ZK Rollups and Proof Generation Bottlenecks

ZK proof generation is a sequential, memory-hard process. Throwing more CPUs at it yields minimal gains, creating a physical ceiling on throughput.

• Key Constraint: Memory bandwidth and latency, not core count.
• Current Fix: Specialized hardware (GPUs, FPGAs) from zkSync, Polygon zkEVM, and StarkWare.
• Future State: Dedicated ASICs, like those from Ingonyama, for 1000x efficiency gains.

Generating a validity proof is the single largest operational cost for a rollup, often exceeding data publication fees to Ethereum L1.

• Key Metric: Proving cost can be >50% of total transaction cost.
• Solution Vector: Recursive proofs (proof-of-proofs) to amortize cost, used by Scroll and Taiko.
• Economic Impact: High proving cost forces trade-offs between decentralization (prover set size) and user fees.

The capital and technical barriers to running a prover are immense, leading to centralized, permissioned prover networks controlled by the founding team.

• The Problem: Contradicts crypto's decentralized ethos; creates a single point of failure.
• Emerging Solution: Proof markets and decentralized prover networks, like Risc Zero's Bonsai and Espresso Systems.
• Endgame: Permissionless proving where anyone can sell compute, creating a competitive cost market.

ZK proving is a sequential, memory-hard process. Throwing more CPUs at it yields minimal gains. This is the core bottleneck limiting TPS and finality speed.

• Key Constraint: Memory bandwidth and latency, not raw compute.
• Current State: Leading L2s like zkSync Era and Starknet achieve ~50-100 TPS with finality in ~10-20 minutes.
• The Fix: Specialized hardware (ASICs, GPUs, FPGAs) from Ingonyama, Cysic, and Ulvetanna.

Centralized, permissioned provers create a single point of failure and cost. This undermines decentralization and keeps fees higher than theoretical minimums.

• The Risk: A single prover operator can censor or halt the chain.
• The Cost: Proving costs are a ~30-50% chunk of total sequencer operational expenses.
• The Solution: Proof markets and decentralized prover networks like Espresso Systems (shared sequencer) and Risc Zero (Bonsai network).

Not all ZK proofs are created equal. Circuit design and proof system choice (SNARKs vs. STARKs) dictate baseline performance and cost.

• Starkware (Cairo/STARKs): Prover-heavy, but scales better with large batches.
• zkSync/ZK Stack (Boojum/SNARKs): Faster prover time, but requires a trusted setup.
• The Frontier: Recursive proofs (Nova), custom VMs (Risc Zero), and proof aggregation (Polygon zkEVM, Scroll).

The endgame is breaking the sequential proving barrier. This is achieved through proof recursion and aggregation, turning many small proofs into one.

• How it Works: Prove blocks in parallel, then recursively aggregate them into a single proof for L1.
• Who's Doing It: Polygon zkEVM with its AggLayer, Scroll with its Roller network, and Risc Zero.
• Result: Near-instant finality for users, ~1-5 second proof times for the aggregated batch.

ASICs and high-end GPUs are inevitable. They directly attack the memory-hard bottleneck, offering order-of-magnitude improvements in cost and speed.

• The Players: Ingonyama (GPU-focused), Cysic (ASIC/FPGA), Ulvetanna (FPGA).
• The Impact: Projects like Aleo and Taiko are early adopters. Expect ~100x cost reduction and ~10x speedup vs. CPUs.
• The Caveat: Centralizes physical hardware production, creating a new trust layer.

Decouple proof generation from sequencing. Create a competitive market where provers bid to generate the cheapest, fastest proof for a batch.

• The Model: Similar to Ethereum's block builder market post-PBS.
• The Benefit: Drives costs to marginal hardware + energy, enhances censorship resistance.
• The Builders: Espresso Systems (shared sequencer with proof market), Risc Zero's Bonsai, and Nebra's proposed model.