Why Most ZK-Rollup Circuits Are Cryptographically Unsound

Most zkEVMs and zkRollups rely on a trusted ceremony (e.g., Groth16) for their SNARKs. This creates a persistent, hidden backdoor: if the initial toxic waste is not destroyed, the entire system can be forged. The security model regresses from cryptographic to social trust.

• Single Point of Failure: Compromise of one ceremony participant invalidates all proofs.
• Permanent Risk: The threat is perpetual, not just during setup.
• Audit Opaqueness: Ceremony correctness is virtually impossible to verify post-hoc.

Circuit constraints operate over finite fields, not arbitrary-precision integers. Unchecked arithmetic in custom opcodes or business logic can silently wrap, creating soundness gaps where invalid states are 'proven' valid. This is a compiler and circuit-writer problem, not a proof system flaw.

• Silent Validation: The circuit accepts a wrapped, incorrect computation as correct.
• Compiler Dependency: High-level language (Cairo, Noir, Circom) compilers must be bug-free.
• State Corruption: Can lead to invalid token minting or balance corruption.

Circuits needing external data (e.g., price feeds, block headers) rely on oracles fed by off-chain actors. The proof only verifies the data was signed, not that it's temporally correct or logically consistent. An adversarial sequencer can feed stale or manipulated data, breaking application logic while the proof remains valid.

• Proof/Data Decoupling: Soundness of the proof != soundness of the execution.
• Sequencer Power: Centralizes trust in the data provider layer.
• Systemic Risk: Affects DeFi protocols like Aave or Compound built on the rollup.

Most ZK-Rollups rely on perpetual trusted setups (e.g., Groth16) or complex multi-party ceremonies. A single compromised participant can forge proofs, invalidating the entire chain's state. This reintroduces the very trust assumption ZKPs were meant to eliminate.

• Critical Flaw: Ceremony integrity is a social, not cryptographic, guarantee.
• Real Risk: Historical leaks in Zcash's Powers of Tau ceremony highlight the threat.

Circuit constraints are written in high-level languages (Circom, Cairo) and compiled to R1CS/Plonkish. Silent integer overflows in constraint systems can create undetectable backdoors, allowing malicious provers to generate valid proofs for false statements.

• Root Cause: Finite field arithmetic differs from integer math; developers often miss edge cases.
• Example: The zkEVM parity bug where 0 != 0 due to a field underflow.

Circuits for DeFi (e.g., DEX, lending) require external price feeds. Integrating these oracles on L2 creates a critical centralization vector. A malicious sequencer can feed stale or manipulated data into the proof, causing mass liquidations or arbitrage losses.

• Architectural Flaw: ZK validity doesn't guarantee data freshness or correctness.
• Systemic Risk: Affects zkSync Era, StarkNet, and Polygon zkEVM DeFi ecosystems.

To scale, L2s use recursive proofs (proofs of proofs). However, aggregation circuits are notoriously complex and introduce new attack surfaces. A bug in the aggregation verifier can invalidate the entire proof chain, making fraud detection impossible.

• Compounding Risk: A single error propagates through all subsequent state updates.
• State of Art: Nova and Plonky2 aim for safer recursion but are still experimental.

Generating ZK proofs requires specialized hardware (GPU/FPGA/ASIC). This creates prover centralization, as only well-capitalized entities can afford the setup. A cartel of provers could censor transactions or collude to halt the chain.

• Economic Reality: Contradicts decentralized sequencing narratives.
• Evidence: Scroll and Polygon zkEVM prover networks are controlled by few entities.

The path forward requires mathematically verified circuits and transparent proof systems. Projects like StarkWare (with its STARK proofs, no trusted setup) and RISC Zero (using the RISC-V ISA for verifiability) are leading the shift. Audits must move from manual review to automated formal verification tools.

• Mandatory: Use of PLONK with Universal Trusted Setup or STARKs.
• Tooling Shift: Adoption of Picus, VeriSolid for circuit verification.

Ceremonies like Groth16's Perpetual Powers of Tau are only secure if a single participant is honest. Most projects fork a ceremony without understanding the multi-party computation (MPC) transcript's provenance or age. An old, poorly audited ceremony is a single point of failure for $1B+ in bridged assets.

• Risk: Compromised secret parameters invalidate all proofs.
• Action: Demand proof of ceremony recency and participant diversity.

Teams test circuits with benign, self-generated proofs. They never test against a malicious prover attempting to generate a valid proof for an invalid state transition. This misses logic bugs in custom constraints (e.g., token arithmetic) that a white-hat prover wouldn't trigger.

• Risk: Soundness failure allowing invalid state roots.
• Action: Implement adversarial proof generation in your devnet, fuzzing invalid inputs.

The on-chain verifier is often a black-box library (e.g., snarkjs output) with zero upgradeability controls or emergency halts. If a bug is found in the verification logic or underlying elliptic curve precompile, the entire rollup is hostage.

• Risk: Irreversible cryptographic bug bricks the chain.
• Action: Wrap verifier in a timelock-controlled proxy with a security council kill-switch.

To achieve faster finality, teams implement recursive proof aggregation (e.g., Plonky2, Nova) without benchmarking the prover time/cost trade-off. The cryptographic overhead for recursion often negates the L1 gas savings, making a simpler, single-proof system more efficient.

• Risk: 10x higher prover costs for marginal finality improvement.
• Action: Model total cost (L1 gas + prover AWS) before committing to a stack.

Projects like Espresso Systems use TEEs (Intel SGX) for faster proving, outsourcing security to hardware manufacturers and remote attestation services. This introduces supply-chain attacks and side-channel vulnerabilities, breaking the trustless premise of ZK-Rollups.

• Risk: Centralized failure mode outside cryptography.
• Action: Treat TEEs as a performance optimization, not a security foundation.

A perfectly sound ZK proof is worthless if the input data (calldata, blobs) is unavailable. Teams focus on the circuit while treating Ethereum DA or Celestia as a black box. If the DA layer censors or loses the rollup's data, the state cannot be reconstructed, making proofs unverifiable.

• Risk: Liveness failure via DA dependency.
• Action: Implement multi-DA fallbacks and monitor attestations.