Merge pull request #53 from worldcoin/chore/docs

Chore/docs

README.md

@@ -1,85 +1,13 @@
 # World Chain Builder
 
-The WorldChain Builder is a custom block builder for the OP Stack that provides Priority Blockspace for Humans (PBH). PBH enables verified World ID users to execute transactions with top of block priority, enabling a more frictionless user experience. This mechanism is designed to ensure that ordinary users aren’t unfairly disadvantaged by automated systems and greatly mitigates the impact of negative impacts of MEV. PBH also enables future flexibility, allowing for a separate EIP-1559-style fee market mechanism for verified transactions.
-
-
-## PBH Transaction Envelope
-The builder introduces a new EIP-2718 RLP encoded transaction envelope including a [Pbh Payload](https://github.com/worldcoin/world-chain/blob/8d60a1e79dbb3be68db075d49b3d0a8a67e45b3e/world-chain-builder/src/pbh/payload.rs#L50), which contains a World ID proof, proving the transaction was created by a verified human.
-
-```rust
-
-```rust
-#[derive(Clone, Debug, PartialEq, Eq)]
-pub struct WorldChainPooledTransactionsElement {
-    pub inner: PooledTransactionsElement,
-    pub pbh_payload: Option<PbhPayload>,
-}
-
-/// The payload of a PBH transaction
-///
-/// Contains the semaphore proof and relevent metadata
-/// required to to verify the pbh transaction.
-#[derive(Clone, Debug, RlpEncodable, RlpDecodable, PartialEq, Eq, Default)]
-pub struct PbhPayload {
-    /// A string containing a prefix, the date marker, and the pbh nonce
-    pub external_nullifier: String,
-    /// A nullifier hash used to keep track of
-    /// previously used pbh transactions
-    pub nullifier_hash: Field,
-    /// The root of the merkle tree for which this proof
-    /// was generated
-    pub root: Field,
-    /// The actual semaphore proof verifying that the sender
-    /// is included in the set of orb verified users
-    pub proof: Proof,
-}
-
-```
-
-## PBH Payload
-
-### External Nullifier
-
-The **External Nullifier** is a structured identifier used to ensure the uniqueness and proper sequencing of PBH transactions. Its format is defined as:
-
-### Schema
-`vv-mmyyyy-nn`
-
-- **Version Prefix (vv)**: Represents the version of the nullifier.
-  - Validation: Must match the current version.
-
-- **Date (mmyyyy)**: Represents the month and year.
-  - Validation: Must match the current month and year.
-
-- **PBH Nonce (nn)**: A `u16` value used to rate-limit PBH transactions.
-  - Validation: 
-    - The PBH Nonce must be ≤ 30 by default.
-    - This nonce limits the number of PBH transactions each user can submit per month.
-    - It resets at the beginning of each month and increments monotonically from 0 to `num_pbh_txs`.
-    - Any nonce greater than `num_pbh_txs` will be invalidated and excluded from the transaction pool.
-
-### Nullifier Hash
-
-The **Nullifier Hash** ensures that each PBH transaction is unique at the time of validation.
-
-- **Validation**: 
-  - The nullifier hash must be unique during transaction validation to prevent duplicate transactions.
-
-
-### Root
-
-The **Root** represents the root of the Merkle tree for which the proof was generated.
-
-- **Validation**: 
-  - Must match the `latestRoot` stored in the `OpWorldId` contract on L2.
-
-- **Additional Considerations**: 
-  - If the root has not yet synchronized with L1, there may be a window where a valid proof is perceived as invalid.
-  - To avoid transaction validation errors, the root should be read from L2 and asserted to match the root on L1 before submitting the transaction.
+The World Chain Builder is a custom block builder for the OP Stack that provides Priority Blockspace for Humans (PBH). PBH enables verified World ID users to execute transactions with top of block priority, enabling a more frictionless user experience. This mechanism is designed to ensure that ordinary users aren’t unfairly disadvantaged by automated systems and greatly mitigates the impact of negative impacts of MEV. PBH also enables future flexibility, allowing for a separate EIP-1559-style fee market mechanism for verified transactions.
 
