tornado-trees/circuits/BatchTreeUpdate.circom
2021-02-02 15:23:09 +03:00

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include "../node_modules/circomlib/circuits/poseidon.circom";
include "../node_modules/circomlib/circuits/bitify.circom";
include "./MerkleTreeUpdater.circom";
include "./Utils.circom";
template TreeLayer(height) {
signal input ins[1 << (height + 1)];
signal output outs[1 << height];
component hash[1 << height];
for(var i = 0; i < (1 << height); i++) {
hash[i] = HashLeftRight();
hash[i].left <== ins[i * 2];
hash[i].right <== ins[i * 2 + 1];
hash[i].hash ==> outs[i];
}
}
// Inserts a leaf batch into a tree
// Checks that tree previously contained zero leaves in the same position
template BatchTreeUpdate(levels, batchLevels, zeroBatchLeaf) {
var height = levels - batchLevels;
var nLeaves = 1 << batchLevels;
signal input argsHash;
signal private input oldRoot;
signal private input newRoot;
signal private input pathIndices;
signal private input pathElements[height];
signal private input hashes[nLeaves];
signal private input instances[nLeaves];
signal private input blocks[nLeaves];
// Check that hash of arguments is correct
// We compress arguments into a single hash to considerably reduce gas usage on chain
component argsHasher = TreeUpdateArgsHasher(nLeaves);
argsHasher.oldRoot <== oldRoot;
argsHasher.newRoot <== newRoot;
argsHasher.pathIndices <== pathIndices;
for(var i = 0; i < nLeaves; i++) {
argsHasher.hashes[i] <== hashes[i];
argsHasher.instances[i] <== instances[i];
argsHasher.blocks[i] <== blocks[i];
}
argsHash === argsHasher.out;
// Compute hashes of all leaves
component leaves[nLeaves];
for(var i = 0; i < nLeaves; i++) {
leaves[i] = Poseidon(3);
leaves[i].inputs[0] <== instances[i];
leaves[i].inputs[1] <== hashes[i];
leaves[i].inputs[2] <== blocks[i];
}
// Compute batch subtree merkle root
component layers[batchLevels];
for(var level = batchLevels - 1; level >= 0; level--) {
layers[level] = TreeLayer(level);
for(var i = 0; i < (1 << (level + 1)); i++) {
layers[level].ins[i] <== level == batchLevels - 1 ? leaves[i].out : layers[level + 1].outs[i];
}
}
// Verify that batch subtree was inserted correctly
component treeUpdater = MerkleTreeUpdater(height, zeroBatchLeaf);
treeUpdater.oldRoot <== oldRoot;
treeUpdater.newRoot <== newRoot;
treeUpdater.leaf <== layers[0].outs[0];
treeUpdater.pathIndices <== pathIndices;
for(var i = 0; i < height; i++) {
treeUpdater.pathElements[i] <== pathElements[i];
}
}
// zeroLeaf = keccak256("tornado") % FIELD_SIZE
// zeroBatchLeaf is poseidon(zeroLeaf, zeroLeaf) (batchLevels - 1) times
component main = BatchTreeUpdate(20, 2, 21572503925325825116380792768937986743990254033176521064707045559165336555197)
// for mainnet use 20, 7, 17278668323652664881420209773995988768195998574629614593395162463145689805534
/*
zeros of n-th order:
21663839004416932945382355908790599225266501822907911457504978515578255421292
11850551329423159860688778991827824730037759162201783566284850822760196767874
21572503925325825116380792768937986743990254033176521064707045559165336555197
11224495635916644180335675565949106569141882748352237685396337327907709534945
2399242030534463392142674970266584742013168677609861039634639961298697064915
13182067204896548373877843501261957052850428877096289097123906067079378150834
7106632500398372645836762576259242192202230138343760620842346283595225511823
17278668323652664881420209773995988768195998574629614593395162463145689805534
209436188287252095316293336871467217491997565239632454977424802439169726471
6509061943359659796226067852175931816441223836265895622135845733346450111408
*/