Proof Aggregation Service

Proof Aggregation Service L2 integration example

This guide demonstrates how to build a dummy L2 application that integrates with Aligned's Proof Aggregation Service. The L2 does not post state diffs or any data to Ethereum, only commitments. The prover has to prove that:

1. The state database used in the proof must match the commitment stored in the on-chain contract. This is validated by computing the commitment of the received data in the zkvm and then exposing it as a public input.

2. The users performing the transfers have enough balance

After processing the transfers, the vm computes the commitment of the post state, which is exposed as a public input. The smart contract then updates the on-chain state root. If a user later wants to retrieve their state, the application must return it along with a Merkle proof, so they can verify it against the contract’s state root.

Notice a lot of checks that a real L2 should have are missing, since the focus are on the integration of Aligned.

The code can be viewed at examples/l2.

L2 workflow overview

This Layer 2 (L2) system operates in two main steps:

• Off-chain execution and proof generation + verification with Aligned's Proof Verification Layer.

• On-chain state update via proof verification with Aligned's Proof Aggregation Service.

In Step 1, we execute user transfers and generate a zkVM-based proof of the state transition, which is submitted to Aligned’s verification layer.

In Step 2, once the proof is aggregated (every 24 hours), it is verified on-chain to update the global state.

Step 1: Off-Chain Execution + Proof Generation

1. Initialize State: Load or initialize the current system state.

2. Load Transfers: Retrieve or receive the user transfer data for this batch.

3. Execute in zkVM: Run the zkVM with the loaded transfers to compute the new state.

4. Generate Proof: Produce a zk-proof for the executed state transition committing the commitment of the received + the commitment of the new state.

5. Submit Proof to Aligned: Send the proof to Aligned Verification Layer

6. Save the binary proof locally for later on-chain verification.

Step 2: Proof Verification + On-Chain State Update

1. Load the proof binary: Retrieve the saved proof binary from disk.

2. Update On-Chain State: Call the smart contract method updateStateTransition, which:

   • Internally calls verifyProofInclusion on AlignedProofAggregationService which:

     1. Computes the proof commitment from the proof public_inputs and program_id.

     2. Uses the Merkle proof to reconstruct and validate the Merkle root.

     3. Confirms whether there exists and aggregated proof with that root.

   • Validates that the initial_state_root proof public input matches the on-chain state.

   • If valid, updates the on-chain state root to the post_state_root.

Usage

Requirements

1. Rust: we have tested in v1.85.1

2. Foundry

3. Docker: for SP1 prover

Submodules of the repo should be imported by running on the root folder:

make submodules

You can run the example on:

• Holesky

• Localnet

Setup Holeksy

1. Create keystore

You can use cast to create a local keystore. If you already have one you can skip this step.

cast wallet new-mnemonic

Then you can import your created keystore using:

cast wallet import --interactive <path_to_keystore.json>

Then you need to obtain some funds to pay for gas and proof verification. You can do this by using this faucet

This same wallet is used to send the proof via aligned, so you'll also need to fund it on aligned. Follow this guide.

2. Deploy the contract

• Generate the base .env:

make gen_env_contract_holesky

• Get the program ID of the l2 program you are proving:

make generate_program_id

• Complete the following fields contracts/.env file:

  • PROGRAM_ID= (use the previously generated ID, you can re check with a cat ./crates/l2/programs_ids.json )

  • PRIVATE_KEY: the private key used for the deployment, it needs to have some funds to pay for the deployment.

  • OWNER_ADDRESS: you have to provide the address of the wallet created in step 1..

• Deploy the contracts with:

make deploy_contract

Save the output contract address.

3. Setup the L2

• Generate the base .env run:

make gen_env_l2_holesky

• Complete the missing fields on the .env:

  • PRIVATE_KEY_STORE_PATH: The path to the keystore created in 1..

  • PRIVATE_KEY_STORE_PASSWORD: The password of the keystore crated in step 1..

  • STATE_TRANSITION_CONTRACT_ADDRESS: The address of the contract deployed in step 2.

Finally run the l2.

Setup Localnet

You can also run this example on a local devnet. To get started, navigate to the root of the Aligned repository

• Start Ethereum package and the Batcher

# This will start the local net
make ethereum_package_start
# Start the batcher
make batcher_start_ethereum_package

• Navigate back to the example directory:

cd examples/l2

• Generate the .env files for the contracts and L2:

make gen_env_contract_devnet
make gen_env_l2_devnet

• Generate a pre funded wallet (or create one as specified previously here):

# This will generate the keystore and fund it on aligned
make gen_devnet_owner_wallet

• Generate the program ID of the program that is going to be proven:

make generate_program_id

• Set the generated program ID on contracts/.env.

• Deploy the contract

make deploy_contract

• Set the output address of the contract in .env

• run the l2

Running the L2

• Set up the initial State

make init_state

• Perform the L2 account updates and prove them in the zkvm:

make prove_state_transition

• Wait 24 hs for the proof to be aggregated, or if running locally, run the aggregator with either:

  ```make start_proof_aggregator_ethereum_package AGGREGATOR=sp1```

  or with cuda: make start_proof_aggregator_gpu_ethereum_package AGGREGATOR=sp1

• Update state transition on chain:

make update_state_on_chain

You should see a transaction receipt in the console and after the stateRoot updated on-chain.