+![World Chain Builder Architecture](assets/pbh-op-stack.png)
 
+To learn more about how PBH works, check out the docs detailing [the PBH Transaction Lifecycle](world-chain-builder/docs/pbh_tx_lifecycle.md), [World's blog post covering World Chain's builder architecture](https://world.org/blog/engineering/introducing-pbh-priority-blockspace-for-humans), and [the PBH architecture](world-chain-builder/docs/pbh_architecture.md).
 
 
+<!-- ## Installing -->
 
 ## Running the Devnet
 To spin up a OP Stack devnet with `rollup-boost` and the `world-chain-builder` deployed, make sure that you have [just](https://github.com/casey/just?tab=readme-ov-file) installed, and docker daemon running. Then simply run the following command.

devnet/Dockerfile.rollup-boost

@@ -1,5 +1,5 @@
 # Use the official Rust image for building
-FROM rust:1.81 AS builder
+FROM rust:1.82 AS builder
 
 # Set the working directory inside the container
 WORKDIR /app

world-chain-builder/docs/pbh_architecture.md

@@ -0,0 +1,20 @@
+### Network 
+World Chain is a [Optimistic Rollup](https://ethereum.org/en/developers/docs/scaling/optimistic-rollups/) on Ethereum. World Chain functions at the Consensus layer identically to that of Optimism, and other optimistic rollups. But differs at the execution layer in a couple ways. 
+
+In a traditional Optimistic Rollup the _Sequencer_ acts as the sole participant that proposes new blocks. 
+
+On World Chain we have two possible block proposers:
+
+1. `world-chain-builder` - Custom Ordering Policy
+2. _sequencer_ - An `op-geth` client constructing blocks with a canonical ordering policy. 
+
+The `world-chain-builder` is the favored proposer in the network. Meaning if the builder produces a valid block the builders block will always be accepted by the network over the sequencers block. 
+
+The sequencer has two jobs:
+
+1. Attest to the integrity of the Block Proposed by the Builder.
+2. Fallback such that if the builder produces an invalid payload, times out, or otherwise - The chain still moves forward.
+
+Two proposers on the network sequencing blocks is made possible by utilizing an [engine api](https://github.com/ethereum/execution-apis/blob/main/src/engine/common.md) proxy server multiplexing engine api calls from the consensus layer to both the _sequencer_, and the builder in parallel. We currently use [rollup-boost](https://github.com/flashbots/rollup-boost/tree/main) for this purpose.
+
+For a deep dive into rollup-boost checkout the [design spec](https://github.com/ethereum-optimism/design-docs/blob/main/protocol/external-block-production.md).

