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Updated on April 27, 2021

Create and verify a Proof

Use gnark/backend

Once the circuit is compiled, you can run the three algorithms of a zk-SNARK back end:

  • Setup
  • Prove
  • Verify


Supported zk-SNARK backends are under gnark/backend. gnark currently implements Groth16 and an experimental version of PlonK.

Use a zk-SNARK back end

// 1. One time setup
pk, vk, err := groth16.Setup(cs)

// 2. Proof creation
proof, err := groth16.Prove(cs, pk, witness)

// 3. Proof verification
err := groth16.Verify(proof, vk, publicWitness)
// 1. One time setup
publicData, _ := plonk.Setup(cs, ...) // WIP

// 2. Proof creation
proof, err := plonk.Prove(r1cs, publicData, witness)

// 3. Proof verification
err := plonk.Verify(proof, publicData, publicWitness)

Construct the witness

Within a Go process, re-use the circuit data structure to construct the witness.

type Circuit struct {
    X frontend.Variable
    Y frontend.Variable `gnark:",public"`

var witness Circuit
// use the witness directly in zk-SNARK backend APIs
groth16.Prove(cs, pk, &witness)
// test file --> assert.ProverSucceeded(cs, &witness)


If witness is not built within the same process, or in another programming language, refer to Serialize.

Verify a Proof on Ethereum

On ecc.BN254 + Groth16, gnark can export the groth16.VerifyingKey as a solidity smart contract.

Refer to the code example and end-to-end integration test using a geth simulated blockchain.

// 1. Compile (Groth16 + BN254)
cs, err := frontend.Compile(ecc.BN254, backend.GROTH16, &myCircuit)

// 2. Setup
pk, vk, err := groth16.Setup(cs)

// 3. Write solidity smart contract into a file
err = vk.ExportSolidity(f)
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