README.md

Circom example

The proof and verification key are generated following the Circom (circom compiler 2.2.2) getting-started guide.

The computation demonstrates a simple multiplication circuit: a * b = c, where:

• a and b are private inputs
• c is the public output

The contract implementation is auto-generated from verification_key.json using soroban-verifier-gen (Groth16 verifier generator for Soroban). The test suite demonstrates off-chain parsing of the proof and verification key, along with successful contract execution.

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Step-by-step Circom circuit setup and generation of keys/proof for the circom_verifier contract. Run the commands in order.

cd ./data/circom/auxiliary/

# Compile the circuit: R1CS, WASM build, and debug symbols; BLS12-381 curve (same as Soroban)
circom multiplier2.circom --r1cs --wasm --prime bls12381

# --- Trusted setup (Phase 1: Powers of Tau) ---
snarkjs powersoftau new bls12-381 5 pot5_0000.ptau -v
snarkjs powersoftau contribute pot5_0000.ptau pot5_0001.ptau --name="First contribution" -v -e="some random text"
snarkjs powersoftau prepare phase2 pot5_0001.ptau pot5_final.ptau -v

# Phase 2: circuit + ptau → initial zkey, then contribution
snarkjs groth16 setup Multiplier2.r1cs pot5_final.ptau Multiplier2_0000.zkey
snarkjs zkey contribute Multiplier2_0000.zkey Multiplier2_final.zkey --name="1st Contributor Name" -v -e="some random text"

# Export verification key (used by the contract)
snarkjs zkey export verificationkey Multiplier2_final.zkey ../verification_key.json

# Generate proof: inputs → proof + public signals (output in ../proof.json and ../public.json)
snarkjs groth16 fullprove input.json Multiplier2_js/Multiplier2.wasm Multiplier2_final.zkey ../proof.json ../public.json

cd ../../..

After running, data/circom/ will contain verification_key.json, proof.json, and public.json — use them to update the contract and tests.