I just made a transaction at 30 sats/vB which sat 3MB from the tip. On the other hand, I double-spent that with a 60 sats/vB fee and that was at 1.1MB away from the tip.
Lets face it, the top 1MB of transactions will likely be included in the next block, so even if the mempool is congested as in your transaction is at 45MB from the tip or somewhere around that, you can kinda guesstimate how long it'll take to confirm by multiplying it by the average block time (10) and then waiting for 45*10 minutes. This is assuming you didn't use a ridiculously small fee like 10 sats/vB where the possibility of a rush of transactions bumping you a few megabytes down the tip becomes likely.
That being said, #1 is slightly more dangerous than #2 since because of the high-enough fee, the transaction won't stay in the mempool long enough to get dropped, and the only real danger I see in #1 (assuming you're not dealing with some random dude as LoyceV mentioned!) is a lazy scammer who double-spends on you 10 minutes after he broadcasts the transaction. Otherwise you can just tell him "wait X minutes (where X is MB from tip * 10 + some extra amount*) and it should confirm by then".
* Where the extra is something people can agree with like Celsius to Fahrenheit formula C x 9/5+ 32 = F minutes.
Topic: Which scenario is safer than the other? - page 2. (Read 296 times)
The first scenario is more safe.
Note that once a transaction receives the first confirmation, it no longer matters if it was RBF-enabled or not.
Whether it was RBF-enabled or not, the scammer needs to implement 51% attack.
Even if a transaction hasn't been flagged as RBF, it's possible that a miner includes another transaction spending same inputs with much higher fee.
It's also possible that the transaction has an uncomfirmed RBF-enabled parent. Once the parent is replaced by another transaction, all children will become invalid.
So, if you are going to accept an unconfirmed transaction for any reason (even if it is paying very high fee and hasn't been flagged as RBF), you should check if it has an unconfirmed parent or not.
If there's an unconfirmed RBF-enabled parent, it's very likely that it's a scam.
1. The transaction he sent you is RBF-enabled. He supposedly has an unfortunate emergency and leaves as soon as you receive the first confirmation on the blockchain
In this case, the person can scam you only if he can implement 51% attack or in the unlikely event we have a block reorganization (i.e another block has been mined simultaneously) Note that once a transaction receives the first confirmation, it no longer matters if it was RBF-enabled or not.
Whether it was RBF-enabled or not, the scammer needs to implement 51% attack.
2. The transaction he sent you is non-RBF. He supposedly has an unfortunate emergency and leaves although the transaction has 0 confirmations on the blockchain
It's more risky to accept this transaction. Even if a transaction hasn't been flagged as RBF, it's possible that a miner includes another transaction spending same inputs with much higher fee.
It's also possible that the transaction has an uncomfirmed RBF-enabled parent. Once the parent is replaced by another transaction, all children will become invalid.
So, if you are going to accept an unconfirmed transaction for any reason (even if it is paying very high fee and hasn't been flagged as RBF), you should check if it has an unconfirmed parent or not.
If there's an unconfirmed RBF-enabled parent, it's very likely that it's a scam.
There is always the "last resort" a very high fee CPFP transaction so it *will* be in the next block.
Who pays the fee would have to be discussed or you just eat the fee knowing that it's part of doing business and you got the funds.
If it's non rbf then you are 100% safe, without some massive double spend attack then it's not going to be in your wallet sooner or later.
But #1 by itself is more likely a scam.
Ignore everything I posted before. I misread the OP and did not see that there already was a conformation.
Once it's confirmed, unless they have some massive mining operations behind them to do a 51% attack, more or less you are safe.
If it's non RBF yeah, they might be able to spend some other inputs and invalidate the TX.
Was on mobile. My bad, keeping the original text for reference in case someone cares.
-Dave
You've met some random dude to purchase BTC from him. The dude sends you a transaction with a theoretically high-enough mining fee rate, but even after 2 hours of waiting it still isn't confirmed. He's desperately waiting for the tx to be confirmed so that you can give him the cash.. but the network happens to be congested, so now things become uncertain.
Here are two scenarios:
1. The transaction he sent you is RBF-enabled. He supposedly has an unfortunate emergency and leaves as soon as you receive the first confirmation on the blockchain
2. The transaction he sent you is non-RBF. He supposedly has an unfortunate emergency and leaves although the transaction has 0 confirmations on the blockchain
You are quite new to the crypto space so you give him the money anyway thinking it's enough.
Which of the two scenarios are now more likely to turn into a scam?
Here are two scenarios:
1. The transaction he sent you is RBF-enabled. He supposedly has an unfortunate emergency and leaves as soon as you receive the first confirmation on the blockchain
2. The transaction he sent you is non-RBF. He supposedly has an unfortunate emergency and leaves although the transaction has 0 confirmations on the blockchain
You are quite new to the crypto space so you give him the money anyway thinking it's enough.
Which of the two scenarios are now more likely to turn into a scam?
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