By Bitcoin Tímarit - fyrir 3 mánuðum - Lestur: 11 mínútur
Miner Extractable Value (MEV) og forritanlegir peningar: The Good, The Bad, and The Ugly
Kjarni Bitcoin’s security model relies on this basic game theory—miners, armed with their digital pickaxes, are in a relentless chase for profit. And it’s this pursuit that keeps the network secure. Basic vanilla mining involves producing blocks to earn the block rewards and transaction fees, but have you ever considered that miners might have other ways to extract value from the blockchain beyond this standard mining process? Are there other avenues for profit on the blockchain where miners can leverage their unique position as validators?
Hvað er MEV?
Í vinnusönnunarkerfum, "Miner útdraganlegt gildi"(MeV) er hugtak sem lýsir hagnaðinum sem námumenn geta aflað sér með því að hagræða því hvernig viðskiptum er forgangsraðað, útilokað, endurraðað eða breytt í blokkunum sem þeir vinna. Hins vegar, eftir uppfærslu Ethereum í Ethereum 2.0, sem færði netið yfir í sönnun á hlut, hefur hugmyndin um MEV tekið á sig nýtt nafn og er nú vísað til sem „hámarks útdraganlegt gildi“ í sönnunargögnum. Í þessu samhengi eru það blokkartillögurnar í stað námuverkamanna - sem eru sannprófunaraðilarnir - sem hafa tækifæri til að draga þetta gildi.
Miners (eða löggildingaraðilar í Ethereum) hafa sérstakt hlutverk í þessum netum sem staðfesta viðskipti í blokkum. Staða þeirra setur þá skrefi á undan öðrum notendum og gerir þeim kleift að ákvarða endanleg röð viðskipta í keðjunni. Inni í blokk eru færslur venjulega pantaðar með hæstu gjöldunum efst, en af og til opnast tækifæri sem gera námumönnum kleift að taka auka hagnað með því að breyta röð viðskipta markvisst í eigin þágu.
Þú gætir hugsað, hver er skaðinn við að láta námuverkamenn taka smá aukahagnað af toppnum? Áhyggjurnar byrja aðeins að koma upp þegar sumir þessara námuverkamanna, þeir sem eru búnir háþróaðri greiningargetu og öflugri tölvuvinnslu, geta greint og nýtt MEV hagnaðartækifæri á skilvirkari hátt en aðrir.
These opportunities might not always be easy to spot, but the more value that can be extracted through analyzing the chain, the stronger the incentive becomes for research teams equipped with bots to do this work. Over time, this disparity in miner's profit-making ability creates a trend toward centralization within the network. Ultimately undermining the core principle of the blockchain: decentralization.
This is exactly the scenario the Bitcoin developer community is aiming to prevent when considering how best to manage more expressivity on Bitcoin.
Af hverju viljum við forritanlega peninga?
Sögulega, Bitcoin has operated with relatively simple smart contracts. However, this model struggles with even moderately complex transactions. Bitcoin Script can only validate authentication data, it doesn’t have the capability to impose speed limits on transactions or define coin destinations because Bitcoin Script doesn’t have access to transaction data.
As a somewhat separate issue, working with and writing Bitcoin smart contracts can be challenging for users who don't fully grasp its security requirements. A proposed feature, known as ‘vaults,’ aims to solve some of these pain points by introducing time-locked conditions for transactions. Essentially, vaults could serve as an emergency “escape hatch,” allowing users to recover their funds in the event of compromised private keys. But features like this are only possible with more expressivity.
Ethereum is widely recognized for its highly expressive scripting capabilities, but it also notably struggles with the issue of MEV. Most users generally assume that Bitcoin has no MEV, in stark contrast to Ethereum, which is viewed as a wild frontier for it. But is this the full story?
Hvetja meira svipmikill snjallsamningar sjálfkrafa til fleiri MEV-sviðsmynda?
Það eru nokkrir þættir sem stuðla að MEV: (1) gagnsæi mempool, (2) gagnsæi snjallsamninga og (3) tjáningarhæfni snjallsamninga. Hver þessara þátta opnar nýjar rásir fyrir MEV, við munum fara yfir hvern og einn hér.
