Chances of successful double spend RBF

[M4hadeva]

TLDR: What would be the chances of performing a successful Replace By Fee (double spend) before the block gets confirmed?
Scenario: I own a computer shop in Yangon, and I am looking into accepting Bitcoin payments at my shop. I am fairly new to crypto and I recently read about the Replace by fee (RBF) feature. My concern is: what if a customer comes and buys a MacBook or any product, completes the purchase with Bitcoin, then leaves the store and re-broadcasts a transaction with slightly higher fee back to themselves within the next 10 minutes.
How likely are RBF successful? Is there any way I can prevent this?
Thank you!

[abhiseshakana]

TLDR: What would be the chances of performing a successful Replace By Fee (double spend) before the block gets confirmed?
Scenario: I own a computer shop in Yangon, and I am looking into accepting Bitcoin payments at my shop. I am fairly new to crypto and I recently read about the Replace by fee (RBF) feature. My concern is: what if a customer comes and buys a MacBook or any product, completes the purchase with Bitcoin, then leaves the store and re-broadcasts a transaction with slightly higher fee back to themselves within the next 10 minutes.
How likely are RBF successful? Is there any way I can prevent this?
Thank you!

If that transaction has not confirmed yet, you need at least 1 block confirmation to wait before you give your products to your customer. Because the confirmed transaction is not bip-125 replaceable, so s/he can't perform RBF in that transaction.

[Beerwizzard]

First of all if you own some shitty shot and know nothing about cryptocurrencies then you shouldn't integrate them into your business. Don't be retarded.
If you still going to do this then you can safely do it via BitPay. Otherwise, you would have to wait for a couple of confirmations. During this time your client should wait with you. Unfortunately, you won't get rid of it.

[mocacinno]

Well, somebody doublespending the unspent outputs used as an input for a transaction is ALWAYS a possibility, as long as the transaction has 0 confirmations (the odds get very low after 1 confirmation since it would require a fork of the chain after 1 confirmation). This isn't a new problem since rbf was introduced...
 
If you're selling something cheap, you might not care and accept 0 conf transactions anyways, just to increase the shopping experience of your honest customers... I mean, i consider falling victim to a double spend about the same as getting payed with fake money or being the victim of shoplifting. It's a crime, and most people won't try to doublespend. The few people that do can probably be prosecuted, so it might be fine as long as you're not selling expensive goods.

If you're selling something expensive, it might be a good idear to wait  untill the funding tx has at least 2-3 confirmations.

If you can't wait this long, there are alternatives:

• Use an altcoin that has less average time between 2 blocks (with bitcoin, the average time between 2 blocks is ~10 minutes and the blocks are sometimes full so transactions with little fees might not be included in the first couple of blocks... Litecoin has an average time between 2 blocks of ~2.5 minutes, and the odds of these blocks being full is much smaller... So accepting LTC will significantly reduce the time your customer has to wait before his payment is confirmed)
• Use the lightning network. Altough a new customer that doesn't have open channels will still need an on-chain tx to fund a new channel AND the LN is inherently less safe than an on-chain transaction (altough it's much safer than accepting 0 confirmation transactions as valid payment).
• Let your customers open an account and let them fund this account with crypto beforehand. When they purchase goods deduct the amount they have to pay from their account

[dothebeats]

This is unlikely to happen if you impose a 1-block confirmation rule before handing out the goods you are selling. On top of that, make sure that people will be paying the minimum amount of fee recommended for the tx to confirm within the next block to lower the confirmation time needed. This might be annoying in part of buyer so you must have other ideas in mind to keep them entertained while you both wait for confirmations.

[Haunebu]

Time is the biggest factor that needs to be considered here op. You need to make sure that your customers can wait patiently until 1 confirmation, but this will require some form of creativity on your part.

I don't think many people are aware of the complicated stuff like LN etc which is why it is best to stick to the 1-confirmation rule in this aspect.

