zkzkHeliosDocs

Build a custom circuit

Bring your own circom circuit and verify its proofs through the zkHelios program.

1. Write the circuit

circom
pragma circom 2.1.6;

template Membership(depth) {
  signal input leaf;
  signal input path[depth];
  signal input root;     // public
  signal output ok;
  // ... Merkle inclusion constraints ...
}
component main { public [root] } = Membership(20);

2. Compile + trusted setup

bash
circom membership.circom --r1cs --wasm
snarkjs groth16 setup membership.r1cs pot.ptau membership_0.zkey
snarkjs zkey contribute membership_0.zkey membership_final.zkey
snarkjs zkey export verificationkey membership_final.zkey vkey.json

3. Register the circuit on-chain

An admin registers the verifying key so the program can verify proofs for it:

ts
await zk.admin.registerCircuit({
  name: "membership_v1",
  proofType: "membership",
  verifyingKey: vkeyToBytes(vkey),
  publicInputCount: 1,
});
The verifying key is consensus-critical. Only register keys from a circuit you have audited and whose trusted setup you trust.

4. Prove with it

ts
const proof = await zk.proveCustom({
  circuit: "membership_v1",
  inputs: { leaf, path, root },
});
await zk.submitProof(proof);
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