Why the 'Write Once, Prove Anywhere' Dream for ZK Circuits Is Stalling

The portability promise is broken. Zero-knowledge proofs are not fungible assets; a proof generated for a zkEVM like Scroll is useless for a zkVM like RISC Zero without a costly, custom verification circuit.

Proving systems are tribal. StarkWare's STARKs and Zcash's Halo2 use different cryptographic backends, forcing developers to choose a proving ecosystem rather than a universal toolkit.

The cost of verification is prohibitive. Deploying a new verification smart contract for each target chain, as done by Polygon zkEVM and zkSync Era, creates unsustainable overhead for cross-chain applications.

Evidence: No major L2 or appchain uses a single ZK proof to verify state across Ethereum, Arbitrum, and Solana. The interoperability standard remains a collection of bespoke bridges, not a shared proof layer.

Proving systems are not fungible. A circuit written for zkSNARKs (Groth16, Plonk) cannot run on a zkSTARK prover without a full rewrite. This creates vendor lock-in at the cryptographic layer, not just the execution layer.

Standardization efforts are fragmented. The RISC Zero zkVM and SP1 use different instruction sets. Polygon zkEVM and Scroll implement divergent EVM compatibility layers. Each defines its own intermediate representation (IR).

The economic incentive is misaligned. Teams like StarkWare (Cairo) and Matter Labs (Boojum) optimize for their own L2 dominance. A universal standard dilutes their competitive moat and ecosystem control.

Evidence: No major L2 has switched its core proving system post-launch. Arbitrum's move to Stylus introduced a new VM, not a portable circuit format. The Ethereum Foundation's PSE works on multiple, parallel ZK toolchains.

Hardware specialization creates lock-in. The 'write once, prove anywhere' promise of ZK circuits assumes a homogeneous proving environment. In reality, specialized hardware like the zkVM accelerators from Cysic or Ulvetanna delivers 10-100x speedups, but these gains are not portable across different hardware architectures.

Performance is the new moat. Protocols like zkSync Era and Polygon zkEVM optimize for their specific proving stacks. A circuit optimized for a GPU-based prover will run suboptimally on an FPGA or ASIC system. This performance divergence makes circuit portability a theoretical ideal, not a practical reality.

The ecosystem fragments. Instead of a unified ZK landscape, we see proprietary proving stacks emerging. A circuit written for RISC Zero's zkVM cannot leverage the acceleration of a Succinct Labs prover without significant, costly re-engineering, defeating the purpose of interoperability.

Evidence: The proving time for a complex zkEVM batch on commodity hardware is minutes; on a dedicated FPGA cluster from a firm like Ingonyama, it drops to seconds. This orders-of-magnitude gap is the economic incentive that breaks the portability model.

The LLVM analogy is flawed. The dream of a universal ZK-IR (Intermediate Representation) like LLVM ignores a critical difference: LLVM targets commodity CPUs, while ZK circuits target specialized, non-standardized proving hardware like RISC Zero's zkVM or Succinct's SP1.

Hardware dictates the IR. Prover companies like Ingonyama (focused on GPU acceleration) and Ulvetanna (FPGA/ASIC) optimize for specific instruction sets. A common IR forces a lowest-common-denominator approach, sacrificing the performance gains that justify custom hardware investment.

Incentives are misaligned. A universal IR creates a commoditized proving layer, eroding the competitive moat for hardware builders. This is why projects like RISC Zero maintain proprietary toolchains; their ISA is their product.

Evidence: The fragmentation persists. No major ZK-rollup (e.g., zkSync, StarkNet, Scroll) uses a shared compilation target. Each has a bespoke circuit compiler tuned for its specific prover backend and security assumptions, proving the market rejects a one-size-fits-all solution.