By Bitcoin Ajakiri - 3 kuud tagasi - lugemisaeg: 11 minutit
Miner Extractable Value (MEV) ja programmeeritav raha: hea, halb ja inetu
Tuum 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?
Mis on MEV?
Töötõendamise süsteemides "Kaevandaja kaevandatav väärtus"(ML) on termin, mis kirjeldab kasumit, mida kaevandajad saavad teenida, manipuleerides sellega, kuidas tehinguid nende kaevandatavates plokkides prioriseeritakse, välistatakse, ümber korraldatakse või muudetakse. Kuid pärast Ethereumi versiooniuuendust versioonile Ethereum 2.0, mis viis võrgu panuse tõestamise süsteemile, on MEV-i kontseptsioon saanud uue nime ja nüüd nimetatakse seda panuse tõestamise süsteemides "maksimaalseks ekstraheeritavaks väärtuseks". Selles kontekstis on kaevurite asemel plokipakkujatel – kes on valideerijad – võimalus see väärtus välja võtta.
Kaevuritel (või Ethereumi validaatoritel) on nendes võrkudes eriline roll, mis kinnitab tehinguid plokkidena. Nende positsioon seab nad teistest kasutajatest sammu võrra ette ja võimaldab neil kindlaks teha tehingute lõplik järjekord ahelas. Plokis tellitakse tehingud tavaliselt kõrgeimate tasudega ülaosas, kuid aeg-ajalt avanevad võimalused, mis võimaldavad kaevuritel lisakasum tehingute järjekorda strateegiliselt enda huvides muutes.
Võiksite mõelda, mis kahju on sellest, kui lasete kaevuritel teenida veidi lisakasumit? Mured hakkavad esile kerkima alles siis, kui mõned neist kaevandajatest, kellel on täiustatud analüüsivõimalused ja võimsam andmetöötlus, suudavad tuvastada ja kasutada MEV kasumivõimalusi teistest tõhusamalt.
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.
Miks me tahame programmeeritavat raha?
Ajalooliselt 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?
Kas ilmekamad nutikamad lepingud stimuleerivad automaatselt rohkem MEV-stsenaariume?
MEV-i soodustavad mitmed tegurid: (1) mempooli läbipaistvus, (2) nutika lepingu läbipaistvus ja (3) nutika lepingu väljendusvõime. Kõik need tegurid avavad MEV jaoks uusi kanaleid, me vaatame siin kõik üle.
Halb: (1) Mempooli läbipaistvus
nagu 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.
Võrrelge seda Ethereumiga, kus on mõned kõige keerukamad mitme varaga tehingud, mis toimuvad avalikel detsentraliseeritud börsidel (DEX). Ametlikult on Ethereumi blokeerimisaeg 15 sekundit, kuid suure mempooli liikluse perioodidel võivad kohese ploki kaasamise nõutavad gaasitasud kergesti ületada saja dollari piiri. Selle tulemusena ootavad madalamate tasudega tehingud minuteid või isegi tunde, enne kui need plokki kaasatakse. See võib pikendada nende alatute eesrindlike võimaluste akent, mis on Ethereumis juba enam levinud, kuna 2. kihi žetoonides on märkimisväärne väärtus.
Halb: (2) arukas lepingu läbipaistvus
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.
Kuid 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.
Inetu: (3) Nutikas lepingu väljendusvõime
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.
Mõned neist MEV-strateegiatest kehtivad nii kihi 1 kui ka 2 jaoks.
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.Siis on teatud strateegiad unikaalsed 2. kihi žetoonide ja nutikate lepingute jaoks.
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.Lepingute keerukus aitab oluliselt kaasa MEV-ga seotud väljakutsetele.
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.Osa probleemist seisneb siin selles, et 2. kihile ehitatud žetoonide ja dAppide loodud koguväärtus ületab sageli 1. kihi plokiahela algvara väärtust, mis kahjustab validaatorite stiimulit valida ja kinnitada tehinguid puhtalt tasude alusel.
Asja teeb hullemaks see, et paljud neist võimalustest ei piirdu rangelt võrguvalidaatoritega. Teised võrgus osalejad, kellel on MEV-skannimisbotid, võivad samade võimaluste pärast konkureerida, põhjustades võrgu ummikuid, tõstes gaasitasusid ja suurendades tehingukulusid. See stsenaarium tekitab negatiivse välismõju võrgule ja selle kasutajatele, keda kõiki mõjutab kõrgemate tehingutasude hind, kuna kett muutub vähem tõhusaks ja kulukamaks. DeFi MEV on nii levinud, et kasutajad on seda peaaegu aktsepteerinud kui nähtamatut maksu kõigile võrgus osalejatele.
Kas need MEV-võimalused tekivad loomulikult ülimalt väljendusrikaste nutikate lepingute kõrvalproduktina või on täiesti programmeeritava raha unistusele alternatiivne tee?
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 Konfidentsiaalsed tehingud, 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.
Hea: kompromissid programmeeritavale rahale
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) Ketiväliste lepingute uus struktuur: ANYPREVOUT
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) on ettepanek uut tüüpi avaliku võtme jaoks, mis võimaldab tehingut teatud muudatusi teha ka pärast selle allkirjastamist. See lihtsustab tehingute värskendamist, võimaldades tehingutel hõlpsamini viidata eelmistele (UTXO-dele), muutes Lightning Networki kanalid kiiremaks, odavamaks, turvalisemaks ja arusaadavamaks, eriti vaidluste lahendamisel.
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) Lepingud: CAT + CSFS ja CTV
Lepingud võimaldaksid kasutajatel kontrollida, kus mündid võivad liikuda, kehtestades tehingus kiiruspiirangud või määrates müntide jaoks konkreetsed sihtkohad. Lepingutel on kaks erinevat kategooriat: rekursiivne ja mitterekursiivne.
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) on viis mitterekursiivsete lepingute loomiseks. Selle asemel, et määratleda ja kontrollida tehingu konkreetseid osi, piirab CTV raha kulutamist, määramata täpselt järgmist aadressi, kuhu nad peavad minema. See määratleb "malli", mille järgmine tehing peab kinnitama.
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.
Mis on siin hea uudis?
Hea uudis on see, et kõik need ettepanekud lisavad uut väljendusrikkust!
Kui suur on maksimaalne väljendusvõime, mida me saame?
(3) Täielik väljendusvõime: lihtsus
Lihtsus 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.
Lihtsus tagaks kasutajatele kõrgeima väljendusrikkuse koos muude väärtuslike funktsioonidega, nagu staatiline analüüs ja formaalne kontrollimine. Kasutajad on motiveeritud, kuigi mitte piiratud, koostama nutikaid lepinguid, mis on MEV-le vastupidavad. Lisaks võib erinevate lepingute kombinatsioon kaasa tuua MEV, isegi kui nad seda eraldi ei tee. See kujutab endast fundamentaalset kompromissi.
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?Igal ettepanekul on oma eelised ja puudused. Kuid hoolimata sellest, millise suuna me võtame, peaksime alati seadma esikohale turvalisuse ja järgima detsentraliseerimise põhimõtet.
Üksikasjalike värskenduste ja lisateabe saamiseks hoidke silma peal Blockstream Research 𝕏 sööta.
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 Ajakiri
Algne allikas: Bitcoin Ajakiri