Re: [bitcoin-dev] BIP30 and BIP34 interaction (was Re: [BIP Proposal] Buried Deployments)

[Johnson Lau <jl2012@xbt.hk>]

The fact that some implementations ban an invalid block hash and some do not, suggests that it’s not a pure p2p protocol issue. A pure p2p split should be unified by a bridge node. However, a bridge node is not helpful in this case. Banning an invalid block hash is an implicit “first seen” consensus rule.

jl2012

> On 18 Nov 2016, at 01:49, Eric Voskuil <eric@voskuil.org> wrote:
> 
> Actually both possibilities were specifically covered in my description. Sorry if it wasn't clear.
> 
> If you create a new valid block out of an old one it's has potential to cause a reorg. The blocks that previously built on the original are still able to do so but presumably cannot build forever on the *new* block as it has a different tx. But other new blocks can. There is no chain split due to a different interpretation of valid, there are simply two valid competing chains.
> 
> Note that this scenario requires not only block and tx validity with a tx hash collision, but also that the tx be valid within the block. Pretty far to reach to not even get a chain split, but it could produce a deep reorg with a very low chance of success. As I keep telling people, deep reorgs can happen, they are just unlikely, as is this scenario.
> 
> If you create a new invalid block it is discarded by everyone. That does not invalidate the hash of that block. Permanent blocking as you describe it would be a p2p protocol design choice, having nothing to do with consensus. Libbitcoin for example does not ban invalidated hashes at all. It just discards the block and drops the peer.
> 
> e