Auditability is the critical trade-off. Every ZK-EVM design, from Polygon zkEVM to Scroll, makes architectural choices that directly impact how easily developers and users can verify its correct operation.
zk-rollups-the-endgame-for-scaling
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Auditability Is the Critical Trade-off in ZK-EVM Design
The pursuit of EVM equivalence in ZK-rollups creates an auditability crisis. Opaque proof systems and complex circuit logic make formal verification exponentially harder than auditing traditional smart contracts, introducing systemic risk.
introduction
THE TRADE-OFF
Introduction
ZK-EVM design is a direct optimization problem between performance and the ability to verify correctness.
Performance sacrifices transparency. Type 1 (fully Ethereum-equivalent) ZK-EVMs like Taiko prioritize auditability but generate slower proofs, while Type 4 (high-level language compilers) like zkSync Era optimize for speed by obscuring the execution trace.
The core tension is between equivalence and abstraction. A Type 1 ZK-EVM's bytecode-level compatibility makes its state transitions directly verifiable against Ethereum's spec, a property Type 3 and Type 4 systems intentionally forfeit for efficiency.
Evidence: Starknet's move from a Cairo-native VM (Type 4) to a new design with a Solidity compiler front-end is a direct concession that developer auditability drives adoption over raw theoretical throughput.
thesis-statement
THE ARCHITECTURAL DILEMMA
The Core Trade-off: Performance vs. Provable Security
ZK-EVM design forces a choice between raw execution speed and the cryptographic integrity of the state transition proof.
The central trade-off is auditability. A ZK-EVM must prove the correct execution of EVM bytecode, but the proving overhead varies drastically based on the level of EVM equivalence. Type 1 ZK-EVMs like Taiko prove every EVM opcode directly, creating a high-fidelity audit trail but incurring massive proving costs and slower finality.
Performance requires abstraction. Type 2/3 ZK-EVMs like zkSync Era and Polygon zkEVM modify the execution environment for efficiency, trading some bytecode-level equivalence for faster, cheaper proofs. This creates a trust boundary where the system's correctness depends on the soundness of these custom circuits, not just the ZK proof itself.
The counter-intuitive insight is that 'faster' often means 'less proven'. A system claiming 100k TPS likely proves a high-level summary, not each opcode. This mirrors the security spectrum in cross-chain bridges, where fast, cheap bridges like Stargate use optimistic models, while slower, provable systems like Succinct Labs' Telepathy prioritize cryptographic verification.
Evidence: Proving time is the metric. A Type 1 proof for a full Ethereum block takes hours on specialized hardware. A Type 4 proof for a compiled application, as used by StarkNet with its Cairo VM, generates proofs in minutes. The industry standardizes on proof aggregation and recursive proofs to amortize this cost, but the fundamental trade-off remains.
key-trends
THE ZK-EVM TRILEMMA
The Three Pillars of the Auditability Crisis
Zero-knowledge proofs trade off auditability for scalability and privacy, creating a fundamental crisis for protocol security and governance.
01
The Problem: Opaque State Transitions
A ZK-EVM's state transition logic is locked inside a proving key. Auditors can't directly review the rules governing $10B+ TVL; they must trust the key's generation ceremony.
- Key Risk: A malicious or buggy circuit is cryptographically enforced.
- Key Consequence: Protocol upgrades become a 'trust-me' event, breaking decentralized governance.
0 Lines
Auditable Code
1 Ceremony
Single Point of Trust
02
The Problem: Unverifiable Prover Centralization
Generating ZK proofs is computationally intensive, leading to prover centralization. The sequencer/prover becomes a ~500ms black box.
- Key Risk: Censorship and MEV extraction are invisible and unprovable.
- Key Consequence: Liveness depends on a few entities, recreating Web2 cloud dependencies.
~3-5
Major Provers
500ms
Black Box Latency
03
The Problem: The Data Availability Black Hole
Validity proofs require the underlying data to be available for reconstruction. Ethereum-calldata is expensive, pushing rollups to alternative DA layers like Celestia or EigenDA.
- Key Risk: If the chosen DA layer fails, the ZK proof is meaningless; the chain halts.
- Key Consequence: Security is fragmented across multiple trust layers, breaking the 'Ethereum-as-a-court' model.