Hið slæma: (1) Mempool gagnsæi
eins Bitcoin's mempool, the mempools of most blockchains are fully transparent, open, and visible, so that everyone can see what transactions are pending before being validated and confirmed in a block. Bitcoin blocks typically take about 10 minutes to find, which theoretically gives miners that same amount of time to take advantage and front-run.
In practice, on Bitcoin, this isn’t a source of MEV for a few reasons: (1) Bitcoin transactions are simple enough that no miners have a significant analytic advantage over other miners, and (2) Bitcoin transactions generally don’t execute multi-asset transactions such as swaps or open trades that could be front-run.
Berðu þetta saman við Ethereum, sem er með flóknustu fjöleignaviðskipti sem eiga sér stað á opinberum dreifðum kauphöllum (DEX). Opinberlega er blokkunartíminn á Ethereum 15 sekúndur, en á tímabilum með mikilli mempool-umferð geta nauðsynleg gasgjöld fyrir tafarlausa blokkun auðveldlega farið yfir hundrað dollara. Fyrir vikið bíða færslur með lægri gjöldum mínútur eða jafnvel klukkustundir áður en þær eru teknar með í blokk. Þetta getur lengt gluggann fyrir þessi svívirðilegu tækifæri til að koma fram, sem eru nú þegar algengari á Ethereum vegna mikils verðmætis sem er pakkað inn í lag-2 tákn.
The slæmur: (2) Snjall samningur gagnsæi
In Bitcoin “smart contracts” are the simple locking and unlocking mechanism inherent in Bitcoin Script. The transaction values, sender, and receiver details are all publicly visible on the blockchain. While this complete and naked transparency isn’t ideal from a privacy perspective, it’s part of how Bitcoin allows all participants in the network to verify the full state of the blockchain. Any observer can analyze these contract details, potentially opening the door to certain MEV-related strategies.
En Bitcoin scripting language is, by design, quite limited, focusing primarily on the basic functions of sending and receiving funds, and validating transactions with signatures or hashlocks. This simplicity inherently limits the scope for MEV strategies on Bitcoin, making such opportunities relatively scarce compared to other chains.
Platforms like Ethereum, Solana, and Cardano also have fully transparent smart contracts, but they diverge from Bitcoin by also having highly complex and expressive scripting languages. Their Turing-complete systems make it possible to theoretically execute virtually any computational task which has come to include: self-executing contracts, integration of real-world data through oracles, decentralized applications (dApps), layer-2 tokens, swaps within DEXs, and automated market makers (AMMs). These come together to foster a rich environment for MEV opportunities. Zero-knowledge-proof-based schemes, such as STARKex, could theoretically avoid some of these issues, but this trade-off would come with other complexities.
Hinn ljóti: (3) Snjall samnings tjáning
The MEV opportunities are so lucrative on some chains that there are “MEV trading firms” bringing in “high five figures, mid six figures” in profits a month. This trend has become so prominent that there are public dashboards dedicated to scanning for profitable opportunities on Ethereum and Solana. Their profitability is generated by executing the full basket of MEV strategies: front-running, sandwich trading, token arbitrage, back-running, and liquidations to name a few. Each exploiting a different smart contract dynamics for profit.
Sumar af þessum MEV aðferðum eiga við bæði lag-1 og lag-2.
Generalized Front-Running: Bots scan the mempool for profitable transactions, and then front-run the original transaction for a profit.Sandwich Trading: The attacker places orders both before and after a large transaction to manipulate asset prices for profit. This strategy leverages the predictable price movement caused by the large transaction.Þá eru ákveðnar aðferðir einstakar fyrir lag-2 tákn og snjalla samninga.
Arbitrage Across Different DEXs: Bots exploit price differences for the same asset on various DEXs by buying low on one and selling high on another.Back-running in DeFi Bonding Curves: MEV bots capitalize on predictable price rises in DeFi bonding curves by placing transactions immediately after large ones, buying during uptrends, and selling for profit. DeFi Liquidations: MEV bots spot opportunities in DeFi lending where collateral values fall below set thresholds, allowing validator's to prioritize their transactions for buying the liquidated collateral at lower prices.Flækjustig samninga stuðlar verulega að áskorunum sem tengjast MEV.
