The bitcoin cash network can be split in half for <$1M due to the 10-block rolling checkpoint

The current value of daily block rewards is $138,947.8 USD and the hash rate is 0.95Ehash/s (source).
What the attacker needs is ~1.5-2Ehash/s for a few hours, which should be possible to rent for <$1M.

Preparation: connect to as many nodes as possible, in the same manner that reizu used to double spend on BSV.

The attack: starting from block X, mine 11 blocks in parallel to the 'true' chain and keep them secret. Then, mine on the public chain until we know a (second) valid parallel chain with 11 blocks after X before the public network (it can include blocks mined by others).

Now, release one chain to half of the nodes and another to the other half. The network will permanently split because block X+1 is going to be buried under 10 blocks on both chains.

Ideally, the attack would split the hash rate in half, so subsequent attack on one of the split networks would be much easier.

This is much more dangerous than a simple 51% attack, because the defense against a 51% attack is to increase the number of confirmations. This attack would require manual intervention to fix on at least half of the nodes.

submitted by /u/nootropicat
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source https://www.reddit.com/r/btc/comments/a6hkwy/the_bitcoin_cash_network_can_be_split_in_half_for/