-90%
DA Cost Save
N+1 Layers
Trust Assumptions
THE TRUST-COMPUTE TRADEOFF
ZK-EVM Auditability Spectrum: A Comparative Analysis
Compares the auditability, trust assumptions, and performance characteristics of different ZK-EVM design philosophies, from Type 1 to Type 4.
| Auditability & Trust Metric | Type 1 (Fully Equivalent) | Type 2 (EVM Equivalent) | Type 3 (Almost EVM Equivalent) | Type 4 (High-Level-Language Equivalent) |
|---|---|---|---|---|
Ethereum Node Verifiability | ||||
Auditor Required to Understand ZK Circuits | ||||
Auditor Required to Understand Custom Precompiles | ||||
Prover Time (Relative to EVM Execution) | 1000-5000x | 100-500x | 10-100x | 1-10x |
Proof Size per Tx (Approx.) | ~500 KB | ~50 KB | ~10 KB | < 5 KB |
Trust Assumption on Circuit Correctness | None (Ethereum Consensus) | ZK Circuit Logic | ZK Circuit + Custom Precompile Logic | ZK Circuit + Compiler Toolchain |
Primary Audit Surface | Ethereum Client Code | ZK Circuit Code | ZK Circuit + Precompile Code | ZK Circuit + Compiler IR |
Example Implementations | Taiko | Polygon zkEVM, Scroll | zkSync Era Legacy, Linea | zkSync Era Boojum, Starknet (Cairo VM) |
deep-dive
THE TRUST ASSUMPTION
Why Circuit Audits Are an Order of Magnitude Harder
The cryptographic correctness of a ZK-EVM is a single point of failure that requires a fundamentally different, more intensive audit process.
Auditing cryptographic circuits is not code review. It is verifying mathematical proofs of computational integrity. A single bug in a circuit, like the one exploited in the zkSync Era Boojum upgrade, invalidates the entire system's security.
The audit surface explodes. A traditional EVM audit checks opcode logic and state transitions. A ZK-EVM audit must also verify the circuit compiler (like Circom or Halo2), the prover implementation, and the trusted setup ceremony, as seen in Polygon zkEVM's Plonky2 stack.
Counter-intuitively, more abstraction increases risk. High-level ZK toolchains (e.g., Noir, RISC Zero) simplify development but create opaque abstraction layers. Auditors must now trust the entire toolchain's correctness, not just the application logic.
Evidence: The Hermez network (now Polygon zkEVM) required over 12 person-months for its initial circuit audit. A standard Solidity contract audit typically requires 2-4 weeks.
counter-argument
THE FLAWED PREMISE
The Optimist's Rebuttal (And Why It's Wrong)
The argument for maximal equivalence ignores the operational reality that auditability is the primary constraint for production systems.
Auditability is the bottleneck. Optimists argue equivalence is the only goal, but ZK-EVM performance is irrelevant if you cannot debug a failed proof. A system like Scroll or Polygon zkEVM prioritizes prover transparency and developer tooling over byte-for-byte parity.
Production systems require observability. A Type 1 zkEVM like Taiko's offers perfect equivalence but creates a black-box prover. When a transaction fails, developers face an inscrutable proof instead of a readable EVM trace, increasing mean time to resolution.
The trade-off is explicit. You choose between Ethereum's auditability model and ZK's trust model. Projects like Starknet accept this, building new tooling for their Cairo VM. The false promise is that you get both for free.
Evidence: No major Type 1 zkEVM runs mainnet. The operational complexity of debugging a ZK-circuited Geth client is prohibitive. Type 2/3 zkEVMs from Scroll and Polygon zkEVM dominate because they optimize for the developer, not the spec.
risk-analysis
AUDITABILITY TRADE-OFFS
The Bear Case: Systemic Risks of Opaque Rollups
ZK-EVMs optimize for performance, but the resulting complexity creates systemic risk by obscuring state transitions from users and validators.
01
The Problem: Unverifiable State Growth
Users cannot independently verify the rollup's state without re-executing every transaction. This creates a single point of failure in the sequencer and prover.\n- Reliance on Trust: Users must trust the posted ZK proof is valid and corresponds to the correct state diff.\n- Data Unavailability Risk: If the sequencer withholds transaction data, the proof is meaningless, a risk highlighted by EigenDA and Celestia designs.
~100K TPS
Opaque Throughput
1
Verifiable Entity
02
The Solution: Aggressive Proof Recursion
Projects like Polygon zkEVM and zkSync use recursive proofs to compress days of activity into a single proof for Ethereum. This is the technical hedge against opacity.\n- Finality Anchor: A single on-chain proof verifies millions of transactions, making censorship economically irrational.\n- Cost Amortization: Massive computation is offloaded, but the ~20 minute finality delay is the trade-off for this cryptographic guarantee.
1 Proof
For 24H of TXs
~20 Min
Finality Delay
03
The Problem: Centralized Prover Control
High-performance provers (e.g., Risc Zero, SP1) are hardware-intensive, leading to prover centralization. A malicious or faulty prover can halt the chain or, worse, produce a valid proof for an invalid state.\n- Hardware Moats: Specialized hardware creates centralization vectors similar to early PoW mining.\n- Liveness Risk: If the dominant prover fails, the chain stops until proofs can be generated elsewhere, a risk Espresso Systems is tackling with decentralized sequencing.
ASIC/GPU
Prover Hardware
0
Fault Tolerance
04
The Solution: Multi-Prover & Fraud Proof Hybrids
Arbitrum Nova and Polygon Avail demonstrate hybrid models. The bear case is mitigated by not putting all trust in one cryptographic system.\n- Defense in Depth: Use a ZK proof for speed, but fall back to a fraud proof (like Optimism) if a fault is suspected.\n- Prover Markets: Architectures like AltLayer's restaked rollups envision a competitive market for proof generation, reducing centralization risk.
