fix: Circom Adapter (Groth16 over BLS12-381)

crates/provers/groth16/circom-adapter/Cargo.toml

@@ -11,5 +11,5 @@ repository.workspace = true
 lambdaworks-math.workspace = true
 lambdaworks-groth16.workspace = true
 
-serde = { version = "1.0" }
+serde = { version = "1.0", features = ["derive"] }
 serde_json = "1"

crates/provers/groth16/circom-adapter/README.md

@@ -0,0 +1,76 @@
+# Circom - Lambdaworks Groth16 Adapter
+
+This package allows one to perform trusted setup, prove, and verify constraints generated by [SnarkJS](https://github.com/iden3/snarkjs) from a [Circom](https://github.com/iden3/circom) circuit over [BLS12-381](https://github.com/lambdaclass/lambdaworks/tree/main/crates/math/src/elliptic_curve/short_weierstrass/curves/bls12_381).
+
+## Setup
+
+1. Install [Circom](https://github.com/iden3/circom) and [SnarkJS](https://github.com/iden3/snarkjs).
+
+2. Compile your circuit with `circom`, e.g. for a circuit named `test.circom` you would do:
+
+```bash
+circom test.circom --r1cs --wasm -p bls12381
+```
+
+> [!IMPORTANT]
+> Note that `-p bls12381` is important as that is the field supported by Lambdaworks Circom Adapter.
+
+3. Compiling a circuit like above will create a `test_js` directory, and a `test.r1cs` file. Now, we will create a witness for an input that is saved within `input.json`:
+
+```bash
+node test_js/generate_witness.js test_js/test.wasm input.json witness.wtns
+```
+
+This will generate a **witness.wtns** file.
+
+4. For the Circom Adapter we need to export the witness and R1CS files as JSON:
+
+```bash
+snarkjs wtns export json witness.wtns witness.wtns.json
+snarkjs r1cs export json test.r1cs test.r1cs.json
+```
+
+To do these steps all at once, you can copy-paste the following snippet to your terminal in the same directory as your circuit, using your own circuit name instead of `test` here:
+
+```bash
+circom test.circom --r1cs --wasm -p bls12381;
+
+node test_js/generate_witness.js test_js/test.wasm input.json witness.wtns;
+
+snarkjs wtns export json witness.wtns;
+snarkjs r1cs export json test.r1cs test.r1cs.json;
+```
+
+## Usage
+
+This crate exposes a `circom_to_lambda` function along with readers for R1CS and witness files. `circom_to_lambda` accepts a Witness and R1CS.
+
+```rust
+let circom_r1cs = read_circom_r1cs("test.r1cs.json").expect("could not read r1cs");
+let circom_wtns = read_circom_witness("witness.json").expect("could not read witness");
+
+let (qap, wtns, pubs) = circom_to_lambda(circom_r1cs, circom_wtns);
+```
+
+This function returns a Lambdaworks-compatible QAP, the witness assignments and public signals. Then one should perform setup, prove, and verify. Here's the complete procedure:
+
+```rust
+fn poseidon_parse_prove_verify() {
+    let (qap, wtns, pubs) = circom_to_lambda(
+      &fs::read_to_string("test.r1cs.json").expect("Error reading file"),
+      &fs::read_to_string("witness.json").expect("Error reading file"),
+    );
+
+    let (pk, vk) = setup(&qap);
+    let proof = Prover::prove(&wtns, &qap, &pk);
+    let accept = verify(&vk, &proof, &pubs);
+    assert!(accept);
+}
+```
+
+## Examples
+
+There are a few examples within the [tests](./tests/) folder:
+
+- [`poseidon_test.rs`](./tests/poseidon_test.rs): Poseidon hash of $100$ is proven and verified.
+- [`vitalik_test.rs`](./tests/vitalik_test.rs): Here we demonstrate the example from [Vitalik's Medium post](https://medium.com/@VitalikButerin/quadratic-arithmetic-programs-from-zero-to-hero-f6d558cea649) where $x^3 + x + 5 = 35$ is zk-proven.