Implement SolidityGenerator (#2)

* feat: implement `SolidityGenerator` to generate vk and verifier separately

* refactor: rename `generate` into `render`

* feat: implement `render` with test

* refactor: add `ConstraintSystemMeta` and `Data`

* refactor: better `Evaluator`

* refactor: fmt-able

* refactor: better `pcs`

* refactor: generally

* refactor: more `for_loop`

* refactor: docs

* refactor: cheaper than `snark-verifier`

* feat: add ci

* refactor: typo

* refactor: less generic

* refactor: `Word`

* feat: allow more instances and add document with example

* refactor: avoid patching `halo2_proofs`

* refactor: add more comments and reduce `encode_calldata` verbosity

* ci: install `svm-rs` with its `Cargo.lock`

* feat: handle `solc` related error in `compile_solidity` more properly

* docs: add warning on `README.md`

.github/workflows/ci.yml

@@ -0,0 +1,53 @@
+name: CI
+
+on:
+  pull_request:
+  push:
+    branches:
+      - main
+
+jobs:
+  test:
+    name: Test
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2
+
+      - name: Install toolchain
+        uses: actions-rs/toolchain@v1
+        with:
+          toolchain: stable
+          profile: minimal
+
+      - uses: Swatinem/rust-cache@v1
+        with:
+          cache-on-failure: true
+
+      - name: Install solc
+        run: (hash svm 2>/dev/null || cargo install --locked --git https://github.com/alloy-rs/svm-rs) && svm install 0.8.21 && solc --version
+
+      - name: Run test
+        run: cargo test --workspace --all-features --all-targets -- --nocapture
+
+  lint:
+    name: Lint
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2
+
+      - name: Install toolchain
+        uses: actions-rs/toolchain@v1
+        with:
+          toolchain: stable
+          profile: minimal
+          components: rustfmt, clippy
+
+      - uses: Swatinem/rust-cache@v1
+        with:
+          cache-on-failure: true
+
+      - name: Run fmt
+        run: cargo fmt --all -- --check
+
+      - name: Run clippy
+        run: cargo clippy --workspace --all-features --all-targets -- -D warnings

.gitignore

@@ -12,3 +12,6 @@ Cargo.lock
 
 # MSVC Windows builds of rustc generate these, which store debugging information
 *.pdb
+
+.vscode
+generated/

Cargo.toml

@@ -0,0 +1,31 @@
+[package]
+name = "halo2_solidity_verifier"
+version = "0.1.0"
+edition = "2021"
+
+[dependencies]
+halo2_proofs = { git = "https://github.com/privacy-scaling-explorations/halo2", tag = "v2023_04_20" }
+askama = { version = "0.12.0", features = ["config"], default-features = false }
+hex = "0.4.3"
+ruint = "1.10.1"
+sha3 = "0.10"
+itertools = "0.11.0"
+
+# Remove when `vk.transcript_repr()` is ready for usage.
+blake2b_simd = "1"
+
+# For feature = "evm"
+revm = { version = "3.3.0", optional = true }
+
+[dev-dependencies]
+rand = "0.8.5"
+revm = "3.3.0"
+halo2_maingate = { git = "https://github.com/privacy-scaling-explorations/halo2wrong", tag = "v2023_04_20", package = "maingate" }
+
+[features]
+default = []
+evm = ["dep:revm"]
+
+[[example]]
+name = "separately"
+required-features = ["evm"]

