I never knew before that the first transaction could still be transferred or canceled just because the sender made a second transaction with a higher fee.
Imagine, you made a tx with lower fee. In recent times, lower fee tx requires more time to get confirmed. One of my tx with 2 sats per byte isn't confirmed yet. Nevertheless, since you used lower fee in the tx, the tx won't get confirmed. With the tx id, you were able to attract the mind of the seller (receiver) that you sent the tx. But since the tx isn't confirmed yet, if you create another tx with higher fee, miners will include the higher fee one in blocks. Therefore, the previous tx will no longer valid as that input has already been spent. 
Topic: Don't accept 0 confirmation tx - page 3. (Read 662 times)
Yes, I have read it and understand what the OP went through. To be honest I had never heard of a scam like this before and it was new to me. BTW you are a little faster than me to start thread, but good because the community will gain knowledge and warning.
I never knew before that the first transaction could still be transferred or canceled just because the sender made a second transaction with a higher fee. But that person's case has made me realize that unconfirmed transaction are anything but secure.
I never knew before that the first transaction could still be transferred or canceled just because the sender made a second transaction with a higher fee. But that person's case has made me realize that unconfirmed transaction are anything but secure.
This is a great tip and something that should apply to every cryptocurrency!
Bare in mind that some cryptos have a much, much faster blocktime and that period could be even longer.
Bare in mind that some cryptos have a much, much faster blocktime and that period could be even longer.
This reminds those Bitcoin enthusiasts to know how Bitcoin works properly before accepting Bitcoin as a payment. Yes, Bitcoin is irreversible once it is confirmed but it could be tricked by the double-spending method of scamming people if there's no at least 1 confirmation. I even not feel safe with one confirmation confirmed. For the sake of safety and security per Bitcoin transaction, at least 3-5 confirmation confirmed before accepting as a valid amount transfer to your wallet or even much better just wait for the minimum 6 confirmations.
source:
The rejected transaction was pulled by the network and mark as rejected. And that is could be you of you will not wait for even 3-5 confirmations to be processed.
source:
The rejected transaction was pulled by the network and mark as rejected. And that is could be you of you will not wait for even 3-5 confirmations to be processed.
A lot of users of Bitcoin are unaware of what double spend is and wallets like electrum adds the unconfirmed transactions to their address as soon as it is sent, making it easier for them to be tricked that they have already received the funds in there wallet.
Therefore, don't accept zero confirmation tx. Wait for at least 1 confirmation.
The 1 confirmation rule is sufficient for smaller transactions; below ~$1,000. If however a transaction involves a significant amount ~ $100,00 to $1,000,000 6 confirmations would be advisable, for it to be considered irreversible, although in reality what it means is that, the transaction would be too expensive to invalidate and the scammer would be spending more than the amount involved to attempt such an attack on the network. 
This is called "double spend transaction". It is one of the way to scam people. We need to be more careful not to rush into dealing with strangers. I always wait for the asset to be added to my wallet during this type of transaction.
I feel comfortable with 3 confirmations. Although I am so erratic at the moment, that it will probably be a lot more by the time I can check.
It is very easy scam to be realized and I don't know why there are people who are scammed by this. I am sorry for the loss of that person but still don't understand why.
If a person actually uses an exchange, a casino, requirement on confirmations is a thing to know of. From 1 to 3 confirmations will be required. It is applied commonly to avoid double spend attacks.
I am sorry if a person is scammed by this for the first bitcoin transaction ever made. If it is not a first bitcoin transaction, I am sorry for the very careless acceptance.
With small fund, wait for 1 confirmation. With big fund, wait for up to 3 confirmations to make sure that transaction is irreversible. The most annoying issue is wait for first transaction. You don't know how long you will have to wait to see the first confirmation. Fortunately, after the first confirmation, it is comfortable to wait for next 20 minutes (longer or shorter a little) to get 2 more confirmations.
https://en.wikipedia.org/wiki/Double-spending
https://en.bitcoin.it/wiki/Irreversible_Transactions
https://academy.binance.com/en/articles/double-spending-explained
If a person actually uses an exchange, a casino, requirement on confirmations is a thing to know of. From 1 to 3 confirmations will be required. It is applied commonly to avoid double spend attacks.
I am sorry if a person is scammed by this for the first bitcoin transaction ever made. If it is not a first bitcoin transaction, I am sorry for the very careless acceptance.
With small fund, wait for 1 confirmation. With big fund, wait for up to 3 confirmations to make sure that transaction is irreversible. The most annoying issue is wait for first transaction. You don't know how long you will have to wait to see the first confirmation. Fortunately, after the first confirmation, it is comfortable to wait for next 20 minutes (longer or shorter a little) to get 2 more confirmations.
https://en.wikipedia.org/wiki/Double-spending
https://en.bitcoin.it/wiki/Irreversible_Transactions
https://academy.binance.com/en/articles/double-spending-explained
Quote
As we can see, a merchant that waits for block confirmations will vastly reduce the risks of becoming a victim of double-spends.
Check this thread- https://bitcointalksearch.org/topic/how-is-this-possible-a-recent-transaction-suddenly-becomes-invalid-5279758
OP has been scammed because they accepted tx without a single confirmation. It's possible to manipulate a tx in such cases where scammer will send you the fund and make sure they have received what they have paid for and later they will create another tx with higher fee with the same input. The later tx will get confirmed and yours one will be invalid.
Therefore, don't accept zero confirmation tx. Wait for at least 1 confirmation.
OP has been scammed because they accepted tx without a single confirmation. It's possible to manipulate a tx in such cases where scammer will send you the fund and make sure they have received what they have paid for and later they will create another tx with higher fee with the same input. The later tx will get confirmed and yours one will be invalid.
Therefore, don't accept zero confirmation tx. Wait for at least 1 confirmation.
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