Bitcoin Forum

Hello,
The question is in the title. I know I can't do it on electrum, maybe on a Command Line Interface? It looks like you need 6 confirmations to confirm transaction...
Thank you very much for those who know!!

No you can't. Even a confirmation is difficult. Every confirmation basically means that a block has to be rolled back, or another block has to be mined at that height. This requires either the network to be on two different forks, with one of the fork containing your transaction and eventually accepted (in the case of competing blocks at the same height) or if a miner helps you. 6 confirmation is the amount of confirmations required that makes it improbable for an attacker without 51% of the network hashrate to reverse your transaction. So no, unless you're able to get a miner with significant hashrate to help you and attack the network, it is not possible.

No, the second you clicked send it went in the Mempool,
once in the mempool, a miner can add it to a block, ie: your 1st confirmation

So once the miner add it to the 1st block, (The 1st Confirmation)
it is basically gone and you have no way to retrieve it aside from asking the person that received it, to send it back.

FYI:
People need to realize, that when you click send, there are no take backs or do overs.
Which is one of the major points of crypto, no one can confiscate your crypto, you have to send it to them,
which is also the reason, you should be very certain before you click send.

The transaction is final once it reaches 1 confirmation. Some exchanges wait for 6 confirmations because it is nearly impossible for an attacker to reorganize six blocks worth of transactions.

I think for alts such as Litecoin, it may be better to wait until three confirmations (still 6 may be too much). In the unlikely scenario of a 51% attack, I don't think that the attacker will be able to revert more than 1-2 blocks. Still theoretically there is a possibility, especially with cryptocurrencies having lower mining hash rate such as LTC. With BTC, I would say that there is virtually zero chance that the transaction may be reverted after 1 confirmation. And if sufficient transaction fee is paid, then I am OK even with 0 confirmations.

Hmm, No.

Zero confirmations means no miner has accepted it into a block,
so double-spends are not only possible but easy even with bitcoin.

Any user can double-spend on anyone dumb enough to accept zero-confirmations.

User sends bitcoin and you accept a zero confirm,
walks out of your store with the product and immediately sends out another transaction with a higher transaction fee.
This cancel out the 1st payment to you as the 2nd payment is accepted insuring the 1st never is, and you just lost out.

FYI:
To pull this off the user needs two copies of the same wallet,
but it is very easy to pull off especially with BTC super slow 10 minute blockspeed.
No one in their right mind should ever accept any crypto coin without at least 1 confirmation.

For a small value transaction if the buyer pays enough fee to be accepted within the next block then there it is not so unreasonable to accept payment with zero confirmations. Bitrefill and Fold App have this policy and I believe BitPay allows it for non-rbf transactions. The percent of transactions signalling rbf is less than 20% and the amount of people who know how to use it and want to intentionally scam a merchant is so low that it is an acceptable risk for them to accept 0-conf.

In the scenario with any attacker holding 51% attack, the attacker can reorganize as many blocks as desired but that mostly depends on the profitability of doing so. The concept of 6 confirmation just means that the attacker needs to at least be able to outpace the network to be able to reorganize more than 6 blocks.

You need lesser hashrate for lesser confirmations as you're looking to reorg lesser blocks and thus having a better success rate. In the unlikely event of competing blocks, then it is completely possible for a transaction to be double spent, depending on the fork that forms the longest chain. 0conf transactions is less than feasible now... Trying to accept them will put you at a significant risk.

Depends on your risk analysis, fee market tends to fluctuate quite wildly. You likely would be safer with non-RBF and a high fee but that comes at an expense of having your user pay more and potentially get their transaction stuck. Not an issue that I recommend people to be dealing with.

The transaction you broadcast from your wallet will be confirmed if it is included in one block that brings the first confirmation for yours. The first confirmation takes time and depend on the fee rate you use for yours and the network (or mempool) status.

After you get a first confirmation, later confirmations are easy and automatic. The next one block, your transaction will get its second confirmation and so forth.

You can only be able to roll back the network if you own more than 51% of network hashrate. It is not easy.

Estimated cost for 51% attack on LTC (https://www.crypto51.app/coins/LTC.html)

After a single confirmation it's over, you won't be able to stop the transaction from getting verified on the blockchain, the only way around this is if you can contact the receiver to send back your LTC for you and if you don't know the receiver you are out of luck