README.md

@@ -1,2 +1,46 @@
-# halo2_solidity_verifier
-A set of tooling related to halo2 circuits verification inside Solidity contracts
+# Halo2 Solidity Verifier
+
+> ⚠️ This repo has NOT been audited and is NOT intended for a production environment yet.
+
+Solidity verifier generator for [`halo2`](http://github.com/privacy-scaling-explorations/halo2) proof with KZG polynomial commitment scheme on BN254
+
+## Usage
+
+### Generate verifier and verifying key separately as 2 solidity contracts
+
+```rust
+let generator = SolidityGenerator::new(&params, &vk, Bdfg21, num_instances);
+let (verifier_solidity, vk_solidity) = generator.render_separately().unwrap();
+```
+
+Check [`examples/separately.rs`](./examples/separately.rs) for more details.
+
+### Generate verifier and verifying key in a single solidity contract
+
+```rust
+let generator = SolidityGenerator::new(&params, &vk, Bdfg21, num_instances);
+let verifier_solidity = generator.render().unwrap();
+```
+
+### Encode proof into calldata to invoke `verifyProof`
+
+```rust
+let calldata = encode_calldata(vk_address, &proof, &instances);
+```
+
+Note that function selector is already included.
+
+## Limitations
+
+- It only allows circuit with **exact 1 instance column** and **no rotated query to this instance column**.
+- Option `--via-ir` seems necessary when compiling the generated contract, otherwise it'd cause stack too deep error. However, `--via-ir` is not allowed to be used with `--standard-json`, not sure how to work around this yet.
+- Even the `configure` is same, the [selector compression](https://github.com/privacy-scaling-explorations/halo2/blob/7a2165617195d8baa422ca7b2b364cef02380390/halo2_proofs/src/plonk/circuit/compress_selectors.rs#L51) might lead to different configuration when selector assignments are different. To avoid this we might need to update halo2 to support disabling selector compression.
+- Now it only supports BDFG21 batch open scheme (aka SHPLONK), GWC19 is not yet implemented.
+
+## Compatibility
+
+The [`Keccak256Transcript`](./src/transcript.rs#L19) behaves exactly same as the `EvmTranscript` in `snark-verifier`.
+
+## Acknowledgement
+
+The template is heavily inspired by Aztec's [`BaseUltraVerifier.sol`](https://github.com/AztecProtocol/barretenberg/blob/4c456a2b196282160fd69bead6a1cea85289af37/sol/src/ultra/BaseUltraVerifier.sol).

askama.toml

@@ -0,0 +1,3 @@
+[[escaper]]
+path = "askama::Text"
+extensions = ["sol"]

