作者：George Kaloudis, CoinDesk
編譯：Felix, PANews
要點：
加密貨幣和區塊鏈的所謂「殺手級應用」之一，是能夠在沒有中心化金融中介的情況下交易各種資產。別管這些資產中的大多數什麼都不做，或據稱什麼都不做。人們透過交易它們獲得了巨大的回報。就像2020年每個人都從SHIB中致富，然後在2023年再次交易WIF和PEPE。
當早期資本湧入這些代幣時，首先在代幣上線CEX之前，透過自動做市商（AMM）在DEX購買。 AMM是去中心化的應用程序，可以匹配加密代幣的買家和賣家，而無需通過受監管的交易所，也無需KYC（如護照照片、駕照照片或多張自拍照）。你要做的就是連接加密錢包，透過AMM輸入想購買哪種資產，點擊購買就可以了。
這些AMM的有趣之處在於（除了避免身份檢查的便利性和隱私性之外），雖然加密KOL將加密貨幣和區塊鏈宣傳為股票市場的“下一個迭代”，但在某種程度上，股市比AMM更即時。
舉個簡單的例子：A想以100美元的價格買股票XYZ，而B則想以99美元的價格賣出股票XYZ。因為如今的金融市場是相當的互聯互通，C不知何故知道這一點（有合法和非法的方式來查找和處理這些資訊），並以99美元的價格從B手中購買了XYZ股票，然後立即以100美元的價格賣給了A。每個人都很高興：A得到XYZ股票，B得到99美元，C透過交易套利得到1美元。
現在，那筆賺錢的交易已經完成，隨著交易的結束，套利者C吞噬了這筆交易，股票XYZ的市場效率低下（A的買入價和B的賣出價之間相差1美元）。這一切都是即時發生的，也就是說是線性的，C必須在適當的時間介入A和B之間才能執行這筆交易，而且必須按照這個順序進行（從A到C再到B）。
儘管形式略有不同，這種類型的套利也可以在AMM中看到。假設您很早就聽說了SHIB，並且想在CEX上市之前購買一些。由於它不在交易所，你調用了基於以太坊的AMM，然後點擊按鈕購買SHIB代幣。當你下訂單時，訂單會被丟進一大批待定的以太坊交易中。其中一些交易可能是人們用USDC在網路上購買東西，但其中許多交易是SHIB或WIF或PEPE等代幣的交易。
這些交易在完成和執行之前，每個人都可以看到，因為它們都在一個叫做內存池（mempool）裡。如果用於交易的AMM因為市場效率低下而錯誤定價了SHIB（就像範例的股票XYZ一樣），網路上的某人可以建立一個以太坊交易，在您使用另一個AMM之前購買SHIB，然後將其出售給您以獲取利潤。
進一步舉個例子，假設您購買的SHIB相當多。在這種情況下，每個人都可以看到買入量很大且能影響市場的交易正在等待，可以圍繞你的交易進行交易，以利用市場效率低下和你的訂單影響市場的行情。
像這樣的交易可以歸類為三明治交易。有些人選擇了「三明治攻擊」這個術語，因為AMM無法將買家與預期賣家進行匹配，並且可能導致原始買家在交易完成之前損失慘重（想像一下，如果你想購買10億枚SHIB代幣，而由於AMM效率低而無法進行三明治交易，你只拿到8億枚）。
三明治交易和其他類型的「低效率發現」更廣泛地稱為最大化（或礦工）可提取價值（簡稱MEV）。 MEV的意思是，驗證交易的人選擇以對自己而不是交易者最有利的方式對交易進行排序。由於區塊時間（驗證交易所需的時間）不是即時的（在以太坊中，交易每12秒左右驗證一次），因此有足夠的時間進行套利交易，尤其是交易機器人。
考慮到這一點，不難想像MEV已經擴展到AMM之外。對於前面的技術爭論，一個合理的結論是：想做的事情越複雜，就越有可能出現MEV。
The discussion surrounding MEV is extensive. Is it good or bad? Is it illegal?
It depends on who you ask.
On the positive side, MEV is a free market that calculates the real cost of things on the blockchain by eliminating inefficiencies that will be exploited until the inefficiency is close to zero. On the negative side, MEV can be exploited by uninformed laymen and new users and exploited by professionals and advanced users.
Only Ethereum has been mentioned so far, because despite MEV’s first-mover advantage, MEV has not historically existed in Bitcoin. Although it exists in theory, in practice it is not economically feasible (except in very special circumstances).
You may be thinking: "No MEV? If the AMM based on Ethereum has MEV, then the AMM based on Bitcoin must also have MEV, right?"
You are right, but there is no AMM based on Bitcoin yet. This is because Ethereum is more expressive than Bitcoin, which means you can "do more with it," like create tokens with Doge or other memes, trade on AMMs, and get rich.
