I have a noob idea and I want to understand where I'm going wrong :)

Say nodes agreed on a block revision limit, say, 6. This would mean that if they see an incoming chain that is longer than the previous longest chain they have seen, they would reject it if it involved changes in blocks further back than 6 blocks ago on their previous longest chain.

If vendors then required 6 confirmations before delivering purchased product, they could be sure that the majority-agreed chain will not be revised to double spend the BTC used to purchase that product. This would protect against a 51% attack.

What am I missing?

1 Answer 1


What am I missing?

What is the length of largest known reorganization in bitcoin?

There have been only two large re-orgs in Bitcoin's history. The first is the value overflow incident in August 2010 that caused a re-org of 53 blocks and the March 12, 2013 fork that caused a re-org of 24 blocks.

There may be a future need for a reorg of more than 6 blocks?

The alternatives may include the forking and fragmentation of Bitcoin, possibly leading to failure.

At the very least, anyone proposing this sort of change ought to be expected to provide a thorough mathematical and statistical analysis of all previous reorgs and how their proposal would have affected outcomes.



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