tornado-core/circuits/withdraw.circom
2019-08-02 12:24:50 +03:00

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include "../node_modules/circomlib/circuits/bitify.circom";
include "../node_modules/circomlib/circuits/pedersen.circom";
include "merkleTree.circom";
// computes Pedersen(nullifier + secret)
template CommitmentHasher() {
signal private input nullifier;
signal private input secret;
signal output commitment;
signal output nullifierHash;
component commitmentHasher = Pedersen(496);
component nullifierHasher = Pedersen(248);
component nullifierBits = Num2Bits(248);
component secretBits = Num2Bits(248);
nullifierBits.in <== nullifier;
secretBits.in <== secret;
for (var i = 0; i < 248; i++) {
nullifierHasher.in[i] <== nullifierBits.out[i];
commitmentHasher.in[i] <== nullifierBits.out[i];
commitmentHasher.in[i + 248] <== secretBits.out[i];
}
commitment <== commitmentHasher.out[0];
nullifierHash <== nullifierHasher.out[0];
}
// Verifies that commitment that corresponds to given secret and nullifier is included in the merkle tree of deposits
template Withdraw(levels, rounds) {
signal input root;
signal input nullifierHash;
signal input receiver; // not taking part in any computations
signal input fee; // not taking part in any computations
signal private input nullifier;
signal private input secret;
signal private input pathElements[levels];
signal private input pathIndex[levels];
component hasher = CommitmentHasher();
hasher.nullifier <== nullifier;
hasher.secret <== secret;
nullifierHash === hasher.nullifierHash;
component tree = MerkleTree(levels, rounds);
tree.leaf <== hasher.commitment;
tree.root <== root;
for (var i = 0; i < levels; i++) {
tree.pathElements[i] <== pathElements[i];
tree.pathIndex[i] <== pathIndex[i];
}
// Add hidden signals to make sure that tampering with receiver or fee will invalidate the snark proof
// Most likely it is not required, but it's better to stay on the safe side and it only takes 2 constraints
// Squares are used to prevent optimizer from removing those constraints
signal receiverSquare;
signal feeSquare;
receiverSquare <== receiver * receiver;
feeSquare <== fee * fee;
}
component main = Withdraw(16, 220);