Trustnodes reported on December 19 that in the past month, there have been more than 3500 double spending attempts on the Bitcoin Cash (BCH) network.
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In the past 24 hours alone, such double spend transactions have exceeded 185.
However, in the vast majority of cases, the first broadcast transaction was successful, and 90% of legitimate transactions were confirmed, far exceeding those that attempted to steal funds through double spending.
However, in the past month, 337 double-spend transactions have been confirmed, usually with an amount of 0.15 BCH and a value of about $ 30.
A double spend transaction is, for example, sending the 0.15 BCH to the restaurant's payment address when you pay for dinner, and then you quickly try to send the 0.15 BCH to your own address or your friend's address.
In 90% of the cases, once the transaction is broadcast on the web, the restaurant will think you have paid. However, in 10% of the cases, the transaction will not be confirmed because the second transaction is already packaged by the miner.
In Bitcoin, the above functions are incorporated into the protocol level through "Replace by Fee" (RBF). This "legalization" double spends, because if the cost of the second transaction is higher, the miner will automatically package the second transaction.
We say this because miners are free to choose which transactions to pack, or sometimes they do not pack any transactions, but just mine empty blocks.
Therefore, just like in Bitcoin, if a miner is willing, they can choose a transaction with a lower fee, and in BCH, they can also choose a transaction with a higher fee, even if the transaction fee with a higher fee is not seen first.
Miners are not necessarily malicious. Many successful double spend transactions are sent within a second of the first transaction. Usually the first broadcast will still be broadcast faster, but good software will see the double spend attempt, so it will revert the transaction to the waiting confirmation state.
However, some merchants prefer to consider this 10% as a business cost, either because they do not realize the need to monitor the double spend attempt by listening to the node, or because they think that double spend causes The loss is not worth mentioning.
However, a supporter of Bitcoin Cash believes that the double spending of merchants shows that RBF works on Bitcoin as expected. A point-of-sale vendor said he might abandon both Bitcoin and Bitcoin Cash. Caleb Yeoh, founder of TravelbyBit, said:
"If we see more such transactions happen, we will have to stop trading on the Bitcoin and Bitcoin Cash chains of all merchants in Australia."
He also said that because the Lightning Network (LN) was designed to pay for dinner, they may only stick to Bitcoin Lightning Payment.
As you may all know, LN is locked Bitcoin, and the account is encrypted and saved through a fairly complicated network, which is composed of a set of different nodes and usually works normally, but it has quite a few problems.
There are problems, partly because it is still new, and partly because it tries to solve the double spend problem through game theory.
However, this might be a solution for paying dinner, especially in the Bitcoin network, otherwise you have to wait 10 minutes until the block is confirmed.
If you only pay for a dinner, you don't have to wait to use the BCH network, because based on the calculation of about 50,000 BCH transactions in the past 24 hours, the proportion of successful double spend is far below 1%.
Obviously, these 50,000 transactions are probably not all merchant payments, but for 1.5 million transactions per month, 300 double spends are just a small number.
However, we should keep in mind that double spend transactions may occur before a transaction is confirmed, or even in extreme cases.
This applies to both Bitcoin and BCH, and in extreme cases it also applies to the Lightning Network, but the number involved is small. For the amount you really care about, you must wait at least one confirmation, six are the best.