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Components

caution

We are building Aztec as transparently as we can. The documents published here are living documents. They are largely complete, but changing reguarly.

If you would like to help us build Aztec, consider reviewing our GitHub to contribute code and joining our forum to participate in discussions.

You can track the development of these components in the aztec3-packages repo.

KeyStore​

Responsibilities:

  • Holds and never exposes private keys.
  • Provides sign/decrypt functionality.

AztecRpcClient (Previously Wallet/Private Client)​

Responsibilities:

  • Shields any upstream entities (dapp) from private information.
  • Shields any downstream entities (Public Client) from private information.
  • Maintains an up-to-date view of required parts of the global state from state streams to generate a tx.
  • Maintains an up-to-date view of state for accounts in a KeyStore.

PublicClient​

Responsibilities:

  • Acts largely as a facade to sub-systems.
  • Provide methods for access Merkle Tree data (SiblingPathSource).
  • Provide methods for requesting storage slot data for public state.
  • Provide methods for requesting published rollup data (RollupSource).
  • Receives txs and broadcasts them to the network via the P2PClient.

P2PClient​

Responsibilities:

  • Receives txs from the PublicClient.
  • Receives txs from other P2PClient instances in the network.
  • Verifies received txs meet criteria to be added to the pool.
  • Forwards all valid txs to other P2PClient instances in the network.
  • Receives rollups and purges settled or now invalid txs from local pool.
  • Purges txs that are older than a certain threshold from the local pool.

SiblingPathSource​

Responsibilities:

  • Returns the sibling path for the given tree_id at the given leaf index.
  • Can be injected into any context that requires path queries for a particular tree. Might be backed by implementations that call out to a server (where privacy doesn't matter, or during early development), or leverages some privacy tech (query via Nym), or could just point to a local WorldStateSynchroniser.

RollupSource​

Responsibilities:

  • Can be queried for Rollup data.

RollupReceiver​

Responsibilities:

  • Given the necessary rollup data, verifies it, and updates the underlying state accordingly to advance the state of the system.

TxReceiver​

Responsibilities:

  • Receives a tx, performs necessary validation, and makes it available to SequencerClient instances for rolling up.

TxPool​

Responsibilities:

  • Gives a view of the pending transaction pool.

Module Implementation Notes​

Noir​

These tasks are lower priority than providing a handcrafted ABI.

  • The ability for a dev to enclose a collection of Noir functions in a 'contract scope'.
  • The ability to create a Noir contract abi from the above.

Design a Noir Contract ABI, similar to a Solidity ABI which is output by Solc (see here). It might include for each function:

  • ACIR++ opcodes (akin to Solidity bytecode).
  • Function name and parameter names & types.
  • Public input/output witness indices?
  • Sourcemap information, allowing building of stack traces in simulator error cases.

aztec-cli​

Provides the aztec-cli binary for interacting with network from the command line. It's a thin wrapper around aztec.js to make calls out to the client services. It's stateless.

aztec.js​

Should provide sensible API, that provides the following functionalities. Start by writing the single e2e test that will check for the successful contract deployment. We don't need to get this perfect, but think hard about making the process feel very natural to a user of the library.

aztec.js should always be stateless. It offers the ability to interact with stateful systems such as the public and private clients.

The analogous AC component would be the AztecSdk (wraps the CoreSdk which is more analogous to the private client).

  • Allows a user to create an Aztec keypair. Call create_account on Wallet.
  • Create a Contract instance (similar to web3.js), given a path to a Noir Contract ABI.
  • Construct tx_request by calling e.g. contract.get_deployment_request(constructor_args).
  • Call wallet sign_tx_request(tx_request) to get signature.
  • Call simulate_tx(signed_tx_request) on the Private Client. In future this would help compute gas, for now we won't actually return gas (it's hard). Returns success or failure, so client knows if it should proceed, and computed kernel circuit public outputs.
  • Call create_tx(signed_tx_request) on Private Client to produce kernel proof. Can be skipped for this milestone. In future should be able to generate either mock (few constraints) or real proof.
  • Call send_tx(tx) on Private Client to send kernel proof to Public Client. Get back a receipt.
  • Wait until the receipt is settled with repeated calls to get_tx_receipt on the Private Client.

ethereum.js​

L1 client library. No ethers.js. Uses our existing and new L1 client code.

