timelock

Time-lock puzzles are cryptographic algorithms which encrypt data in a way that it's not possible to decrypt encrypted data until a certain amount of time passes. A good explanation of the algorithm: https://www.cs.tufts.edu/comp/116/archive/fall2013/wclarkson.pdf

Note that this program differs from the algorithm described in the original paper in one aspect. Original algorithm:

1. Generates a random key
2. Uses it to encrypt data with a symmetric encryption algorithm
3. Time-locks the key
4. Outputs encrypted data and time-locked key.

This program doesn't use symmetric encryption, it just time-locks the data you give it. You can use gpg --symmetric to symmetrically encrypt whatever data you want with a random numerical password and then use this program to time-lock the password.

Installation

You can use this program on every single machine at any point in the future, because it's built with Nix. First install Nix:

curl --proto '=https' --tlsv1.2 -sSf -L https://install.determinate.systems/nix | sh -s -- install

For more information on installing and uninstalling Nix, you can check https://zero-to-nix.com/start/install.

Download and run the installer:

nix-shell --pure --packages cacert curl \
  -I 'https://github.com/NixOS/nixpkgs/archive/057f9aecfb71c4437d2b27d3323df7f93c010b7e.tar.gz' \
  --command "curl -sSLOf --proto '=https' 'https://github.com/aerbil313/timelock/raw/main/install-timelock.sh'" \
    && chmod +x ./install-timelock.sh \
    && ./install-timelock.sh

Note: It may take a very long time to build the first time you do it, without any visible progress. Be patient. After the installation completes, you should have dtlp and etlp binaries in your current directory.

Usage

Run commands per the below to see their usage:

./etlp -h

./dtlp -h

TODO for the next person who is willing to take the task:

• Make a tutorial.
• Store every X time the non-resolved puzzle in a cache file.
• Combine two programs into one and rename it to "timelock".
• Make an installer.
• More explanatory and clean usage info.
• Decryption progess bar.
• Encrypt from any kind of data, not just text.
• Hour, min, second is asked to the user separately and can be provided separately as command option.
• Option to delete the data automatically from places warned after encryption.
• If possible, shorten the encrypted message.
• Encrypted data formatted in a way that it's possible for someone with no knowledge of the algorihthm can write a program and decrypt it. Ck, a, t, n values are clear and human-readable, along with the link to the paper above. Still supporting copy-pasting to decryption prompt.
• Don't use key as message, use a symmetric encryption algorithm to encrypt the data with the randomly generated key, time-lock the key, and output encrypted data and time-locked key, like the original algorithm.
• Inform me on your improved version (I need especially the feature above.).