A ZK Proof Can Be Hash-Based—and Still Carry a Quantum-Vulnerable Claim

The phrase “hash-based means post-quantum” is too broad for production ZK systems. A September 3 analysis from ZKM uses its Ziren zkVM to show why: a proof system can use hash-based commitments and still contain a separate component whose soundness depends on elliptic-curve security.

Ziren uses FRI for polynomial commitments and Poseidon2-based Merkle trees and transcripts. Those layers are not exposed to Shor’s algorithm in the same way as pairing-based cryptography. But ZKM says its audit of the broader GOAT Network stack found that Ziren’s offline memory-consistency argument used an elliptic-curve multiset hash. In that construction, memory values are mapped to curve points and accumulated in an elliptic-curve subgroup. The resulting soundness argument therefore carries a discrete-log assumption.

That distinction matters because the proof does not merely commit to data. It proves a relation about the data. If the relation includes an elliptic-curve assertion, wrapping it in a hash-based commitment or a hash-based zkVM does not remove the elliptic-curve assumption. ZKM gives the same warning for Groth16 verification placed inside a garbled circuit, witness encryption tied to a pairing equation, and a hypothetical proof that a BLS aggregate signature verified. In each case, the wrapper may be hash-based while the statement remains quantum-vulnerable.

The practical lesson for ICP builders is compositional review. When a canister, bridge, identity service, or proof relay accepts a ZK proof, the audit should inventory more than the headline proof system. It should identify the commitment scheme, transcript hash, lookup or memory argument, signature checks, curve operations, and any recursive or cross-chain wrapper. This is an engineering implication of the sources, not a claim that ICP itself is affected by the Ziren finding.

ZKM describes two possible directions for replacing the memory check. One is an additive multiset digest in the LtHash family, which would move the assumption toward lattice-based security. The other is a LogUp-GKR memory argument using field arithmetic and FRI commitments, which ZKM says could remove the remaining non-hash assumption rather than exchange it for another one.

There is an important qualification: ZKM says the choice has not been made. It also says the current LtHash branch relies on a random-matrix heuristic instead of a completed reduction. That prototype should therefore be understood as an exploration of a possible assumption change, not as a finished post-quantum security result.

Ethereum’s current post-quantum documentation makes the broader context clear: many pairing-based SNARKs remain vulnerable to quantum attacks, while STARK-style systems rely on hash functions instead of elliptic curves. But “hash-based” still describes a stack, not a universal security certificate. The security claim must be traced through every relation the proof verifies.

For ICP teams evaluating ZK integrations today, the checklist is straightforward: write down the exact theorem, list every cryptographic assumption beneath it, separate wrapper security from statement security, and require a written reduction for any proposed replacement. That discipline makes a proof’s trust boundary reviewable before it becomes infrastructure.