vault guarded by a dragon. Be creative.

It's free and open source. Tip whatever you think it's worth (links at the bottom). All I ask is during the next bull run, if you suddenly have a scary amount of money, spare a thought for the little project that keeps it from actually being scary!

Tutorial videos

These videos are probably the best entry point if you want to be confident managing your secret keys. They're a little slow (try 1.5X or 2X speed!) but they go all the way from zero to secure encrypted backups and explain everything in detail.

Skip to Developer QuickStart instead if you know your way around the command line and just want to try it fast.

I'm just a normal person. Why do I need that?

It sounds like overkill, but there really is no better way! My opinion is that most normal people will eventually discover a need for something like this as their lives come to depend more and more on passwords.

The problem is that storing digital secrets is tricky because two bad things could happen:

  1. you lose your secret
  2. someone steals your secret

Both are pretty bad if the secret is your master password or some cryptocurrency. And what's worse, being safer from one generally makes you more vulnerable to the other... Wrote your password on paper? Someone might read it. Carefully memorized a long mnemonic passphrase? You might hit your head and forget it, or you might be in a coma.

This scheme is the simplest, most effective way to protect against both risks at once.

It also has several other advantages:

  • You can pick pick how worried you are about each: use higher N (keys needed to decrypt) if you worry more about theft, or higher M (keys total) if you worry more about losing access.

  • The time and effort needed to assemble the pieces offers some protection from being physically robbed, or (much more likely) losing money on impulsive crypto trades.

  • It can be both a backup and a will. Distribute shares to trustees along with a horcrux signed document explaining what you want done when you die.

How does it work?

All the keys are made with one command, like horcrux setup 3 5 my-first-horcruxes. What it does is:

  1. Generate a long random master password and break it into 5 shares (aka horcruxes) using Shamir's secret sharing scheme, with 3 of the 5 required to reconstruct it. You can optionally pick part of the master password yourself to ensure that you trust the randomness.

  2. Generate an encrypt/decrypt GPG keypair and shield the private (decrypt) key with the master password. This makes it possible to make new encrypted files from your day-to-day computing environment using the encrypt key, but then to decrypt them you need access to 3 of the 5 horcruxes.

  3. Generate a separate sign/verify GPG keypair for signing the encrypted files. You can use your own existing GPG key for this instead if you want. It lets your friends/family check that encrypted files are really from you and were transferred correctly, even though they can't decrypt them.

These files are created in the my-first-horcruxes folder:

  • encrypt.key for encrypting secrets (keep this)
  • sign.key for signing secrets (keep this)
  • verify.key for checking signatures (keep + distribute this)
  • decrypt.key for decrypting (keep + distribute this; it's locked with the horcruxes)
  • 5 horcrux-XX.key master password shares, and 5 matching .key.sig signature files (distibute and/or keep them in separate locations)

Now all you have to do is distribute them, encrypt some stuff, and test that you really can bring any 3 horcruxes together to decrypt!

There are also some extra commands to help with distribution: hide to hide a horcrux in a photo or audio file, unhide to get it back, and qrcode to generate a QR code of it, suitable for printing. (NOTE: qrcodes not implemented yet)

Can I trust you?

No. I mean, yes, but there's no way to prove that and you shouldn't rely on it. Instead you should take some common-sense security measures:

  1. Set it up in an isolated environment like TAILS (see below), make sure everything works, then never connect it to the internet again after generating your keys. That way, the only way for anyone to get your master password would be if they already hacked the TAILS random number generator beforehand, or they're physically watching you. Most people don't need to worry about that.

  2. While generating your master password, manually change some characters. This protects against bugs in the system random number generator or me somehow making it generate easy-to-guess passwords. Horcrux will prompt you to do that.

  3. If you can you should read the source code. It's about 400 lines of Python. Alternatively, Horcrux can print out all the commands as it runs them. You could re-run them yourself separately. Then you only have to trust the TAILS + Debian developers. (NOTE: not implemented yet)

The offline environment might seem like too much work, but is necessary if you want to protect something important, like cryptocurrency or highly sensitive documents. Computers get hacked all the time!

Developer QuickStart

Install

You need Nix, but then the rest is easy:

Usage

Might be better viewed in a new tab.

Generic install

Horcrux should work anywhere you can install the following Debian packages or their equivalents:

  • gnupg
  • pwgen
  • python3
  • python3-docopt
  • python3-gnupg
  • ssss
  • steghide
  • qrencode
  • expect
  • unzip

They're easy to get in Debian, Ubuntu, or a similar distro:

 apt install gnupg pwgen python3 python3-docopt python3-gnupg ssss steghide qrencode expect

Once you have the dependencies, clone this repository and check that it works with the included test scripts. It should look something like this:

 git clone https://github.com/jefdaj/horcrux
 cd horcrux
 ./test/test.sh
 running 00-deps.sh... ok
 running 01-help.sh... ok
 running 02-setup.sh... ok
 running 03-sign.sh... ok
 running 04-encrypt.sh... ok
 running 05-verify.sh... ok
 running 06-decrypt.sh... ok
 running 07-hide.sh... ok
 running 08-unhide.sh... ok
 running 09-autoverify.sh... ok
 running 10-autodecrypt.sh... ok

Note that for some reason you need root access to use steghide. Without that the optional hide and unhide commands won't work and their tests will fail.

