darkfi/script/research/rln/signal.zk

constant "RlnSignal" {}

contract "RlnSignal" {
	Base secret_key,
	MerklePath identity_path,
	Uint32 identity_leaf_pos,

	# These are public so have to be properly constructed
	Base message_hash, # x
	Base epoch,
	Base rln_identifier,
}

circuit "RlnSignal" {
	constrain_instance(epoch);
	constrain_instance(rln_identifier);
	constrain_instance(message_hash);

	# This has to be the same constant used outside
	identity_derivation_path = witness_base(11);
	nullifier_derivation_path = witness_base(12);

	identity_commit = poseidon_hash(identity_derivation_path, secret_key);
	root = merkle_root(identity_leaf_pos, identity_path, identity_commit);
	constrain_instance(root);

	external_nullifier = poseidon_hash(epoch, rln_identifier);
	a_1 = poseidon_hash(secret_key, external_nullifier);
	internal_nullifier = poseidon_hash(nullifier_derivation_path, a_1);
	constrain_instance(internal_nullifier);

	y_a = base_mul(a_1, message_hash);
	y = base_add(y_a, secret_key);
	constrain_instance(y);
}