darkfi/proofs/burn.zk

constant "Burn" {
	EcFixedPoint VALUE_COMMIT_VALUE,
	EcFixedPoint VALUE_COMMIT_RANDOM,
	EcFixedPoint NULLIFIER_K,
}

contract "Burn" {
	Base secret,
	Base serial,
	Base value,
	Base token,
	Base coin_blind,
	Scalar value_blind,
	Scalar token_blind,
	Uint32 leaf_pos,
	MerklePath path,
	Base signature_secret,
}

circuit "Burn" {
	# Poseidon hash of the nullifier
	nullifier = poseidon_hash(secret, serial);
	constrain_instance(nullifier);

	# Pedersen commitment for coin's value
	vcv = ec_mul_short(value, VALUE_COMMIT_VALUE);
	vcr = ec_mul(value_blind, VALUE_COMMIT_RANDOM);
	value_commit = ec_add(vcv, vcr);
	# Since value_commit is a curve point, we fetch its coordinates
	# and constrain them:
	value_commit_x = ec_get_x(value_commit);
	value_commit_y = ec_get_y(value_commit);
	constrain_instance(value_commit_x);
	constrain_instance(value_commit_y);

	# Pedersen commitment for coin's token ID
	tcv = ec_mul_short(token, VALUE_COMMIT_VALUE);
	tcr = ec_mul(token_blind, VALUE_COMMIT_RANDOM);
	token_commit = ec_add(tcv, tcr);
	# Since token_commit is also a curve point, we'll do the same
	# coordinate dance:
	token_commit_x = ec_get_x(token_commit);
	token_commit_y = ec_get_y(token_commit);
	constrain_instance(token_commit_x);
	constrain_instance(token_commit_y);

	# Coin hash
	pub = ec_mul_base(secret, NULLIFIER_K);
	pub_x = ec_get_x(pub);
	pub_y = ec_get_y(pub);
	C = poseidon_hash(pub_x, pub_y, value, token, serial, coin_blind);

	# Merkle root
	root = calculate_merkle_root(leaf_pos, path, C);
	constrain_instance(root);

	# Finally, we derive a public key for the signature and
	# constrain its coordinates:
	signature_public = ec_mul_base(signature_secret, NULLIFIER_K);
	signature_x = ec_get_x(signature_public);
	signature_y = ec_get_y(signature_public);
	constrain_instance(signature_x);
	constrain_instance(signature_y);

	# At this point we've enforced all of our public inputs.
}