Re-entrancy Attacks: These attacks exploit smart contract logic flaws, allowing attackers to repeatedly call a function before the first execution completes, extracting funds multiple times. In the context of MEV, skilled individuals can significantly profit from this, particularly in contracts with substantial funds.Interconnected Contracts and Global State: On platforms like Ethereum, smart contracts can interact, leading to chain reactions across several contracts from a single transaction. This interconnectivity enables complex MEV strategies, where a transaction in one contract may impact another, offering a chain reaction of profit opportunities.Hluti af vandamálinu hér er að heildarverðmæti sem skapast af táknum og dApps byggðum á lag-2 fer oft yfir verðmæti innfæddrar eignar blockchain á lag-1, sem grefur undan hvatningu löggildingaraðila til að velja og staðfesta viðskipti eingöngu byggð á gjöldum.
Til að gera illt verra eru mörg af þessum tækifærum ekki bundin við netprófunaraðila. Aðrir netþátttakendur með MEV skönnun vélmenni geta keppt um þessi sömu tækifæri, sem veldur netþrengslum, hækkar gasgjöld og hækkar viðskiptakostnað. Þessi atburðarás skapar neikvæð ytri áhrif fyrir netið og notendur þess, sem allir verða fyrir áhrifum af verði hærri viðskiptagjalda, þar sem keðjan verður óhagkvæmari og dýrari í rekstri. MEV í DeFi er svo algengt að notendur hafa næstum samþykkt það sem ósýnilegan skatt á alla í netinu.
Koma þessi MEV tækifæri náttúrulega fram sem aukaafurð af mjög svipmiklum snjallsamningum, eða er önnur leið til draumsins um fullkomlega forritanlega peninga?
Short of avoiding protocols with highly expressive smart contracts and layer-2 tokens, users can avoid some of these risks by utilizing protocols that support Trúnaðarmál, like Liquid, that conceal transaction details. But unlike these platforms with more expressive scripting languages, Bitcoin lacks the ability to do things you would expect to be able to do with programmable money.
The Good: TradeOffs til forritanlegra peninga
When considering the evolution of smart contracts on Bitcoin the options we’re given are to (1) push the complexity off-chain, (2) cautiously integrate narrow or limited covenant functionalities, or (3) embrace the path of full expressivity. Let’s explore some of the proposals from each of these options.
(1) Nýtt skipulag fyrir samninga utan keðju: EINHVERFYRIR
Off-chain solutions, like the Lightning Network, aim to enhance Bitcoin’s scalability and functionality without burdening the mainchain, keeping transactions fast and fees low. This all sounds good so far.
SIGHASH_ANYPREVOUT (APO) er tillaga að nýrri tegund af opinberum lykli sem leyfir ákveðnar breytingar á viðskiptum jafnvel eftir að hún hefur verið undirrituð. Það einfaldar hvernig færslur eru uppfærðar, gerir færslum kleift að vísa til fyrri (UTXOs) auðveldara, sem gerir Lightning Network rásir hraðari, ódýrari, öruggari og einfaldari, sérstaklega við að leysa deilur.
Under the hood, APO is a new proposed type of sighash flag. Every Bitcoin transaction must have a signature to prove it’s legitimate. When creating this signature, you use a “sighash flag” to determine which parts of the transaction you’re signing. With APO a sender would sign all outputs and none of the inputs, to commit the outputs of the transaction, but not specifically which transaction the funds are going to come from.
APO enables Eltoo, allowing users to exchange pre-signed transactions off-chain. However APO may inadvertently introduce MEV by making transactions reorderable. As soon as you allow a signature that’s binding the transaction graph you have the ability to swap out transactions. Inputs can be swapped, as long as the new inputs are still compatible with the signature.
(2) Sáttmálar: CAT + CSFS og CTV
Sáttmálar myndu leyfa notendum að stjórna því hvert mynt getur færst, með því að setja hraðatakmarkanir eða setja sérstaka áfangastaði fyrir mynt í viðskiptum. Það eru tveir mismunandi flokkar sáttmála: endurkvæmir og óendurkvæmir.
Recursive covenants allow coins to continually return to covenants of the same type.Non-recursive covenants limit this control to the next transaction, requiring the entire future path of the coins to be defined upfront.CAT + CSFS is a covenant proposal that allows scripts to construct or define certain parts of a future transaction. CHECKSIGFROMSTACK (CSFS) verifies a signature against the data that OP_CAT constructed. By using CSFS to require the signature to match some dynamically constructed format from OP_CAT, we can define how these UTXOs can be spent in the future and create a recursive covenant, albeit clunkily.
