Topic: Don't accept 0 confirmation tx (Read 669 times)

But someone is ignorant about the crypto payments they should get the knowledge first before receiving the funds, maybe he lost the money but it is a good lesson and will keep him aware of this forever and also he might teach other people about which mistakes should be avoided to save ourselves from scams.

This also happened to me in the past. I agreed to sell an altcoin to a stranger in telegram. I was agreed because The guy wanted to pay BTC to me fast. And I will pay him later. That time I follow him as clever because without any reason no stranger can agree to pay fast without debating a ward. He sent me Bitcoin to my address and ask for the altcoin from me. I said to him to wait for at least one confirmation. But the guy blaming again and again that this is not like a business, he have to sell the altcoin, the market going down bla bla bla, I was strong since I have already got the bitcoin to my wallet , and saying him I can not send it before any confirmation. one, two, six hours even 1 days gone but the tnx is pending. after 1 more day maybe the tnx gone from tnx history.

It can give so much time to make a transaction again to cancel the previous transaction because the btc nodes confirm the latest transaction usually in 10 minutes and that will give ample time for the scammer to make a new transactions and to cancel the previous one.

As what had been mention by other users that the first transaction being made was being rejected. And remove from the network. Scammers really are brilliant in taking advantage of this kind of processmof bitcoin transaction. So we must all be careful instead not getting trick or outsmart by the scammers.

it is a tough call that someone will accept BTC without even knowing how the network is functioning, but you should never blame the victim

someone tried to allow BTC payments, and after scam like this one, he will probably give up on BTC payment, which is not a good thing for a mass adoption, and one should always show empathy to the victim, and not blame one to have not being too serious to read all the small letters included

Based on that story OP is a seller and he accepts Cryptocurrency for payment to his product, he is a newbie seller and naive, he should know how transaction works, he should have wait for the right number of confirmation before he send the product, every coin has a required number of transactions and he should be aware of that.

again you can't just give raw numbers based on a single factor while there are multiple important ones to consider. these numbers you posted here are for the case when the user is running a full verification node and the network is healthy (there is no forks planed, etc.) read my comment in first page for details: https://bitcointalksearch.org/topic/m.55311829

Technically, it is. Occasionally the network experiences what is called a stale block. This is when two blocks are mined in very close succession. The first block isn't finished being broadcast round the network when the second block is also broadcast round the network. Some nodes accept the first block, and some accept the second. The conflict is only resolved when the next block is mined, and whichever block it was built on top of becomes the accepted block, with the other one being rejected and becoming a state block.

Now, usually any transactions which were included in stale block would also be included in either its replacement or the next block, and so wouldn't be reversed, but it is possible for a transaction not to be included and therefore go from 1 confirmation back to 0.

Although the transaction is reversed (going from 1 confirmation back to 0), it is not cancelled. The transaction will still exist in the mempool to be picked up by some future block, unless someone successfully double spends or replaces it.

Hmm, since it's also a forum, you can't always trust a post from a random user.

Or maybe it's for a gambling/exchange that accepts 0-confirmation deposits that has some safeguarding against double-spend attempts like
not accepting RBF txns, should have optimal fee and no withdrawals until the deposit is confirmed.

Care to link the thread where it was posted?

As a newbie I am very happy to have lessons like this because these are going to help in future as reading here many scams and cheats happening with different peoples here in crypto world but this surely going to help many newbies because minimum 1 to 3 confirmations are ok for any payment but never go with 1 confirmation as this can give you shock and you can lost your hard earned funds thanks @RapTarX.

Technically, it is not possible to reverse a transaction which has been confirmed and included into the valid chain asides with an attack on the network.

Putting it into perspective; an attack on the network means an entity controls majority of the hashrate or more than anyone else, creating a monopoly on the network. This is very expensive and can not be realistically maintained for a long period of time.
51% is used to indicate one who controls majority of the network, this is the range where it becomes possible to manipulate the network and reverse already confirmed transactions, it is still very difficult to actually implement from here on. One who controls less percentages than that (<51%) can still try to manipulate the network but it is much less probable and still expensive, this is why there is an advisable range for transactions to be considered irreversible;

• 1 confirmation would be okay for low transactions as it would not be worth it for someone to try and reverse.
• For extremely large transactions, like $1 million and above, it is possible and profitable for someone who controls majority of the hashrate for a little while to manipulate the network and invalidate, so it is advisable to wait at least 6 confirmations.
• For intermediate amounts, between both extremes, 3 confirmations and above should suffice.

