Demonstration Of “Attack Blocks” On Bitcoin’s Signet Test Network

In two days, on Wednesday April 7th, a handful of Bitcoin Core developers are going to be doing a demonstration of “attack blocks” designed to take an inordinate amount of time to verify on Signet.

The demonstration will take place at 10 AM EST (2 PM UTC). Anyone who wishes to participate can run Bitcoin Core node on Signet and watch the blocks be mined and processed by their node in real-time.

Instructions can be found here to spin up a node and follow along (including how to check your node’s logs to see the verification times for the attack blocks).

The demonstration is not going to show the worst case of the attack (the script and transaction structure required has not been publicly revealed to not give malicious actors even more information about the attack), but it will produce blocks that take orders of magnitude more time to verify than your average block.

The aim of the demonstration is to show users the severity of one of the four severe consensus vulnerabilities that the Great Consensus Cleanup aims to address with BIP 54.

Two more demonstrations will take place at 6 PM EST (10 PM UTC) on April 8th, and at 5 AM EST (9 AM UTC) on April 9th, to allow for Bitcoin users in different global timezones to directly participate as well.

The Signet blockchain is currently at around 32-33 GB, so if you have any device with ample storage space, go ahead and spin up a Signet node to participate.

For your awareness the following software patch was quickly put together for this demonstration and not audited thoroughly (though it is just a basic terminal based-GUI). If you are spinning up a brand new Signet node just for this demonstration on a machine without any funds on it, you should be fine even if you are the paranoid type like me.

For those who don’t want to just poke at log files, AJ Towns provided a patch to the “bitcoin-tui” project, a Terminal based GUI for Bitcoin Core to display the attack blocks during the demonstration. The project creator is working on a proper release in time for the demonstration, but you can also compile it yourself.

Run these commands on Linux (git commands will work on other OSes, and you should be able to find the equivalent CLI commands for your OS easily online):

git clone https://github.com/ajtowns/bitcoin-tui.git

cd bitcoin-tui

git switch 202604-bip54blocks

From there you should be able to just follow the build instructions at the repository here. After compiling, make sure your bitcoind has “server=1” set in the config file, and start up bitcoin-tui. You should find a “Slow Blocks” tab on the right of the top bar.