2+ Systems
Safety Layers
7 Days
Challenge Window
05
The Problem: Upgradability as a Backdoor
Most rollups, including zkEVMs, have upgradeable contracts controlled by a multisig. This creates a systemic escape hatch that invalidates all cryptographic guarantees.\n- Admin Key Risk: A 4/7 multisig can change prover keys, verifier contracts, or steal funds, a risk underscored by the Starknet upgrade process.\n- Temporary Centralization: The promise of future decentralization is the industry's biggest credibility deficit, as seen in early Optimism and Arbitrum.
4/7 Multisig
Typical Control
$10B+ TVL
At Risk
06
The Solution: Immutable Verifiers & Governance Minimization
The endgame is a truly immutable verifier contract on Ethereum. This is the only way to close the trust gap. Scroll and Taiko are architecting toward this.\n- Credible Neutrality: Once frozen, the rules cannot change, making the L2 a true extension of Ethereum's security.\n- Slow is Fast: This requires exhaustive audits and formal verification, delaying feature launches but providing unshakable finality.
0
Admin Keys
L1 Security
Final Guarantee
future-outlook
THE TRADE-OFF
The Path Forward: Auditable Primitives, Not Opaque Monoliths
The core design choice for ZK-EVMs is between a monolithic, optimized prover and a modular, auditable stack.
Auditability is the constraint. A ZK-EVM's security depends on the correctness of its circuit. A monolithic design like Scroll's creates a single, complex circuit that is fast but opaque and unauditable. This concentrates risk.
Modular primitives are the alternative. Projects like RISC Zero and SP1 build general-purpose ZK-VMs. Developers compose them with open-source compilers like zkLLVM to create auditable, specialized circuits. This trades raw performance for verifiable security.
The market will bifurcate. High-frequency DeFi on L2s will use monolithic provers for speed. Sovereign chains and app-chains will adopt modular stacks for sovereignty and auditability, mirroring the Cosmos vs. Ethereum execution layer split.
Evidence: Polygon zkEVM's circuit is ~500k lines of custom code, a massive audit surface. In contrast, a Starknet app-chain using Cairo and a shared prover network relies on a single, battle-tested virtual machine.
takeaways
AUDITABILITY TRADE-OFFS
TL;DR for Protocol Architects
ZK-EVM design is a spectrum between performance and the ability to verify correctness. This is the core architectural decision.
01
The Type 1 (Ethereum-Equivalent) Trap
Perfect auditability via bytecode equivalence, but at a massive performance cost. This is the Polygon zkEVM and Scroll approach.
- Key Benefit: 100% EVM Opcode Coverage means any Ethereum tool works.
- Key Cost: ~5-10x slower proving times and higher costs versus optimized designs.
100%
EVM Equiv
5-10x
Slower Proving
02
The Type 4 (Language-Level) Gambit
Sacrifices direct bytecode auditability for radical performance gains. This is the zkSync Era and Starknet model.
- Key Benefit: ~50-80% cheaper user transactions due to custom VM optimizations.
- Key Risk: Compiler Trust Assumption; you must trust their Solidity→zk-ASM compiler, a new attack surface.
-50%
Tx Cost
Compiler
Trust Assumption
03
Type 2.5: The Pragmatic Middle Ground
Balances auditability with gas efficiency by modifying EVM gas costs and state layout. This is the core Polygon zkEVM and emerging design pattern.
- Key Benefit: ~30% gas savings via optimized storage proofs and precompiles.
- Key Trade-off: Non-equivalent gas metering breaks precise cost predictability, requiring dApp adjustments.
-30%
Gas Cost
Modified
Gas Model
04
The Prover Centralization Dilemma
High-performance proving (e.g., Risc Zero, SP1) creates a hardware arms race, risking centralization.
- Key Risk: Prover becomes a trusted party if the network relies on a few specialized operators.
- Key Mitigation: Proof Aggregation (like Espresso Systems) and ASIC-resistant designs are critical for decentralization.
Hardware
Arms Race
Proof Agg
Solution
05
Auditability is a Liquidity Metric
The easier a chain is to audit, the lower the risk premium for capital. This directly impacts TVL and composability.
- Key Insight: Type 1 chains attract institutional capital and complex DeFi (e.g., MakerDAO).
- Key Insight: Type 4 chains win on high-volume, low-value transactions (e.g., gaming, social).
TVL
At Risk
DeFi
Composability
06
The Future is Multi-Proof
No single ZK-EVM type will dominate. The end-state is application-specific proof systems (like Aztec for privacy) connected via interoperability layers.
- Key Trend: zkRollups will specialize, using shared sequencing (e.g., Espresso, Astria) and bridges (e.g., LayerZero, Axelar) for liquidity flow.
- Architectural Imperative: Design dApps for portability across proof regimes.
App-Specific
Proofs
Shared Seq
Layer
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