Avatar
Nice and Kind Vic 2y ago

Theoretical that could happen...

You run a bitcoin node and have Bitcoin. Your last transaction was over 2016 blocks ago. You have friends that regularly transact more often, some in the past day (144 blocks for simplicity).

Unbeknownst to all, a separate chain has been being mined in secret based on 1000 blocks ago (about a week). It becomes the active chain having the most work performed. Your funds predate this and are entirely safe. Some of your friends find that coins they had received on the previously valid chain have been returned to the sender thus lowering their balance.

As unlikely as this seems, it is possible and you should think through how youd react as well as how to push out the inevitable noise

Do you now wait for 1000 confirmations before considering safely received?

As a node runner do you reject the new tip? Do you keep tabs on bitcoin-cli getchaintips

As a miner, do you pull out of mining pools or create new ones? Do you wonder if some of the hash of the pool was being redirected at the other chain? Do you use stratumv2?

If 1000 blocks is too many what if it was 5?

Reply to this note

Please Login to reply.

Discussion

de
nobody 2y ago

How would a secret chain even get 1000 blocks ahead? There's zero probability of this happening over that long of a period of time while there's almost 400 exahash behind the main Bitcoin chain. The compute and energy just doesn't exist in the world to do that.

de
nobody 2y ago

To you final question the answer is "just wait a while" because 6 confirmations is when that feasibility becomes so highly unlikely that it's not worth worrying over.

Avatar
a_priori 2y ago

Sort of unrelated, but do you happen to know why Liquid peg ins take 102 confirmations? Are they trying to get the probability of a reorg to ~0%?

Avatar
Nice and Kind Vic 2y ago

I think this actually could be related, but may piggyback the Bitcoin coinbase output that cant be spent for 100 confirmations. For example if a miner pegged into Liquid using their coinbase then that address (the peg in) couldnt be spent for 100 more blocks. Does make me curious if theres another reason

de
nobody 2y ago

I know next to nothing about Liquid, sorry.

Avatar
Nice and Kind Vic 2y ago

I agree it goes against standard game theory.

Bitcoin is still not using enough global energy to prevent this from happening. The likelihood of this happening is very tiny, but in general contingent on production of mining units and having a decent idea on where those units have shipped and active

Assume an unknown pool has previously participated in known pools but gradually retracted their hash and focused on this shadow chain specifically to cause disruption. This would of course require collusion with a state actor that can fund this type of waste for a >50% of global hash to catch and exceed the active chain.

de
nobody 2y ago

The incentives just don't make sense to do that though. If you have enough energy and hardware to meaningfully overtake the main chain for a brief time you'd make far more money just mining Bitcoin.

There's no government in the world that would spend billions and billions of dollars to do that. It would also be the biggest advertisement for Bitcoin in it's history. "Governments are so scared of Bitcoin that they'd rather spend tens of billions of dollars to attack it than feed their citizens." Everyone Bitcoiners and non-Bitcoiners would revolt at that kind of waste.

Avatar
Nice and Kind Vic 2y ago

I live in the United States and the government here routinely spends money to wage wars around the world. Cost is not a consideration if the ends are achieved.

If the intent is purely to cause chaos and doubt they could achieve this.

I dont think it would happen, but curious what people think they would do.

For me I would certainly want more block confirmations until the cause/culprit(s) identified. I would also consider it an attack if it was shadow mined and wouldnt be opposed to marking their block as invalid.

de
nobody 2y ago

I live in the states too. People are already in a tizzy about not being able to afford rising rents, grocery bills, and healthcare costs, student debts, etc.

Can you imagine the utter shitstorm it would cause if the US government announced a concerted effort to spend $50billion+ to attack BITCOIN? Lmao it would be epic. There'd be guillotines out in front of the capital within the day.

Avatar
nym 2y ago

In the event of a sudden reorganization of the blockchain, several technical considerations would be warranted, reflecting the described scenario.

Waiting for 1000 confirmations before considering a transaction safely received: This depends on your risk tolerance. Historically, six confirmations have been considered secure, but a reorg of 1000 blocks would certainly challenge this assumption. Depending on the perceived risk of further hidden chain mining, waiting for a larger number of confirmations might be prudent, although 1000 might be excessive and hamper practical usability.

As a node runner, rejecting the new tip and keeping tabs on bitcoin-cli getchaintips: You could technically choose to reject the new chain, but this would place you on a fork that might have less mining power and thus be less secure. Regularly checking chain tips and being aware of the state of the network would be a standard best practice. Depending on your view of the legitimacy of the new chain, you might want to take additional steps, such as manually specifying preferred peers that follow the chain you trust.

As a miner, considering pulling out of mining pools or creating new ones: If you suspect that a mining pool was contributing hash power to the secretly mined chain, you would likely want to reevaluate your participation in that pool. Using Stratum V2, which adds more security and transparency, would be a logical step to ensure that your hash power is being used as you intend. Creating new, trusted pools or joining known trustworthy ones could be an appropriate reaction as well.

If 1000 blocks are too many, what if it was 5?: If the reorganization was only 5 blocks, it would be within the realm of what's occasionally seen on the network (though still rare). In this case, a drastic change in behavior, such as waiting for hundreds of confirmations, might not be warranted. However, it might still prompt a review of the network, mining pools, and other factors to ensure that everything is operating as expected.

Avatar
Nice and Kind Vic 2y ago

I appreciate your responses. Very informative.