The ethereum 2.0 Medalla testnet has five node clients, but just one of them is being used by the vast majority of nodes.
Despite a week long network crash in August due to a small bug in Prysm, that client is still being used by some 60% of the network.
That’s way more than enough to take the whole thing down as knocking off only 33% of the nodes is sufficient to prevent ethereum 2.0 from finalizing.
Once the network can not finalize, it effectively stops working, something that would cause chaos in a live ethereum network that holds some $11 billion in defi.
The second most popular client is Lighthouse with just 36 nodes out of 155, making it 23% according to our own research based on eth2stats.
If this client goes down there could be problems, but not fully critical problems like were anything to be exploited in Prysm.
Teku has 15 nodes out of 155, less than 10%, with Nimbus at 9 and Lodestar at just 2.
It’s not clear why Teku and Nimbus are not finding much use, but in this testnet we have a Pareto distribution between dominating Prysm and way behind Lighthouse, with then the rest even more behind in network share.
It’s not clear whether there’s anything that can be done about this as if it replicates in the live network, then there would be significant problems temporarily if Prysm nodes are DDoS-ed for example.
These open networks are somewhat easy to DDoS and there’s so many ways to do it, you can’t fully protect from it but you can minimize or even avoid it in bitcoin by not having open connections on your node.
In ethereum 2.0 there’s probably minimization strategies as well, but Prysm nodes are currently nearly twice the amount required to take down the network. Just half of them would be close to enough.
Prysm is working on a method to quickly export your validation to another client, but it’s not too clear whether that is something that can easily be done.
Nor is it too clear whether node operators can effectively be persuaded to maintain a less than 30% share per client.