1-multiplier

Installation

Install Rust and snarkjs.

Compilation

circom multiplier.circom --r1cs --wasm --sym

• --r1cs: it generates the file multiplier.r1cs that contains the R1CS constraint system of the circuit in binary format.
• --wasm: it generates the directory multiplier_js that contains the Wasm code (multiplier.wasm) and other files needed to generate the witness.
• --sym : it generates the file multiplier.sym, a symbols file required for debugging or for printing the constraint system in an annotated mode.

More options

Compute the Witness

• Add an input.json file which describes the values a and b
• run:

  node multiplier_js/generate_witness.js multiplier_js/multiplier.wasm input.json witness.wtns
  

Trusted Setup

Using Groth-16, Powers of Tau ceremony.

mkdir trusted_setup

Start the ceremony and contribute:

snarkjs powersoftau new bn128 12 trusted_setup/pot12_0000.ptau -v

snarkjs powersoftau contribute trusted_setup/pot12_0000.ptau trusted_setup/pot12_0001.ptau --name="First contribution" -v

Circuit-specific phase:

snarkjs powersoftau prepare phase2 trusted_setup/pot12_0001.ptau trusted_setup/pot12_final.ptau -v

snarkjs groth16 setup multiplier.r1cs trusted_setup/pot12_final.ptau trusted_setup/multiplier_0000.zkey

snarkjs zkey contribute trusted_setup/multiplier_0000.zkey trusted_setup/multiplier_0001.zkey --name="1st Contributor Name" -v

snarkjs zkey export verificationkey trusted_setup/multiplier_0001.zkey trusted_setup/verification_key.json

This phase creates both the prover key and verifier key.

Gebnerating a Proof

mkdir proof

snarkjs groth16 prove trusted_setup/multiplier_0001.zkey witness.wtns proof/proof.json proof/public.json

Verifying Locally

snarkjs groth16 verify trusted_setup/verification_key.json proof/public.json proof/proof.json

Verifying in a Smart Contract

Generate Verifier.sol

snarkjs zkey export solidityverifier trusted_setup/multiplier_0001.zkey multiplier_verifier.sol

Paste this into Remix.

Generate the Call

cd proof
snarkjs generatecall