world-chain-builder/docs/pbh_tx_lifecycle.md

@@ -0,0 +1,60 @@
+# Lifecycle of a PBH Transaction
+
+The World Chain Builder is a custom block builder for the OP Stack that provides Priority Blockspace for Humans (PBH). PBH enables verified World ID users to execute transactions with top of block priority, enabling a more frictionless user experience. This mechanism is designed to ensure that ordinary users aren’t unfairly disadvantaged by automated systems and greatly mitigates the impact of negative impacts of MEV. PBH also enables future flexibility, allowing for a separate EIP-1559-style fee market mechanism for verified transactions.
+
+The builder introduces a new [EIP-2718 RLP encoded transaction envelope](https://eips.ethereum.org/EIPS/eip-2718) including the necessary data to verify the transaction was created by a valid World ID user. To get a deeper understanding of PBH, lets walk through the life cycle of a transaction. 
+
+
+## Creating a PBH transaction
+
+The contents of the PBH tx envelope simply consists of an [Ethereum typed transaction ](https://eips.ethereum.org/EIPS/eip-2718) and optional semaphore proof ensuring that the sender is verified World ID user. In order to create a PBH transaction envelope, first generate an [Ethereum transaction](https://ethereum.org/en/developers/docs/transactions/).
+
+Next, [create a World ID proof](), **setting the `signal` to the transaction hash of the tx you are verifying**, and set the `externalNullifier` to the following schema `vv-mmyyyy-nn` where:
+
+- **Version Prefix (vv)**: Indicates the version of the external nullifier schema This should be set to `0`.
+- **Date (mmyyyy)**: Indicates the current month and year.
+- **PBH Nonce (nn)**: A `u16` value used to rate-limit PBH transactions. 
+
+Upon receiving the PBH transaction envelope, the World Chain Builder first validates the inner Ethereum transaction and then verifies the PBH payload. The builder enforces a transaction limit for each verified user that resets every month (eg. 50 txs per month), tracked by the PBH nonce specified in the `externalNullifier`. The user creating the PBH envelope must track which nonces they have used, however nonces can be specified in any order. For example, a user could send a PBH tx envelope with a PBH nonce of `16`, followed by a PBH nonce of `10` and so on. Additional transaction validation will be covered further in a later section. 
+
+Below is a quick look at the `PbhTxEnvelope` in its entirety.
+
+```
+PbhTxEnvelope = { Tx, PbhPayload }
+PbhPayload = { externalNullifier, nullifierHash, root, proof }
+```
+- `Tx`: Any valid Ethereum typed transaction.
+- `externalNullifier`: String identifier used to ensure the uniqueness and proper sequencing of PBH transactions formatted as: `vv-mmyyyy-nn`.
+
+- `nullifierHash`: Hash of the identity nullifier and the external nullifier; used to prevent double-signaling. You can read more [about the nullifier and external nullifier here](https://docs.world.org/world-id/further-reading/protocol-internals#external-nullifier).
+
+- `root`: Root of the [Merkle tree representing the identity set](https://docs.world.org/world-id/further-reading/protocol-internals#signup-sequencer). This is the root used when creating the inclusion proof necessary to create a semaphore ZK proof.
+
+- `proof`: The semaphore proof verifying that the sender is a member of the identity set.
+
+
+## Sending the transaction to the Builder
+
+Since the PBH tx envelope is a valid [EIP-2718 Typed Transaction Envelope](https://eips.ethereum.org/EIPS/eip-2718), it can be sent to the builder via the `eth_sendRawTransaction` endpoint, just like any other node that implements the Engine API. 
+
+```bash
+curl -X POST \
+     -H "Content-Type: application/json" \
+     -d "{\"jsonrpc\":\"2.0\",\"method\":\"eth_sendRawTransaction\",\"params\":[\"$PBH_TX_BYTES\"],\"id\":480}" \
+     $BUILDER_ENDPOINT
+```
+
+
+
+## Transaction Validation
+// NOTE: PBH transactions are not gossiped or forwarded to the sequencer. All normal transactions are forwarded though
+
+
+## Transaction Priority and Block Production
+
+The `world-chain-builder` implements a custom [WorldChainEthApi](https://github.com/worldcoin/world-chain/blob/c44417727fcf510597aaf247dc1e2d8dca03a3b7/world-chain-builder/src/rpc/mod.rs#L52) that allows it to recieve PBH transaction envelopes over RPC through an `eth_sendRawTransaction` request. If a semaphore proof is attached to the transaction the [WorldChainTransactionValidator](https://github.com/worldcoin/world-chain/blob/c44417727fcf510597aaf247dc1e2d8dca03a3b7/world-chain-builder/src/pool/validator.rs#L37) will first validate the integrity of the proof, and if valid insert the transaction into the transaction pool with an associated bool indicating the pooled transaction is human verified. 
+
+The transaction pool implements a custom [ordering policy](https://github.com/worldcoin/world-chain/blob/c44417727fcf510597aaf247dc1e2d8dca03a3b7/world-chain-builder/src/pool/ordering.rs#L10) which guarantees top of block priority for verified human transactions. 
+
+A percentage of the block space is reserved for pbh transactions as defined by `verified_blockspace_capacity`. This value represents the maximum percentage of the block gas limit that will be dedicated to human verified transactions. If the amount of pbh transactions does not meet the threshold of reserved block space then non-verified transactions will fill this reserved block space. `100 - verified_blockspace_capacity` is the percentage of the block space always dedicated to non-verified transactions.
+