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Proof Aggregation Service Deep Dive

Architecture Overview

The Proof Aggregation Service consists of three main components that work together to aggregate user proofs and submit them on-chain.

┌──────┐    ┌───────────────────────────────┐    ┌─────────────┐
│      │ 1  │ AggregationModePaymentService │ 2  │   Payments  │
│      │--->│           (Contract)          │--->│    Poller   │
│      │    └───────────────────────────────┘    └─────┬───────┘
│      │                                               │
│      │                                             3 │
│      │                                               v
│      │    ┌───────────────┐  5                ┌──────────────┐    ┌───────────────────────────────┐
│ User │ 4  │    Gateway    │------------------>│  PostgreSQL  │    │ AlignedProofAggregationService│
│      │--->│               │                   │      DB      │    │           (Contract)          │
│      │    └───────────────┘                   └──────────────┘    └───────────────────────────────┘
│      │                                               ^                          ^
│      │                                             6 │                          │
│      │                                               │                        7 │
│      │                                        ┌─────────────┐                   │
│      │                                        │    Proof    │-------------------┘
│      │                                        │  Aggregator │
└──────┘                                        └─────────────┘
  1. User deposits ETH into AggregationModePaymentService contract to get quota.
  2. Payments Poller monitors the contract for deposit events.
  3. Payments Poller updates user quotas in the database.
  4. User submits proofs to the Gateway.
  5. Gateway validates and stores proofs in the database.
  6. Proof Aggregator fetches pending proofs from the database.
  7. Proof Aggregator aggregates proofs in the zkVM and submits to AlignedProofAggregationService contract.

Supported Proof Types

The aggregation service currently supports:

  • SP1: Aggregates proofs of type Compressed

Proof Commitment

The proof commitment is a hash that uniquely identifies a proof. It is defined as the keccak of the proof public inputs + program ID:

  • For SP1: The commitment is computed as: keccak(proof_public_inputs_bytes || vk_hash_bytes)

Multilayer Aggregation

To scale aggregation without exhausting zkVM memory, aggregation is split into two programs:

                        User Proofs (n per chunk)
                                  │
          ┌───────────────────────┼───────────────────────┐
          │                       │                       │
          ▼                       ▼                       ▼
   ┌─────────────┐         ┌─────────────┐         ┌─────────────┐
   │   Chunk 1   │         │   Chunk 2   │         │   Chunk N   │
   │  Aggregator │         │  Aggregator │         │  Aggregator │
   └──────┬──────┘         └──────┬──────┘         └──────┬──────┘
          │                       │                       │
          │    Aggregated Proofs + Merkle Roots           │
          │                       │                       │
          └───────────────────────┼───────────────────────┘
                                  │
                                  ▼
                        ┌─────────────────┐
                        │     Chunk       │
                        │   Aggregator    │
                        └────────┬────────┘
                                 │
                                 ▼
                        ┌─────────────────┐
                        │  Final Proof +  │
                        │   Merkle Root   │
                        └─────────────────┘

  1. User Proof Aggregator Processes chunks of n user proofs. Each run creates an aggregated proof that commits to a Merkle root of the user proofs inputs. This step is repeated for as many chunks as needed. Usually each chunk contains 256 proofs but it can be lowered based on the machine specs.

  2. Chunk Aggregator Aggregates all chunk-level proofs into a single final proof. It receives:

    During verification, it checks that each chunk's committed Merkle root matches the reconstructed root to ensure input correctness. The final Merkle root, representing all user proofs commitments, is then committed as a public input.

Verification

Once aggregated, the proof is sent to Ethereum and verified via the AlignedProofAggregationService contract. The contract invokes verifySP1 which receives:

  • The public inputs
  • The proof binary

The program ID is hardcoded in the contract to ensure only trusted aggregation programs (chunk_aggregator) are accepted.

If verification succeeds, the new proof is added to the aggregatedProofs map in contract storage.

Proof Inclusion Verification

To verify a user's proof on-chain, the following must be provided:

  • The proof bytes
  • The proof public inputs
  • The program ID (vk hash)
  • A Merkle proof

The Merkle root is computed and checked for existence in the contract using the verifyProofInclusion function of the AlignedProofAggregationService contract, which:

  1. Computes the merkle root
  2. Returns true or false depending on whether there exists an aggregatedProof with the computed root.

Data Availability

When submitting the aggregated proof to Ethereum, we include a blob that contains the commitments of all the individual proofs that were aggregated. This blob serves two main purposes:

  • It makes the proof commitments publicly available for 18 days.
  • It allows users to:
    • Inspect which proofs were aggregated
    • Get a Merkle proof to verify that their proof is included in the aggregated proof