He is most certainly confused and has a flawed understanding of Bitcoin. I can't seem to recall something in my thought process so I thought I'd ask. We know that blocks bigger than 1 MB from chain B would surely get orphaned on chain A. However, what about blocks from chain A being relayed to chain B (considering this would be a 'unilateral split')? I don't see why 1 MB blocks from chain A would get orphaned on chain B under current conditions. Care to elaborate?
This is where an unilateral split gets tricky, and why BU needs majority hash rate.
Let us say that block A1 is the last common block ( A's are less than 1MB). BU pulls the trigger at that moment. What does that mean ? They mine at least ONE B block, bigger than 1 MB: B1.
We now have: for BU nodes: A1 - B1
However, for old nodes: only A1 (B1 is invalid).
BU has more hash rate. It now builds a B2.
For BU nodes: A1 - B1 - B2
for old nodes: A1 (both other blocks are invalid).
Now, a "minority miner" mines A2, built on top of A1 (B1 and B2 are invalid blocks for him).
this is where your 2-dimensional thinking falls apart.
at this point . without A banning communication with the network
lets use blockheight numbers
For BU nodes: 460,001A1 - 460,002B1 - 460,003B2
for old nodes: 460,001A1 - 460,002A2
ALL nodes will still see 460003 and ask to get it to sync to highest height.
old nodes get the data. and reject it.
old nodes get the data. and reject it.
old nodes get the data. and reject it.
old nodes get the data. and reject it.
(endless orphan drama for minority and not syncing)
But of course not. For the old nodes, B1 and B2 are simply invalid blocks. So their height is at 460001. If I send an invalid block to another node, I suppose he's simply going to reject it, no ? Otherwise, I can bring down the whole bitcoin network by making 5000 successive bogus invalid blocks with erroneous hashes (not difficult) and tell the whole bitcoin network that we are 5000 blocks ahead ? Everything comes to a grinding halt with such a simple attack ?
Of course not. B1 and B2 are simply considered invalid blocks by old nodes. The old nodes will all agree that they are at height 460001. And those nodes receiving blocks B1 and B2 will reject them, and not even propagate them. But all BU nodes will accept them, propagate them, and their counter will be at 460003. An old node asking a BU node to send him the blocks, will conclude that this node is "confused". Otherwise, I can bring down the whole bitcoin network with one single "confused" node 5000 fake blocks in the future.
Period.