What Happens to transaction in a 'reorg' ? \ stacker news ~bitcoin

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Monero is suffering reorg attacks due to a miner controlling over half of the mining power. The article cites that 118 transactions were invalidated and rolled back 36 minutes of transaction .

I'm curious if anyone can verify how a reorg attack plays out for my own understanding on the transaction level. Does this mean if I sent someone a utxo, and the transaction was confirmed in a block but that block was reorg'd, then the utxo was never actually spent and is back spendable in my wallet ? And the receiver that thought they had a utxo is SOL ? That sound right ?

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55 sats \ 4 replies \ @0xbitcoiner 15h

Does this mean if I sent someone a utxo, and the transaction was confirmed in a block but that block was reorg'd, then the utxo was never actually spent and is back spendable in my wallet ? And the receiver that thought they had a utxo is SOL ?

yes. yes. That's why we should be waiting for at least 6 confirmations (blocks).

👀 https://learnmeabitcoin.com/technical/blockchain/chain-reorganization/

0 sats \ 3 replies \ @BeeRye OP 15h

I see, so there is a serious risk for people that receive the payment such as merchants.

55 sats \ 2 replies \ @0xbitcoiner 15h

not so serious, Bitcoin is super secure. But it can happen, if they use the timechain (L1). Merchants usually use the Lightning Network because it's got near instant settlement.

33 sats \ 1 reply \ @BeeRye OP 15h

yes, i am thinking about that now how lightning helps mitigate this risk.

55 sats \ 0 replies \ @0xbitcoiner 15h

For merchants, it's got to be fast. Nobody can wait an hour (6 blocks) for a payment to go through.

55 sats \ 2 replies \ @senf 14h

Yeah, that's right. I have no idea about Monero, but with Bitcoin the transactions can still end up in a block if the input UTXOs haven't been changed. If a person has paid and received their goods and sees that this has happened, they could RBF and send the sats back to themselves.

0 sats \ 1 reply \ @BeeRye OP 13h

i see, and so the reorg attacker would spend their coins, do the reorg attack, and then if successful, be able to spend them again. Thus, the reason for a reorg attack is to be able to spend your money more than once...so the attacker needs to be coordinating the reorg with their own spends. Any other benefits to an attacker ?

0 sats \ 0 replies \ @senf 13h

That's right.

Any other benefits to an attacker?

They would also come in as the miner with all the new blocks, so they'd have the block rewards associated with those blocks involved in the reorg. They would have been able to do that or something close to it with honest mining too, so I'm not sure that would count as a benefit.