TestKeyStore​

Interfaces Implemented:

  • KeyStore

Implementation notes for this milestone:

  • Exposes a single account, created by a private key given in the ctor, that defaults to some test key.
  • Can be used as both the spending and decryption key for early development.

AztecRpcServer (Previously Wallet/Private Client)​

Implements:

  • AztecRpcClient (The server is a client, when used directly)

Injected:

  • KeyStore

Implementation notes for this milestone:

  • Avoid saving any state for now. Just resync from the PublicClient on startup.
  • Avoid needing to sync the merkle trees for now. Just use SiblingPathSource that queries the paths from the PublicClient.
  • simulate_tx
    • Can compute the contract's leaf (which will be inserted into the contract tree). See diagram linked at top of page.
    • Can spin-up a simulator instance for the constructor function.
      • (Note, executing an interesting constructor function is not until the next milestone, but we still need to execute a no-op constructor function for a contract deployment, since the public inputs of the constructor carry some contract deployment info, and need to passed into the kernel circuit).
    • Simulator will check whether the tx will succeed. It will return all public inputs/outputs.
    • Can collect/generate additional data required for kernel circuit execution.
    • Can pass the fake constructor proof, public inputs, and other kernel circuit data into a kernel simulator.
    • Returns if the simulation succeeded, and the public inputs/outputs of the kernel circuit.
  • create_tx
    • For this milestone, will just do the same as simulate_tx.
    • Returns a tx that can be sent to send_tx with everything but actual proof data.
  • send_tx
    • Forwards the given tx to the Public Client.

PublicClientImpl​

Implements:

  • PublicClient

Injected:

  • P2PClient
  • RollupSource
  • MerkleTreeDb

Implementation notes for this milestone:

  • Mostly acting as a facade for other components, forwards requests as necessary.
  • A WorldStateSynchroniser will ingest rollups from the RollupSource and maintain an up-to-date MerkleTreeDb.

MemoryP2PClient​

Implements:

  • P2PClient

Injected:

  • RollupSource
  • MerkleTreeDb

Implementation notes for this milestone:

  • For this milestone there won't be any p2p network.
  • Perform relevant validations possible in this milestone (e.g. check no tree conflicts, skip proof verification).
  • Purge relevant txs from pool on rollup receipt.
  • Store txs in an in memory map of txId -> tx.

Sequencer Client​

Responsibilities:

  • Wins a period of time to become the sequencer (depending on finalised protocol).
  • Chooses a set of txs from the tx pool to be in the rollup.
  • Simulate the rollup of txs.
  • Adds proof requests to the request pool (not for this milestone).
  • Receives results to those proofs from the network (repeats as necessary) (not for this milestone).
  • Publishes L1 tx(s) to the rollup contract via RollupPublisher.

For this milestone, the sequencer will just simulate and publish a 1x1 rollup and publish it to L1.

MerkleTreeDb​

Implements:

  • SiblingPathSource

Implementation notes for this milestone:

Closest analogous component in AC is the WorldStateDb in bb.js. We can configure the backing store (probably leveldb) to be an in-memory only store. We don't need persistence, we will rebuild the tree at startup. This will ensure we have appropriate sync-from-zero behaviour.

Responsibilities:

  • "Persists" the various merkle trees (configurable).
    • For this milestone 1.1, we'll need the following trees:
      • Contract Tree
      • Contract Tree Roots Tree (the tree whose leaves are the roots of historic rollups' contract trees)
      • Nullifier Tree (so that the contract address can never be re-registered in a future deployment)
        • Note: Suyash has implemented C++ for the 'new' kind of nullifier tree.
  • Provides methods for updating the trees with commit, rollback semantics.
  • Provides methods for getting hash paths to leafs in the trees.

