Is double spending easy to do? Burguer king accepting zero confirmation transact

[TryNinja]

However those 100 sat/byte tx will stop coming sooner or later, making room for 1 sat/byte tx. From my experience,  sooner than later.
I never saw a dropped Tx, I will take a look if I can find one.

I keep making 1 sat fee tx and they keep getting confirmed within a few hours. As I said, I made one last week during our price spikes. No issues ,8 hours to get 1 confirmation.

I think more people should do 1 sat/byte tx.
Most of those 100 sat/byte are probably done by exchanges and shitful wallets which don't let users control fees, artificially inflating fees to benefit miners... literally abusing newbies lack of knowledge.  But that's another discussion..

Yes... that’s the situation NOW. This in no way means 1 sat/byte transactions are drop-safe. What happens if suddenly someone starts spamming the mempool like they did some years ago? Or if China starts encouraging BTC usage and a big part of the population follows them? Possibilities.

You never saw a 1 sat/byte get dropped =/= no 1 sat/byte have ever been dropped. I have seen plenty and limiting facts to what you saw is wrong. Wasn’t you here when the mempool hit its ATH and you literally had 1-3 sat/byte stuck for days? You can’t deny that... it happened. It’s a fact.

I can literally spend million in 100+ sat/byte tx for weeks. Isn’t that possible and totally viable if I have the money to burn? How can you deny that and affirm 100 sat/byte tx will stop showing up? You don’t know that. And I personally had 1 sat/byte txs get stuck for days.

[bitmover]

You never saw a 1 sat/byte get dropped =/= no 1 sat/byte have ever been dropped. I have seen plenty and limiting facts to what you saw is wrong. Wasn’t you here when the mempool hit its ATH and you literally had 1-3 sat/byte stuck for days? You can’t deny that... it happened. It’s a fact.

You are the one denying it, saying that 1 sat byte get dropped and not stuck. I saw that, it was a fact: they didn't drop, they were waiting for confirmation for some hours/days, in the All Time High Congestion. Just like I said before.

Yes... that’s the situation NOW. This in no way means 1 sat/byte transactions are drop-safe. What happens if suddenly someone starts spamming the mempool like they did some years ago? Or if China starts encouraging BTC usage and a big part of the population follows them? Possibilities.

...

I can literally spend million in 100+ sat/byte tx for weeks. Isn’t that possible and totally viable if I have the money to burn? How can you deny that and affirm 100 sat/byte tx will stop showing up? You don’t know that. And I personally had 1 sat/byte txs get stuck for days.

TryNinja, I get your point. Ok, You want to justify that we shouldn't use 1 sat byte fees, but we should use higher fees. I don't agree, but that's ok.

Your "possibilities" like a suddently BTC adoption that will make BTC become highly used by common people in a few hours, or that someone very rich like Jeff Besos is going to spam the network with 100sat/byte for months didn't convince me.

Those "peaks" of congestion are much more like an attack (when BCH was listed in coinbase for example and BCH were spamming the network) or very uncommon situations, and they don't last for more than like 2 days.

I will continue using 1 sat /byte fees as I always did, since 2017, and I am ok with that. I know someday one transaction my be dropped, although it is very unlikely and I have never seen it, and I have done at least 30 1sat/fee txs. (and if it get dropped, I will sent it again with 1 sat byte fee until accepted!)

I never heard about such case (or i forget about such case), do you remember which payment processor did it?

I had to research a little.. It was BitPay.
I've found some links somehow related to that too, but not 100% what I was expecting:
https://www.reddit.com/r/btc/comments/4p4ruo/bitpay_no_longer_accepting_zero_confirmations/
https://www.reddit.com/r/btc/comments/91rau3/0confirmation_payments_are_they_safe/e307f0m/
https://www.reddit.com/r/Bitcoin/comments/22pnwu/if_0confirm_transaction_are_not_safe_why_does/

This is certainly a very interesting case. So there are payment processors using 0 confirmation transactions.

I think that for small values there is certainly very few people who are willing to scam using this RBF process.
And it is possible to calculate a fee to compensate scammers: If 1% of all people do a successful double spend (RBF whatever the name) than you just charge 1% on fees. Burguer king is doing that somehow, but using 4% fees according to the journalist.

https://es.cointelegraph.com/news/i-used-bitcoin-to-pay-for-a-burger-at-burger-king
“La comisión es poco más de 4% para todas las monedas sin excepción, no manejamos tasa BTC/VES si no crypto/USD, y cada comercio decide a su vez la tasa USD/VES, igualmente el fee de red lo decide el usuario”, puntualizó Jorge Faría, el CEO de Cryptobuyer.

Translation: "Commission fee is a little more than 4% for all currencies with no exception..."