[Yakamoto]

TLDR: What would be the chances of performing a successful Replace By Fee (double spend) before the block gets confirmed?
Scenario: I own a computer shop in Yangon, and I am looking into accepting Bitcoin payments at my shop. I am fairly new to crypto and I recently read about the Replace by fee (RBF) feature. My concern is: what if a customer comes and buys a MacBook or any product, completes the purchase with Bitcoin, then leaves the store and re-broadcasts a transaction with slightly higher fee back to themselves within the next 10 minutes.
How likely are RBF successful? Is there any way I can prevent this?
Thank you!

Assuming that you don't immediately exchange the product and you wait for the actual transaction to go through and be completely confirmed, you won't have to worry about replace-by-fee fraud. Considering that it only takes 10 minutes to confirm the transaction, I'm sure the customer could wait that long in a worst-case scenario. The only real way to prevent RBF scams is to wait for the original transaction to be confirmed, but the chances of it occurring are actually quite low. I wouldn't be significantly concerned about it.

[jojohamasa]

TLDR: What would be the chances of performing a successful Replace By Fee (double spend) before the block gets confirmed?
Scenario: I own a computer shop in Yangon, and I am looking into accepting Bitcoin payments at my shop. I am fairly new to crypto and I recently read about the Replace by fee (RBF) feature. My concern is: what if a customer comes and buys a MacBook or any product, completes the purchase with Bitcoin, then leaves the store and re-broadcasts a transaction with slightly higher fee back to themselves within the next 10 minutes.
How likely are RBF successful? Is there any way I can prevent this?
Thank you!

I think the choice of altcoin will be your best
because the average confirmations time is low
For example a LTC would be appropriate, 2.5 minutes is what you will need and thus provide faster service to your customer.

[Genemind]

It depends on the coin that you're using to transact.
Better wait for the one block confirmation before exchanging your products. During the transaction periods, while waiting for the confirmation, some wallets are waiting for updates in order to increase their fee. Some unconfirmed transactions come out with the given system but in some factors, the most number of honest bitcoin don't attempt to defraud their sellers.

[ralle14]

It depends on the coin that you're using to transact.

It's obvious that OP is planning to use Bitcoin since the thread is posted here and he didn't said anything about altcoin. If altcoins have RBF you'll rarely use it and they only have a small time to double spend because altcoins usually have a faster confirmation time than Bitcoin.

Assuming that you don't immediately exchange the product and you wait for the actual transaction to go through and be completely confirmed, you won't have to worry about replace-by-fee fraud. Considering that it only takes 10 minutes to confirm the transaction, I'm sure the customer could wait that long in a worst-case scenario. The only real way to prevent RBF scams is to wait for the original transaction to be confirmed, but the chances of it occurring are actually quite low. I wouldn't be significantly concerned about it.

It's not always 10 minutes though and that's probably the best case scenario if there's enough fee in the transaction.

[Bitinity]

The only way to avoid getting scammed of Double Spending buyer is by waiting for confirmation. The more confirmations will be better, but do not need to wait for too many confirmations. I guess 3 confirmations is enough, buyers wont need to wait too long while on other side you feel confident with the transactions. Some gambling sites also requires 3 confirmations of deposit before user can withdraw their money. So I think 3 confirmations is standard.

[pooya87]

since others are suggesting "altcoins" i feel i have to warn you that with altcoins things can be more dangerous in some cases. for starters when it comes to a bitcoin transaction when the transaction is included in a block (has 1 confirmation) the chances of double spending drops about 99% and 3 confirmation makes it nearly impossible. the same scenario with altcoins does not exist. 1 confirmation in most of them (specially those with faster blocks and high rate of orphans) only decreases the chances of double spending from 1% to 50% depending on the coin.

[pawanjain]

Any person would only do a double spend attack only if the transaction is yielding him a good profit. So in order for this to happen, the product the user is purchasing should be an expensive one.
In this case, you can simply implement a rule saying that transactions above a particular amount needs 1 or 2 confirmations.
Example: Products above $100 needs 1 block confirmation.
May be you can put up posters in your shop showing up this rule. The product amount and number of confirmation is just an example and you can change the numbers are per your need.