And because Bitcoin is not very expressive, there is not a thriving market or AMM for new coins on Bitcoin. How could AMM-related MEV opportunities arise if there are no new non-Bitcoin assets on Bitcoin? Exchange Bitcoin for other Bitcoins?
Yes. This is where Bitcoin’s MEV comes into play.
MEV is far less robust on Bitcoin than on Ethereum, and when experts discuss this topic, it always comes with a caveat.
Colin Harper, director of research and content at Bitcoin mining company Luxor Technology, said: "This is more like a game you can play, rather than MEV."
Three years ago, Bitcoin went through an update called Taproot , making the network more expressive. Through the Ordinals protocol, it is unexpectedly possible to make Bitcoin equivalent to NFT. This is what was previously meant by "exchanging Bitcoin for other Bitcoins": "NFTs" can work on Bitcoin because the Ordinals protocol is able to see which satoshis (the smallest unit of Bitcoin, one in 100 million) Arbitrary data is engraved on it, which can be pictures, text or other things. These collectibles are called inscriptions, which are different from NFTs (individual tokens). If you buy an Inscription instead of buying a brand new token like on Ethereum, you are just buying some Bitcoins that are special only from the perspective of the Ordinals protocol.
This is actually using Bitcoin to buy Bitcoin (of course, use more to buy less). Just like buying SHIB with ETH or USDC with USDT, buying Bitcoin with Bitcoin is an activity that can be done first.
Colin Harper explains: “When you sell Inscription on Magic Eden or other similar marketplaces, you are using PSBT (Partially Signed Bitcoin Transaction). The seller signs their half and when the buyer buys, they The transaction is completed with their signature, and the buyer pays the transaction fee. Therefore, if the NFT trader sees the transaction in the mempool, they can replace the original buyer's payment and address by broadcasting their own transaction (stealing it). A higher-fee RBF (Replacement of Fees) transaction to ensure their transaction is confirmed before the original transaction."
Although this is not quite the same as the pure MEV discussed in the first section of this article, it still looks like it. Like MEV: There is a mismatch between expected buyers and sellers because a third party steps in and offers miners more compensation in exchange for inscriptions, while miners maximize their own value in the transaction by accepting third-party transactions.
Bitcoin still has miners, and in the mining business, there are a few things that happen all the time that look like MEV.
A common example is empty block mining. Bitcoin periodically mines an empty block. The block is of no use to anyone except the miner who mined it, since no other pending transactions are verified except for the coinbase (lowercase "c", not the company) transaction that rewards the miner with the block. There are technical reasons for this situation to occur. The appearance of empty blocks is actually accidental, but it is difficult to say whether this is MEV and whether it is beneficial to Bitcoin.
There is also the cartelization of miners (PANews note: A cartel is a monopoly group that can easily occur when a small number of resources are fully controlled by several companies). Many Bitcoin miners now use mining pools to balance their income by mining collectively and receiving a corresponding share. This can create a problem, especially as mining pools get larger. As Walt Smith of the venture capital firm Cyber Fund wrote in a lengthy article titled “Bitcoin’s MEV”:
“…pool mining creates systemic risk by enabling savvy multi-block MEV by increasing the odds of consecutive block wins. Mining pools and other mining cartels enforce this by abusing pool economics Common block templates, blacklisting small miners doing non-standard block construction. Continued excess fees combined with economies of scale will trigger consolidation, creating a pathological cycle."
Currently, some mining pools control quite a lot. A portion of the network's computing power, or even two or three mining pools, can join forces to control more than half of the computing power. If a mining pool cartel wins enough blocks in a row, it can exercise monopoly power to maximize profits.
Another real-world example of Bitcoin miner behavior could be MEV: out-of-band payments. Bitcoin miners are paid for accepting transactions that are considered non-standard (either off-chain or via separate and seemingly unrelated Bitcoin transfers). Again, this is not pure MEV, as the extracted value does not appear on the blockchain as a result of shrewd program decisions. Instead, value is extracted by miners being paid more than they otherwise would have been paid.
Some researchers worry that out-of-band payments are the first step on a slippery slope that could obscure incentives. But miners are seizing the opportunity. Listed mining giant Marathon has launched a service called Slipstream to accept non-standard transactions.
The concern is that this backroom operation could lead to the privatization of the mempool, which is troubling on any blockchain. As CoinDesk’s Sam Kessler writes: “Most pressingly, there are concerns that mempool privatization could entrench new intermediaries in key areas of the Ethereum transaction pipeline.”
If most transactions are submitted to private mempools for processing Confirmed, then a small number of people (i.e. a designated few) can influence Bitcoin transactions. This would centralize the power of the blockchain, which is obviously an unacceptable situation for anyone who values censorship resistance.
There are other MEV-like examples on Bitcoin, which inevitably exist in some form and which network participants need to be aware of.
Related reading: Overview of the current L2 status data: How big is the MEV scale?
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