examples/separately.rs

@@ -0,0 +1,242 @@
+use application::StandardPlonk;
+use prelude::*;
+
+use halo2_solidity_verifier::{
+    compile_solidity, encode_calldata, BatchOpenScheme::Bdfg21, Evm, Keccak256Transcript,
+    SolidityGenerator,
+};
+
+const K_RANGE: Range<u32> = 10..17;
+
+fn main() {
+    let mut rng = seeded_std_rng();
+
+    let params = setup(K_RANGE, &mut rng);
+
+    let vk = keygen_vk(&params[&K_RANGE.start], &StandardPlonk::default()).unwrap();
+    let generator = SolidityGenerator::new(&params[&K_RANGE.start], &vk, Bdfg21, 0);
+    let (verifier_solidity, _) = generator.render_separately().unwrap();
+    save_solidity("Halo2Verifier.sol", &verifier_solidity);
+
+    let verifier_creation_code = compile_solidity(&verifier_solidity);
+    let verifier_creation_code_size = verifier_creation_code.len();
+    println!("Verifier creation code size: {verifier_creation_code_size}");
+
+    let mut evm = Evm::default();
+    let verifier_address = evm.create(verifier_creation_code);
+
+    let deployed_verifier_solidity = verifier_solidity;
+
+    for k in K_RANGE {
+        let num_instances = k as usize;
+        let circuit = StandardPlonk::rand(num_instances, &mut rng);
+
+        let vk = keygen_vk(&params[&k], &circuit).unwrap();
+        let pk = keygen_pk(&params[&k], vk, &circuit).unwrap();
+        let generator = SolidityGenerator::new(&params[&k], pk.get_vk(), Bdfg21, num_instances);
+        let (verifier_solidity, vk_solidity) = generator.render_separately().unwrap();
+        save_solidity(format!("Halo2VerifyingKey-{k}.sol"), &vk_solidity);
+
+        assert_eq!(deployed_verifier_solidity, verifier_solidity);
+
+        let vk_creation_code = compile_solidity(&vk_solidity);
+        let vk_address = evm.create(vk_creation_code);
+
+        let calldata = {
+            let instances = circuit.instances();
+            let proof = create_proof_checked(&params[&k], &pk, circuit, &instances, &mut rng);
+            encode_calldata(vk_address.0.into(), &proof, &instances)
+        };
+        let (gas_cost, output) = evm.call(verifier_address, calldata);
+        assert_eq!(output, [vec![0; 31], vec![1]].concat());
+        println!("Gas cost of verifying standard Plonk with 2^{k} rows: {gas_cost}");
+    }
+}
+
+fn save_solidity(name: impl AsRef<str>, solidity: &str) {
+    const DIR_GENERATED: &str = "./generated";
+
+    create_dir_all(DIR_GENERATED).unwrap();
+    File::create(format!("{DIR_GENERATED}/{}", name.as_ref()))
+        .unwrap()
+        .write_all(solidity.as_bytes())
+        .unwrap();
+}
+
+fn setup(k_range: Range<u32>, mut rng: impl RngCore) -> HashMap<u32, ParamsKZG<Bn256>> {
+    k_range
+        .clone()
+        .zip(k_range.map(|k| ParamsKZG::<Bn256>::setup(k, &mut rng)))
+        .collect()
+}
+
+fn create_proof_checked(
+    params: &ParamsKZG<Bn256>,
+    pk: &ProvingKey<G1Affine>,
+    circuit: impl Circuit<Fr>,
+    instances: &[Fr],
+    mut rng: impl RngCore,
+) -> Vec<u8> {
+    use halo2_proofs::{
+        poly::kzg::{
+            multiopen::{ProverSHPLONK, VerifierSHPLONK},
+            strategy::SingleStrategy,
+        },
+        transcript::TranscriptWriterBuffer,
+    };
+
+    let proof = {
+        let mut transcript = Keccak256Transcript::new(Vec::new());
+        create_proof::<_, ProverSHPLONK<_>, _, _, _, _>(
+            params,
+            pk,
+            &[circuit],
+            &[&[instances]],
+            &mut rng,
+            &mut transcript,
+        )
+        .unwrap();
+        transcript.finalize()
+    };
+
+    let result = {
+        let mut transcript = Keccak256Transcript::new(proof.as_slice());
+        verify_proof::<_, VerifierSHPLONK<_>, _, _, SingleStrategy<_>>(
+            params,
+            pk.get_vk(),
+            SingleStrategy::new(params),
+            &[&[instances]],
+            &mut transcript,
+        )
+    };
+    assert!(result.is_ok());
+
+    proof
+}
+
+mod application {
+    use crate::prelude::*;
+
+    #[derive(Clone)]
+    pub struct StandardPlonkConfig {
+        selectors: [Column<Fixed>; 5],
+        wires: [Column<Advice>; 3],
+    }
+
+    impl StandardPlonkConfig {
+        fn configure(meta: &mut ConstraintSystem<impl PrimeField>) -> Self {