[mocacinno]

Any transaction made on the Blockchain platform requires the required amount of Block to obtained before the transaction is considered complete. You need to execute the transaction, and it reaches 1 Block before completing the buy-sell. You cannot RBF as soon as they reach 6 Block and to perform RBF, you need to change the whole Block book that has achieved.

I don't mean to sound like a jerk, but I have re-read this post at least 5 times and it still makes no sense...

Is it a google translate issue, or are you just making things up?

[Thirdspace]

TLDR: What would be the chances of performing a successful Replace By Fee (double spend) before the block gets confirmed?
~
How likely are RBF successful? Is there any way I can prevent this?

if the transaction has a very low fee at a time of mempool size is considerably big (= congested network)
then the chance to perform successful RBF is pretty good
prevention: by requiring confirmation on that bitcoin transaction before letting customer leaves your store with the product

My concern is: what if a customer comes and buys a MacBook or any product, completes the purchase with Bitcoin, then leaves the store and re-broadcasts a transaction with slightly higher fee back to themselves within the next 10 minutes.

when you say "completes the purchase with Bitcoin", the transaction should have at least 1 confirmation
if it hasn't received any confirmation yet, you shouldn't handover the product to your customer
think of it as if you are accepting payment with debit/credit card,
the payment is consider done when you get confirmation from card issuer thru EDC device
in bitcoin peer-to-peer payment system, you get confirmation from bitcoin nodes in the network

[Cuk0ng_bitc0in]

before you make that decision. does the majority of the public adopt BTC or not? your management is very good. but you also have to see public enthusiasm adopting BTC and crypto. whatever platform you will use for BTC transactions. if the public around you does not adopt BTC. or public interest in BTC is very low. then you will experience losses.

[Pumared]

TLDR: What would be the chances of performing a successful Replace By Fee (double spend) before the block gets confirmed?
Scenario: I own a computer shop in Yangon, and I am looking into accepting Bitcoin payments at my shop. I am fairly new to crypto and I recently read about the Replace by fee (RBF) feature. My concern is: what if a customer comes and buys a MacBook or any product, completes the purchase with Bitcoin, then leaves the store and re-broadcasts a transaction with slightly higher fee back to themselves within the next 10 minutes.
How likely are RBF successful? Is there any way I can prevent this?
Thank you!

Before confirmation of the block is possible in some crypts, but after confirmation of the block the transaction does not enter

[figmentofmyass]

TLDR: What would be the chances of performing a successful Replace By Fee (double spend) before the block gets confirmed?
Scenario: I own a computer shop in Yangon, and I am looking into accepting Bitcoin payments at my shop. I am fairly new to crypto and I recently read about the Replace by fee (RBF) feature. My concern is: what if a customer comes and buys a MacBook or any product, completes the purchase with Bitcoin, then leaves the store and re-broadcasts a transaction with slightly higher fee back to themselves within the next 10 minutes.
How likely are RBF successful? Is there any way I can prevent this?
Thank you!

don't accept transactions as paid until they are confirmed on the blockchain---full stop. once a bitcoin transaction has one confirmation, it's extremely unlikely to be reversed.

some people will tell you to accept zero-confirmation transactions as long as they don't flag RBF, but they're wrong. a transaction is worthless until it's confirmed on the blockchain. it is very trivial to "double spend" an unconfirmed transaction whether or not it flags RBF.

[r1s2g3]

Any transaction made on the Blockchain platform requires the required amount of Block to obtained before the transaction is considered complete. You need to execute the transaction, and it reaches 1 Block before completing the buy-sell. You cannot RBF as soon as they reach 6 Block and to perform RBF, you need to change the whole Block book that has achieved.

I don't mean to sound like a jerk, but I have re-read this post at least 5 times and it still makes no sense...

Is it a google translate issue, or are you just making things up?

Same here. That user has no idea about RBF and even did not bothered to understand the RBF and posted the knowledge about 51% attack in RBF assuming both are same.

[sandra_x]

A double-spent is nearly impossible with the current level of POW on the bitcoin network, also to do a replace transaction by fee,one of the conditions is that the recipient's destination and other similar parameters have not changed.Overriding the first transaction with a second bit similar transaction with a bigger reward or fees to miners.