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voting example, detect bad vote

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Oskar Thoren 2019-11-02 16:00:11 +08:00
parent 1b5f398fc2
commit aaf9dd2b8b
No known key found for this signature in database
GPG Key ID: B2ECCFD3BC2EF77E
1 changed files with 96 additions and 14 deletions
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110
zksnarks/semaphore/src/hello.js
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@ -45,18 +45,18 @@ function generateIdentity() {
// XXX: Right now just using random bytes, what should this be?
const identity_nullifier = '0x' + crypto.randomBytes(31).toString('hex');
const identity_trapdoor = '0x' + crypto.randomBytes(31).toString('hex');
log(`generate identity from (private_key, public_key[0], public_key[1], identity_nullifier): (${private_key}, ${pubKey[0]}, ${pubKey[1]}, ${identity_nullifier}, ${identity_trapdoor})`);
//log(`generate identity from (private_key, public_key[0], public_key[1], identity_nullifier): (${private_key}, ${pubKey[0]}, ${pubKey[1]}, ${identity_nullifier}, ${identity_trapdoor})`);
const identity_commitment = pedersenHash([bigInt(circomlib.babyJub.mulPointEscalar(pubKey, 8)[0]), bigInt(identity_nullifier), bigInt(identity_trapdoor)]);
log(`identity_commitment: ${identity_commitment}`);
//log(`identity_commitment: ${identity_commitment}`);
const generated_identity = {
private_key,
identity_nullifier: identity_nullifier.toString(),
identity_trapdoor: identity_trapdoor.toString(),
identity_commitment: identity_commitment.toString()
};
console.log("Identity commitment (Save this to load identity)", identity_commitment.toString());
//console.log("Identity commitment (Save this to load identity)", identity_commitment.toString());
const filename = "build/identity_commitment_" + identity_commitment.toString();
// XXX: Maybe not needed here, weird BigInt parsing
fs.writeFileSync(filename, JSON.stringify(stringifyBigInts(generated_identity)), "utf8");
@ -101,7 +101,7 @@ function performSetup(circuit) {
fs.writeFileSync("myCircuit.vk_proof", JSON.stringify(stringifyBigInts(setup.vk_proof)), "utf8");
fs.writeFileSync("myCircuit.vk_verifier", JSON.stringify(stringifyBigInts(setup.vk_verifier)), "utf8");
console.log("Toxic waste:", setup.toxic); // Must be discarded.
//console.log("Toxic waste:", setup.toxic); // Must be discarded.
}
// Find path to a index containing identity commitment.
@ -121,16 +121,16 @@ function generateProofWithKey(witness) {
let proof = zkSnark.groth.genProof(unstringifyBigInts(vk_proof), unstringifyBigInts(witness));
const witness_hash = sha1(JSON.stringify(stringifyBigInts(witness)));
const filename = "build/witness_proof_" + witness_hash;
console.log("witness hash", filename);
//console.log("witness hash", filename);
fs.writeFileSync(filename, JSON.stringify(stringifyBigInts(proof)), "utf8");
console.log("proof done and persisted", proof);
//console.log("proof done and persisted", proof);
return proof;
}
function loadPreComputedProof(witness) {
const witness_hash = sha1(JSON.stringify(stringifyBigInts(witness)));
const filename = "build/witness_proof_" + witness_hash;
console.log("witness hash", filename);
//console.log("witness hash", filename);
log("loadPreComputedProof");
const proof = unstringifyBigInts(JSON.parse(fs.readFileSync(filename, "utf8")));
return proof;
@ -139,10 +139,10 @@ function loadPreComputedProof(witness) {
function loadOrGenerateProofWithKey(witness) {
let res;
try {
console.log("Looking for already existing proof...");
//log("Looking for already existing proof...");
res = loadPreComputedProof(witness);
} catch(err) {
console.log("Can't find proof for witness, generating new proof");
//log("Can't find proof for witness, generating new proof");
res = generateProofWithKey(witness);
}
return res;
@ -254,19 +254,19 @@ function run() {
// XXX: Not quite clear to me how this would work, since you have to verify with merkle tree
updateTreeAndGetPath(tree, 1, identity.identity_commitment)
.then((identity_path) => {
console.log("identity_path", identity_path);
//console.log("identity_path", identity_path);
// Input, what we want to signal
let signal_hash = signal("hello world");
console.log("signal hash", signal_hash);
//console.log("signal hash", signal_hash);
// In order to prevent double signals
// _How_ does it do this though?