+            let [w_l, w_r, w_o] = [(); 3].map(|_| meta.advice_column());
+            let [q_l, q_r, q_o, q_m, q_c] = [(); 5].map(|_| meta.fixed_column());
+            let pi = meta.instance_column();
+            [w_l, w_r, w_o].map(|column| meta.enable_equality(column));
+            meta.create_gate(
+                "q_l·w_l + q_r·w_r + q_o·w_o + q_m·w_l·w_r + q_c + pi = 0",
+                |meta| {
+                    let [w_l, w_r, w_o] =
+                        [w_l, w_r, w_o].map(|column| meta.query_advice(column, Rotation::cur()));
+                    let [q_l, q_r, q_o, q_m, q_c] = [q_l, q_r, q_o, q_m, q_c]
+                        .map(|column| meta.query_fixed(column, Rotation::cur()));
+                    let pi = meta.query_instance(pi, Rotation::cur());
+                    Some(
+                        q_l * w_l.clone()
+                            + q_r * w_r.clone()
+                            + q_o * w_o
+                            + q_m * w_l * w_r
+                            + q_c
+                            + pi,
+                    )
+                },
+            );
+            StandardPlonkConfig {
+                selectors: [q_l, q_r, q_o, q_m, q_c],
+                wires: [w_l, w_r, w_o],
+            }
+        }
+    }
+
+    #[derive(Clone, Debug, Default)]
+    pub struct StandardPlonk<F>(Vec<F>);
+
+    impl<F: PrimeField> StandardPlonk<F> {
+        pub fn rand<R: RngCore>(num_instances: usize, mut rng: R) -> Self {
+            Self((0..num_instances).map(|_| F::random(&mut rng)).collect())
+        }
+
+        pub fn instances(&self) -> Vec<F> {
+            self.0.clone()
+        }
+    }
+
+    impl<F: PrimeField> Circuit<F> for StandardPlonk<F> {
+        type Config = StandardPlonkConfig;
+        type FloorPlanner = SimpleFloorPlanner;
+
+        fn without_witnesses(&self) -> Self {
+            unimplemented!()
+        }
+
+        fn configure(meta: &mut ConstraintSystem<F>) -> Self::Config {
+            meta.set_minimum_degree(4);
+            StandardPlonkConfig::configure(meta)
+        }
+
+        fn synthesize(
+            &self,
+            config: Self::Config,
+            mut layouter: impl Layouter<F>,
+        ) -> Result<(), Error> {
+            let [q_l, q_r, q_o, q_m, q_c] = config.selectors;
+            let [w_l, w_r, w_o] = config.wires;
+            layouter.assign_region(
+                || "",
+                |mut region| {
+                    for (offset, instance) in self.0.iter().enumerate() {
+                        region.assign_advice(|| "", w_l, offset, || Value::known(*instance))?;
+                        region.assign_fixed(|| "", q_l, offset, || Value::known(-F::ONE))?;
+                    }
+                    let offset = self.0.len();
+                    let a = region.assign_advice(|| "", w_l, offset, || Value::known(F::ONE))?;
+                    a.copy_advice(|| "", &mut region, w_r, offset)?;
+                    a.copy_advice(|| "", &mut region, w_o, offset)?;
+                    let offset = offset + 1;
+                    region.assign_advice(|| "", w_l, offset, || Value::known(-F::from(5)))?;
+                    for (column, idx) in [q_l, q_r, q_o, q_m, q_c].iter().zip(1..) {
+                        region.assign_fixed(
+                            || "",
+                            *column,
+                            offset,
+                            || Value::known(F::from(idx)),
+                        )?;
+                    }
+                    Ok(())
+                },
+            )
+        }
+    }
+}
+
+mod prelude {
+    pub use halo2_proofs::{
+        circuit::{Layouter, SimpleFloorPlanner, Value},
+        halo2curves::{
+            bn256::{Bn256, Fr, G1Affine},
+            ff::PrimeField,
+        },
+        plonk::*,
+        poly::{commitment::Params, kzg::commitment::ParamsKZG, Rotation},
+    };
+    pub use rand::{
+        rngs::{OsRng, StdRng},
+        RngCore, SeedableRng,
+    };
+    pub use std::{
+        collections::HashMap,
+        fs::{create_dir_all, File},
+        io::Write,
+        ops::Range,
+    };
+
+    pub fn seeded_std_rng() -> impl RngCore {
+        StdRng::seed_from_u64(OsRng.next_u64())
+    }
+}