Interface:

  • get_root
  • get_num_leaves
  • get_sibling_path
  • append_leaves

WorldStateSynchroniser​

Injected:

  • RollupSource
  • MerkleTreeDb

Responsibilities:

  • Receives new rollups from the RollupSource and updates trees in the MerkleTreeDb.

Rollup Archiver​

Implements:

  • RollupSource

Responsibilities:

  • Pulls data in from whatever sources are needed, to fully describe a rollup e.g.
    • L1 calldata (provessRollup and offchainData for this milestone.)
    • ETH blobs (not before they are released).
    • Other sources that have archived historical ETH blobs (not before they are released).
  • Combines these sources of data to describe a Rollup.
  • Can be queried for the rollup data.

Interface:

  • get_latest_rollup_id
  • get_rollups(from, take)

Rollup Publisher​

Implements:

  • RollupReceiver

Implementation notes for this milestone:

  • We can leverage most of the logic from Falafels old RollupPublisher.
  • On receipt of a rollup, will publish to L1 and respond with success or failure.

Rollup Smart Contract​

Interface:

  • processRollup(proofData, l1Data)
  • offchainData(data)

Implementation notes for this milestone:

The rollup contract in AC holds data in two places that are reconciled when processing the rollup. The calldata passed into the processRollup function, and the calldata passed into the offchainData function. They were separated, as only the data given to processRollup is needed to ensure rollup liveness (i.e. if the "offchain data" were not published, we could still produce rollups). Ultimately the plan was to move the offchain data off of L1 altogether to reduce costs.

For this milestone, we will want to leverage a similar separation of data. The data to processData will consist of:

  • proofData - The proof data to be fed to the verifier. Likely will have a public inputs that represent:
    • The hash of the data in the offchain data (should use whatever commitment scheme Eth Blobs will use).
    • Recursion point fields.
  • l1Data - Data that is needed for making L2 - L1 function calls.

For logic:

  • Can receive a rollup proof and verify it (verifier just returns true for this milestone).
  • Can update the state hash (which would only represent an update to the contract tree, at this milestone).

For offchainData:

  • Receives relevant calldata that needs to be broadcast. For contract deployment, this might be:
    • Acir opcodes.
    • Constructor arguments.
    • Contract address & contract leaf.

Kernel Circuit functionality​

  • Can validate the signature of a signed tx object.
  • Can verify a 'previous' mock kernel circuit (this code is already in there).
  • Can verify the constructor function's proof (this functionality is already in there).
  • Can check contract deployment logic. (Note: it won't contain checks for private circuit execution logic, as that's for a future milestone).

Rollup Circuit functionality​

  • TODO: more discussion needed to understand exactly what's needed here.
  • Can verify a kernel circuit proof
  • Can compute the contract's address
  • Can compute a 'nullifier' for the contract's address, to prevent it being used again (possibly defer this, because we don't want to care about a nullifier tree in this milestone).
  • Can compute the contract leaf for the contract (see diagrams).
  • Can insert the contract's leaf into the contract tree.
  • Can insert the contract tree's root into a "tree of contract tree roots".
  • ???? Verifies the ACIR Verification proof (see Contract Creation doc by Zac)

Glossary​

  • witness: Any value within the circuit, by default these are private, and thus not visible on the proof. Some witnesses may be made public (visible on the proof), at which point they also become public_inputs.
  • [circuit_]input: Data that is computed outside the circuit and is fed in at the beginning as a witness. Note: if the context of this relating to a 'circuit' is already clear, we can omit circuit_, as is done in the aztec3_circuits repo.
  • oracle_input: Data that, during execution, is fetched from the oracle, and made a witness.
  • computed_public_input: Data that is computed within the circuit, and set to be a public_input.
  • public_input: Data that is set to be public by the circuit. This could include some circuit_input data, and/or some computed_public_input data, and/or some oracle_input data.

Participate​

Keep up with the latest discussion and join the conversation in the Aztec forum.