Proving Coordination

Provers in the Aztec network coordinate with proposers through a request-for-quote (RFQ) process. This page explains how provers submit quotes and get selected to prove epochs.

Overview

Proposers run RFQs to obtain quotes from provers. Quotes are binding promises from provers to prove an entire epoch. The exact channel over which provers send quotes to proposers is NOT enshrined by the protocol.

However, Aztec Nodes will support two optional mechanisms that provers can use to submit quotes to proposers:

• Gossip quotes via the P2P
• Send a quote directly via HTTP (i.e. http://aztec-node:8000)

To send a quote via the P2P, do not set the environment variable PROVER_COORDINATION_NODE_URL and make sure that P2P_ENABLED is set to true.

For S&P Testnet: Please make sure that you are gossiping quotes via the P2P. Set P2P_ENABLED to true and do not use PROVER_COORDINATION_NODE_URL.

struct EpochProofQuote {
    Signature signature;
    address prover;
    uint256 epochNumber;
    uint256 epochInitBlock;
    uint256 epochFinalBlock;
    uint256 totalFees;
    address rollupAddress;
    uint32 basisPointFee;
    uint256 bondAmount;
}

To accomplish this coordination through the Aztec node software, we extend both the P2PClient and ProverNode.

P2P client

The P2PClient will be extended by:

class P2PClient {
    //...

    async addEpochProofQuote(quote: EpochProofQuote): Promise<void> {
        // Add quote to quote memory pool
        this.epochProofQuotePool.addQuote(quote);

        // Propagate quote via P2P
        this.broadcastEpochProofQuote(quote);
    }
}

This is called by the Prover Node inside ProverNode.sendEpochProofQuote() after it detects an epoch has ended.

Prover Node

As for the Prover Node, we add QuoteProvider and BondManager interfaces. Also an EpochMonitor which sits on the main start loop of the Prover Node. It fetches the most recent completed epochs and checks whether the proposer accepted an EpochProofQuote.

If no quote has been accepted yet, the EpochMonitor will call on BondManager and QuoteProvider to provide a valid quote. If the claim detected belongs to the prover, the monitor will kick off a handleCall() to create proving jobs.

interface BondManager {
  ensureBond(amount: number): Promise<void>;
}
interface QuoteProvider {
  getQuote(epoch: number): Promise<EpochProofQuote | undefined>;
}

When the prover node first starts up, it will call BondManager.ensureBond to ensure it has the minimum deposit amount PROVER_MINIMUM_ESCROW_AMOUNT deposited in the escrow contract. If it does not, it will top up to the target deposit amount PROVER_TARGET_ESCROW_AMOUNT.

Both PROVER_MINIMUM_ESCROW_AMOUNT and PROVER_TARGET_ESCROW_AMOUNT are customizable environment variables.

The EpochMonitor will then get the last completed, unproven epoch and will call the QuoteProvider to generate a quote if the epoch has not been claimed by any provers yet. The QuoteProvider will be provided with all the blocks in the unproven epoch so it could perform any custom logic to determine the quote parameters, i.e., bondAmount, basisPointFee, etc.

Alternatively, the quote provider can issue an HTTP POST to a configurable QUOTE_PROVIDER_URL to get the quote. The request body is JSON-encoded and contains the following fields:

• epochNumber: The epoch number to prove
• fromBlock: The first block number of the epoch to prove
• endBlock: The last block number (inclusive) of the epoch to prove
• txCount: The total number of txs in the epoch
• totalFees: The accumulated total fees across all txs in the epoch

The response is also expected in JSON and to contain basisPointFee and bondAmount fields. Optionally, the request can include a validUntilSlot parameter, which specifies for how many slots the quote remains valid. For example, an EpochProofQuote with parameters epochProofQuote#80 and validUntilSlot#5 means that any of the first 5 proposers in epoch 101 can “claim” this quote.

If no QUOTE_PROVIDER_URL is passed along to the Prover Node, then a SimpleQuoteProvider is used, which always returns the same basisPointFee and bondAmount as set in the QUOTE_PROVIDER_BASIS_POINT_FEE and QUOTE_PROVIDER_BOND_AMOUNT environment variables.

Quote Requirements

If the QuoteProvider does not return a bondAmount or a basisPointFee, the Prover Node will not generate nor submit a quote to the proposer.

Separately, the Prover Node needs a watcher on L1 to detect if its quote has been selected.

To this end, the L1Publisher will be extended with a new method to retrieve proof claims.

interface L1Publisher {
  getProofClaim(): Promise<EpochProofClaim>;
}

The Prover Node will call this method at least once per L2 slot to check for unclaimed accepted quotes if its quotes have been accepted. You can update the polling interval using the environment variable PROVER_NODE_POLLING_INTERVAL_MS.

Run a Prover

Go to the Prover Guide to run a prover.