TAILS install

I recommend doing everything in TAILS because it's portable, relatively simple to set up, leaves no trace of your keys on disk, and will work on a different computer in the future. You'll need to:

  1. Download and install TAILS on a USB drive. See the site for instructions.

  2. Reboot into TAILS. Click the button to create persistent storage, then Start.

  3. The persistent volume wizard should pop up after the desktop starts. Set a good, memorable password. Then enable at least Persistent Folder, Additional Software, and Dotfiles. Do NOT check Network Connections! You want it to forget your wifi password. The wizard auto-saves, so just close it.

  4. Reboot and unlock your new persistent storage on the Welcome screen. Also set a temporary root password (plus sign at the bottom) so you can install software.

  5. Connect to your wifi in the upper right corner menu.

  6. Open Applications -> Tor Browser and navigate to this site (https://github.com/jefdaj/horcrux). Click Code -> Download ZIP to download the source code. In the next step we'll move it into place and install dependencies.

  7. Open a root terminal (Applications -> System Tools -> Root terminal), put in the temporary root password, and run these commands one at a time. You can copy + paste them from here if you like. When prompted, confirm that you want to make the software persistent.

    apt update
apt install -y gnupg pwgen python3 python3-docopt python3-gnupg ssss steghide qrencode expect unzip
cd /live/persistence/TailsData_unlocked
unzip /home/amnesia/Tor\ Browser/horcrux-*.zip
mv horcrux-* horcrux
chown amnesia:amnesia horcrux -R
mv horcrux/tails/*.desktop Persistent/
mv /home/amnesia/.bashrc dotfiles/
echo 'export PATH=/live/persistence/TailsData_unlocked/horcrux:$PATH' >> dotfiles/.bashrc

    Assuming that all went well, you should now be able to run the test scripts. (See the Generic Install above)

  8. Reboot one more time so you can Disable all networking at the startup screen before generating your real keys. To check that horcrux installed correctly, open a new (non-root) terminal and type horcrux -h. You should see the help message.

  9. This last step is optional, but good if you plan to give copies of TAILS to other people as part of a will. The tails folder in this repo contains two Linux application launcher shortcuts (the .desktop files). You can put them in /home/amnesia/Persistent and use them to do the verify and decrypt operations without any command line knowledge. Just tell your trustees/family/friends to put all the keys and backups together in the same folder, then drag the folder onto one of the .desktop files to do the magic.

Qubes install

Another good option for advanced users is Qubes. You shouldn't install it just for this, but if you use it already then a minimal offline VM (vault) is a reasonable place to keep the Horcrux program along with your sign, encrypt, and (locked) decrypt keys. Simply install the dependencies in the TemplateVM. This setup has the advantage of making it easier to horcrux-encrypt your files, because you don't need to reboot into TAILS each time. It may also work with Qubes Split GPG, although I haven't tried.

Basic setup

After checking that the test scripts work, play around with the commands:

  1. Generate some keys with a command like horcrux setup N M my-first-horcruxes, where "N of M" is how many horcruxes you want to be required to unlock everything out of how many total. For example 2 of 3, 3 of 5, or 7 of 10 would be reasonable choices. Remember to delete these practice ones when ready to do it for real, so you can't mix them up.

  2. Practice moving your horcrux keys to separate media, encrypting things, destroying the originals, and putting the horcruxes back together to recreate the originals. Convince yourself it will definitely work when you need it.

  3. Delete the original secrets! This is emotionally hard, but repeating step 2 a few times should help. You might want to wait a week or a month, then make sure your horcruxes still work, then finally delete the original secrets.

You can also repeat these steps to make a "Horcrux live USB" for friends and family. Copy the verify.desktop and decrypt.desktop launchers into their ~/Persistent so they can drag the backup folder onto them to verify and/or decrypt the backups, depending which keys you give them. Of course, you can give them just the horcrux itself if you plan to be around to decrypt it.

Donations

I accept donations of any other crypto too! Just email or open an issue.

Coin Address
Bitcoin 1PEhbpXYrtwK4JWfrrhCcWt4sgxijc9CT7
Bitcoin Cash 1EybRPMNwW5EnP7rGtMGnP1BZzn284b2vi
Cardano addr1q8f075hufxmvvvtwr9uu55scuvh84kquh77rxqmu857ss3qhuujld7ljmrd7nh050w2gczxvk66c7jrhvysj27vgufms5vx2wp
Ethereum 0x814CE5693C2250fcc3ef26f13C22112B32b32943
Litecoin MBBgdzToFS3aY2yrqu4F42RLvoo8iw6cNF