[pooya87]

anyone who has ever accepted 0-confirmation transactions have been doing a lot of risk assessment on those transactions then accepted them. it is not like they accept just about anything. RBF is one of the things that will be checked. basically they first connect to a large number of bitcoin nodes and whenever a transaction is received they check to see if it is propagated among all of those nodes and whether they have any conflicting tx (one way of double spending is race attack). then the fee comparison and how much lower or higher the fee is compared to high priority transactions. and more importantly checking the parent transactions (the inputs). the tx at hand may be paying a high fee but the input may not even be confirmed or have a high fee.
with this simple assessment the receiver could decide how much risk that transaction has and come up with a number using a simple formula automatically and when that number is lower than a threshold the system automatically accepts the payment.
there is a block explorer that does this too: https://dev.blockcypher.com/#confidence-factor

[Pmalek]

I never heard about such case (or i forget about such case), do you remember which payment processor did it?

Payment processor who accept 0-conf usually require transaction with high fees, require non-RBF transaction or have upper limit of Bitcoin amount allowed for 0-conf.

The exchange Liquid does it as well. They credit their user's accounts for transactions with zero block confirmations. They claim that the deposits are credited within 10 seconds. If the mining fee is too low they require 1 confirmation. They are able to monitor the transactions as they propagate across the network and determine whether or not it will be confirmed successfully.

I guess it is not that uncommon.   
https://blog.liquid.com/fast-bitcoin-deposits-are-now-even-faster-on-liquid

[TryNinja]

You are the one denying it, saying that 1 sat byte get dropped and not stuck. I saw that, it was a fact: they didn't drop, they were waiting for confirmation for some hours/days, in the All Time High Congestion. Just like I said before.

I’m presenting a fact. These txs CAN be dropped if they get stuck for too long. This HAPPENED WITH ME. Nodes DO drop transactions. It is possible and this opens a window for users to “replace spam” the transaction and steal from Burker King’s processor. That’s the whole point of the discussion. People CAN steal BK and send the tx back to them.

TryNinja, I get your point. Ok, You want to justify that we shouldn't use 1 sat byte fees, but we should use higher fees. I don't agree, but that's ok.

Your "possibilities" like a suddently BTC adoption that will make BTC become highly used by common people in a few hours, or that someone very rich like Jeff Besos is going to spam the network with 100sat/byte for months didn't convince me.

Those "peaks" of congestion are much more like an attack (when BCH was listed in coinbase for example and BCH were spamming the network) or very uncommon situations, and they don't last for more than like 2 days.

Please quote me when I said you/we shouldn’t use 1 sat/byte transactions. I never did that.

The last major spam lasted days and even months w/ spam waves, not 2 days. This sounds like a very arbitrary number from you.

I will continue using 1 sat /byte fees as I always did, since 2017, and I am ok with that. I know someday one transaction my be dropped, although it is very unlikely and I have never seen it, and I have done at least 30 1sat/fee txs. (and if it get dropped, I will sent it again with 1 sat byte fee until accepted!)

Good. You should as long as the mempool is empty and allows you that. Now, when you see a big congestion, you will see your tx won’t get confirmed in 24 hours. And this is a really big problem for BTC that WILL happen in the current state OR won’t let BTC go mainstream. Don’t go denial on that

You can keep pushing them, making them never really get dropped (dropped? Put it back). The whole point of the discussion is users seeing the BK tx getting dropped and not pushing it back, but spending somewhere else and stealing that.

[NotATether]

It would only be worth replace scamming Burger King stores in that region if more people order from there on average (and only the BTC orders count) compared to other fast food chains.

Even then, it would also depend on how much of their revenue from orders are being stored in bitcoin in case the attackers specifically target Burger King's entire earnings and not just a few orders, and how much the orders cost. Attackers would not be willing to spend hundreds on hash power to mine as many blocks as there are confirmations just to steal the equivalent of $10 in BTC per order.

please correct this lazy usage of the expression "double spending"


double spending is not possible in the Bitcoin protocol, you are referring to something else (abusing people who accept zero confirmation tx A by outspending the fees on tx A with tx B that includes the same inputs as tx A, but with a higher fee).

This technique should have a more appropriate name, "replace scam" or somesuch. If double spending was possible in Bitcoin, the outcome of this technique would be that both the sender and the receiver would  get the BTC from the outputs in tx A, and tx B would also be confirmed providing it was seen by the miner before tx A is mined. Also, the 21m supply limit would of course be circumventible, and rampant inflation would ensue

again, Bitcoin cannot be double spent

Instead of calling this particular attack a double spend or a 51% attack it ought to be called a diverted transaction attack. Double spending is what it was called in the 2008 white paper so that's what confused everyone. Virtually no article or website on the internet is calling this anything else besides double spending and that is part of the problem. The term is deceptive by nature.