README.md

🦀 semaphore-rs

Rust support library for using semaphore. It's mostly a Rust rewrite of zk-kit, but just focuses on semaphore (for now) and still covers a much smaller scope. It's using ark-circom under the hood for generating the groth16 proofs.

Usage

Add this line to your cargo.toml:

semaphore = { git = "https://github.com/worldcoin/semaphore-rs" }

Building semaphore circuits

1. Check out submodule (if not done before already): git submodule update --init --recursive
2. Install semaphore dependencies cd semaphore && npm install
3. Compile circuits npm exec ts-node ./scripts/compile-circuits.ts
4. You'll find the zkey and wasm file in semaphore/build/snark

Example

Example as in src/lib.rs, run with cargo test.

use semaphore::{get_supported_depths, hash_to_field, Field, identity::Identity,
                poseidon_tree::LazyPoseidonTree, protocol::*};
use num_bigint::BigInt;

// generate identity
let mut secret = *b"secret";
let id = Identity::from_secret(&mut secret, None);

// Get the first available tree depth. This is controlled by the crate features.
let depth = get_supported_depths()[0];

// generate merkle tree
let leaf = Field::from(0);
let mut tree = LazyPoseidonTree::new(depth, leaf).derived();
tree = tree.update(0, &id.commitment());

let merkle_proof = tree.proof(0);
let root = tree.root();

// change signal and external_nullifier here
let signal_hash = hash_to_field(b"xxx");
let external_nullifier_hash = hash_to_field(b"appId");

let nullifier_hash = generate_nullifier_hash(&id, external_nullifier_hash);

let proof = generate_proof(&id, &merkle_proof, external_nullifier_hash, signal_hash).unwrap();
let success = verify_proof(root, nullifier_hash, signal_hash, external_nullifier_hash, &proof, depth).unwrap();

assert!(success);