// And how do we prove we are identity allowed to signal? What happens if identity isn't in tree?
let external_nullifier = bigInt(12312);
let msg = message(external_nullifier, signal_hash);
console.log("msg", msg);
//console.log("msg", msg);
let signature = sign(identity, msg);
console.log("signature", signature);
//console.log("signature", signature);
checkSignature(msg, signature, getPublicKey(identity));
let inputs = makeInputs(signature, signal_hash, external_nullifier, identity, identity_path);
let witness = circuit.calculateWitness(inputs);
@ -313,7 +313,7 @@ function badRun() {
verifyProofWithKey(proof, publicSignals);
}
run();
//run();
//badRun(); // XXX doesn't work right now
// nullifiers_hash is uniquely derived from external_nullifier, identity_nullifier and identity_path_index. This ensures a user cannot broadcast a signal with the same external_nullifier more than once.
@ -367,3 +367,85 @@ run();
// But it reveals a different 50% of the shares."
// Need to think about this more
// If this is a voting signal, how do we ensure voting only once? Fixed external nullifier
// In voting, we restrict external nullifier to a constant
// This way a given identity can only signal once
function votingExample(vote_token, vote_signal) {
let identity = loadIdentity("17939861921584559533262186509737425990469800861754459917147159747570381958900");
let tree = MakeMerkleTree();
let circuit = loadCircuit();
console.log("votingExample", vote_token, vote_signal);
// Add identity to tree
let res = updateTreeAndGetPath(tree, 1, identity.identity_commitment)
.then((identity_path) => {
//console.log("identity_path", identity_path);
// Input, what we want to signal
let signal_hash = signal(vote_signal);
//console.log("signal hash", signal_hash);
// Let's say external nullifier has to be this, if it isn't it should fail validation
let external_nullifier = vote_token;
let msg = message(external_nullifier, signal_hash);
//console.log("msg", msg);
let signature = sign(identity, msg);
//console.log("signature", signature);
checkSignature(msg, signature, getPublicKey(identity));
let inputs = makeInputs(signature, signal_hash, external_nullifier, identity, identity_path);
let witness = circuit.calculateWitness(inputs);
checkWitness(circuit, witness);
let {proof, publicSignals} = loadOrGenerateProofWithKey(witness);
return untrustedVerify(proof, publicSignals);
})
.catch((err) => {
console.log("error !", err);
return false;
});
return res;
}
function untrustedVerify(proof, publicSignals) {
let merkle_root = publicSignals[0];
let nullifier_hash = publicSignals[1];
let signal_hash = publicSignals[2];
let external_nullifier = publicSignals[3];
// This is the only valid external nullifier for this vote
// XXX: Is what we want to check nullifier hash?
// "With same external nullifier more than once"
let vote_token = BigInt(12312);
// TODO: Ensure part of merkle tree
// TODO: Signal again
try {
assert(external_nullifier == vote_token, "Wrong token!");
assert(verifyProofWithKey(proof, publicSignals));
console.log("All checks out!");
return true;
} catch(err) {
console.log("Assertions failed:", err.message);
return false;
};
}
async function voteTesting() {
try {
assert(await votingExample(BigInt(12312), "I vote for A") == true);
assert(await votingExample(BigInt(12319), "I vote for A") == false);
// TODO: voteState - keep track of nullifier hashes seen between runs
//assert(await votingExample(BigInt(12312), "I vote for B") == false);
// TODO: Bad identity, this requires constructing 'untrusted' tree and verifying
// root and nullifier hash (I believe)
} catch(err) {
console.log("Oops, no good", err);
}
};
voteTesting();