OP_CHECKTEMPLATEVERIFY (CTV) er leið til að búa til óendurkvæma sáttmála. Í stað þess að skilgreina og sannreyna gegn ákveðnum hlutum viðskipta, takmarkar CTV hvernig hægt er að eyða fjármunum, án þess að tilgreina nákvæmlega næsta heimilisfang sem þeir verða að fara á. Það skilgreinir „sniðmát“ sem næsta viðskipti þarf að staðfesta.
One risk with recursive covenants might be possible to create a scenario where coins must follow a set of rules that repeat over and over, that get trapped in a loop without a way of getting out. Another is that, because covenants are transparent and self-executing they could open Bitcoin up to some of the MEV strategies we see on other chains.
Hverjar eru góðu fréttirnar hér?
Góðu fréttirnar eru þær að þessar tillögur kynna allar nýjar tjáningargetu!
Nú hvað er hámarks tjáning sem við getum fengið?
(3) Full tjáning: Einfaldleiki
Einfaldleiki is a blockchain-based programming language that differs from other scripting languages in that it is very low-level. It is not a language on top of Bitcoin Script or a new opcode within it, it’s an alternative to it. Theoretically, it’s possible to implement all covenant proposals within Simplicity, and implement many of the other contracts cypherpunks want from programmable money, but with less of the negative externalities of Ethereum.
Simplicity maintains Bitcoin’s design principle of self-contained transactions whereby programs do not have access to any information outside the transaction. Designed for both maximal expressiveness and safety, Simplicity supports formal verification and static analysis, giving users more reliable smart contracts.
Compare Simplicity to: (1) bitcoin covenant proposals and (2) scripting languages on other blockchains:
The covenant proposals on Bitcoin Script, though much simpler than Simplicity, lack the expressivity to handle fee estimation in Script, due to Bitcoin's lack of arithmetic functions. There is no way to multiply or divide, no conditionals or stack manipulations opcodes; it is also very hard to estimate a reasonable fee to be associated with a given contract or covenant. Users end up with spaghetti code, where 80% of their contract logic is dedicated to trying to determine what their fee rate should be. Making these covenant contracts super complicated and difficult to reason about.
The EVM has looping constructs which makes static analysis of gas usage very difficult. Whereas with Script or Simplicity, you can just count each opcode, or recursively add up the cost of each function. Because Simplicity has a formal model, you can formally reason about program behavior. You can't do this with Script even though you can do static analysis of resource usage.
Einfaldleiki myndi veita notendum mesta tjáningu, ásamt öðrum dýrmætum eiginleikum eins og kyrrstöðugreiningu og formlegri sannprófun. Notendur eru hvattir, þó ekki takmarkaðir, til að búa til snjalla samninga sem eru ónæmar fyrir MEV. Að auki getur sambland af mismunandi samningum saman leitt til MEV, jafnvel þó hver fyrir sig. Þetta táknar grundvallarviðskipti.
The idea of advancing Bitcoin’s smart contract functionality is undeniably promising and exciting. But it’s important to acknowledge that all these proposals carry some degree of MEV risk—albeit likely not to the extent that we see on other chains. As we think about bringing more programmable money to Bitcoin, there are questions we have to ask:
Can we build a protocol with zero MEV risk, or is this an unattainable ideal?Given the inherent risks of MEV in many proposals, what level of MEV risk is acceptable?And finally, what represents the simplest proposal that offers the greatest degree of expressivity?Hver tillaga hefur sína eigin kosti og galla. Hins vegar, óháð því hvaða stefnu við förum, ættum við alltaf að stefna að því að forgangsraða öryggi og halda uppi meginreglunni um valddreifingu.
Fyrir nákvæmar uppfærslur og frekari upplýsingar skaltu fylgjast með Blockstream rannsóknir 𝕏 fæða.
This is a guest post by Kiara Bickers. Opinions expressed are entirely their own and do not necessarily reflect those of BTC Inc or Bitcoin Tímarit.
Upprunaleg uppspretta: Bitcoin Tímarit