The deeper a block is in the chain the more secure it is, reason why it is advised to wait for more conformations when dealing with much larger amounts.

Is it possible to cancel a transaction which got one confirmation? Its not really possible from what I need because once the transactions included in the blocks then there is no way of reversing it other than 51% attack so we can trust 1 confirmation is enough for any transaction to get accepted or correct me if I am wrong here.

Yeah I have found several threads from stackexchange saying that 6 confirmations is the rule of thumb when it comes to how many confirmations needed in order for us to say that the transaction is secure and somehow irreversible. But what I can't manage to see again is their price to confirmation model they have done in that forum. It sorta goes like this.

0-1 Confirmations - up to 10$
3 Confirmations - 100$
6 Confirmations - 10,000$

The numbers above are made up but these is how they made the model explaining why these prices of transactions are safe depending on the number of confirmations.

There are multiple attacks which do double-spend a transaction with 1 confirmation.
Most of them either require a collusion with a miner or to sacrifice a block reward.

While it is technically possible, it is highly unlikely, not guaranteed to work out and too costly to perform.




Always at least 1 confirmation.
If the amount is extremely high (in your opinion), wait for 3-6 confirmations.

By connecting 6confirmations and double-spend, I'd say that it isn't what you've heard years ago.
But double-spending is an old term and it's even in the Whitepaper.

Double-spending can only be done with unconfirmed transactions.

Those additional required confirmations are for assurance that your confirmed transaction will be harder to manipulate by a miner who will do a "51% attack".
The deeper the block where the transaction is in the blockhchain, the harder it is to tamper with the transactions in it.
So it's recommended to wait for 6 confirmations for high-value transactions and 3-5 for medium risk, but you actually only need 1 to consider it as "paid".

How long has this been going on for?


So this is exactly the double spend scam i heard about from years ago?


So say someone send you btc and you send them money.  You need to make sure it has at least how many confirmations before you send them the money or give them cash?  Someone said if its less than a thousand dolllars, you can do x confirmations, if its smaller than a hundred dollars, x confirmations... but if its huge amount... always 6 confirmations?  So if someone send you 5000 dollars worth of btc, how many confirmations you need before you give them cash or online payment?

That basically is a RBF. That's how one would implement a RBF with core and the appropriate flag being set.



Actually, they don't.
That's the whole point of bitcoin. If it would require trust, it would have failed on what it was meant to achieve. A trustless, decentralized and uncensorable payment network/protocol.

Wrong usage can - under given circumstances - require trust.

It is entirely variable, and depends on the person receiving, their risk model, and how much bitcoin is being transferred. If I'm receiving money from a friend or relative I trust, then I'm going to be happy with zero confirmations for relatively large amounts. Conversely, if I'm receiving money from a complete stranger, then I'm going to wait for a couple of confirmations for even small amounts. A large business may accept zero confirmations for transactions less than 5 dollars, because the small amount of fraud they would experience is more than offset by the speed of being able to serve more customers. Conversely, someone for whom 5 dollars represents an entire day's wage is going to wait for several confirmations.

6 confirmations was picked as a completely arbitrary number.

Irrelevant when we are talking about Bitcoin, not Ethereum.

Good advice,
0 confirmation transaction can easily be canceled using only metamask.
A good example of this fraud is sending funds with 1 gwei gas fee. The tx is visible, but will be pending until ragnarok.

I already seen this kind of scam in social media platform they are looking for trade from other crypto currency  they are telling that they  will send first by using that tricks . Other will believe because there are incoming unconfirmed transaction that they can see in thier wallet  and that bogus traders will say many things and accuse you of being a scammer .he will tell you that you are a fake seller if you don't send the one he want to trade after having fake transaction .

I heard about this kind of situation where people fell victims to these strategies. I won't really consider the deal that has been done before I see some confirmation in the transactions because the unconfirmed transaction can also be unsuccessful at some point. One confirmation is enough though cause you can really sure that the funds will be going to your wallet after a few minutes.