科學家居然還能這麼搶比特幣NFT？

Over the past week, more and more friends have been asking the editor a question—

Why didn't the NFT purchased on a "locked" Bitcoin NFT trading market like Magic Eden arrive in the end? Checking the purchase transaction, it shows that the transaction was replaced, and the item was "sniped" by someone else.

The answer is: you've been "RBF'd".

In fact, this is not a new issue. At the end of November last year, the "OrdiBot" series issued on Magic Eden Launchpad became the first well-known victim, and @mulan_art's "Unigraphs" series was also delayed in its release on Magic Eden Launchpad, precisely because at that time, "RBF" allowed any non-whitelisted user to bypass the whitelist mechanism and "front-run". Subsequently, Magic Eden made fixes to this issue on its Launchpad. Now, whitelisted users on Magic Eden Launchpad no longer need to worry about being "RBF'd". (Related reading: Whitelisted users Mint sniped by "highway robbers", Ordibots will re-airdrop to compensate for losses)

The solution is to mint the "Unigraphs" transaction

At the end of last year, someone used 0.0334 Bitcoin to "front-run" the transaction of 50 million BRC-20 Token $RATS.

And last month, "Quantum Cat" cat0673, who owns the "Golden Cloak" (entitling to a Taproot Wizards for free in the future), the first buyer to submit the transaction, was also "front-run" by another buyer who paid an additional $180 miner fee. The final buyer then resold it for 1.9 Bitcoin.

"Quantum Cat" cat0673

Recently, the booming Bitcoin ecosystem has caused more and more friends to encounter this issue, with more and more discussions. Early this morning, the editor has been wondering why the Bitcoin network's fees remain high. Despite yesterday evening to this morning being a day of project launches, the on-chain inscription situation does not seem to have caused congestion for BRC-20 or small image projects. Now the editor finally understands why—over 30% of the fees in many blocks are due to "RBF" sniping...

At this point, you may wonder: on platforms like Magic Eden, once an item is purchased, no one else should be able to click the buy button on the webpage. How are these "front-runs" achieved?

PSBT Transaction Mechanism Leads to RBF "Front-Running"

First, we need to understand that Bitcoin NFT trading markets like Magic Eden use PSBT, which stands for "Partially Signed Bitcoin Transactions". Simply put, both the buyer and seller sign based on the transaction information template provided by the NFT trading market. The seller's signature is completed when the item is listed, while the buyer completes theirs when making the purchase. The market then combines the two signatures and broadcasts them. (Related reading: Ordinals founder refutes Yuga Labs auction, why PSBT is the solution for Bitcoin NFT trading?)

However, the problem arises once the transaction enters the mempool. After the combined transaction is broadcast, the seller's part of the signature becomes visible to everyone because the transaction has entered the mempool. Once the seller's signature is exposed, it means that anyone can sign the transaction as a buyer.

As a result, the mempool effectively transforms from a "memory pool" to a "PVP pool"—due to the relatively long time interval between adjacent Bitcoin blocks, after the initial transaction is broadcast, if a "sniper" sees an opportunity for "front-running", they can re-sign a buyer transaction for themselves using the exposed seller signature, then use RBF to significantly increase their transaction fee rate, and miners will naturally prioritize packing the transaction with the higher fee. (In simple terms, RBF stands for "Replace by Fee", allowing for faster transaction confirmation by paying a higher transaction fee)

Of course, "snipers" also have their moments of failure. For example, the "RBF" sniping of NodeMonkes mentioned by @robertjfclarke in March this year failed because the F2Pool that mined the block did not allow "full RBF", resulting in the front-run transaction not being packed. The end result was that the initial buyer successfully acquired the NodeMonkes, which was about 60% below the floor price at the time, and made a profit of 0.2629 Bitcoin half an hour later.

Bitcoin's "MEV" Causing Fee Estimation Failure?

In fact, the RBF front-running caused by PSBT and the gas bidding on Ethereum are similar, with the main difference being that Bitcoin's block confirmation time is longer. In Ethereum, a new block is often produced in about 10 seconds, making it clear that it's a "race". The various concepts on Bitcoin may be slightly less familiar, but in reality, the effects of RBF front-running and MEV on Ethereum are somewhat similar.

If the Bitcoin ecosystem continues to be hot, for assets with good liquidity and market performance, more and more people will compete for arbitrage opportunities. The editor has already seen projects specifically providing sniping tools, such as @goldmine_tools. If such a situation really occurs, for assets that are highly sought after, the estimated block fees will actually experience a certain degree of failure, essentially turning transactions into a "auction" with fixed prices but requiring bidding for miner fees, making miners happy.

RBF History: escalating fees benefit miners

As for trading markets like Magic Eden, it may just need to better educate users on the actual process of purchasing NFTs and then optimize the NFT purchase process based on this. For example, providing an RBF tool, changing the current front-end page lock to "This NFT has a TX Pending", and allowing users to pay higher fees. This is how NFT aggregators on Ethereum work, displaying a Pending prompt but allowing users to increase Gas to front-run.

Conclusion

As we conclude, you may be wondering about a question that concerns many—If you've been RBF'd, will you lose the miner fee and the money spent on buying the item?

No, you won't.

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