Circom circuits for browser-side ZK proof generation in TSN shielded transactions.

These circuits mirror the Rust arkworks circuits exactly, enabling:

• Browser proving: Generate proofs client-side using snarkjs
• Server verification: Verify proofs on the Rust backend
• Cross-platform compatibility: Same constraints, same verification

Proves valid consumption of a note:

1. Note commitment was correctly computed
2. Note exists in the commitment tree (Merkle proof)
3. Nullifier was correctly derived

Proves valid creation of a note:

1. Note commitment was correctly computed

• Node.js >= 16
• circom >= 2.1.0
• snarkjs

npm install

npm run compile:all

Download powers of tau ceremony file:

wget https://hermez.s3-eu-west-1.amazonaws.com/powersOfTau28_hez_final_20.ptau

Generate circuit-specific keys:

npm run setup:spend
npm run setup:output

Contribute randomness (optional but recommended):

snarkjs zkey contribute build/spend_0000.zkey build/spend_final.zkey
snarkjs zkey contribute build/output_0000.zkey build/output_final.zkey

Export verification keys:

npm run export:spend-vkey
npm run export:output-vkey

These MUST match the Rust implementation:

• DOMAIN_NOTE_COMMITMENT = 1
• DOMAIN_VALUE_COMMITMENT_HASH = 2
• DOMAIN_NULLIFIER = 3
• DOMAIN_MERKLE_EMPTY = 4
• DOMAIN_MERKLE_NODE = 5

{
  "merkleRoot": "field_element_as_decimal_string",
  "nullifier": "field_element_as_decimal_string",
  "valueCommitmentHash": "field_element_as_decimal_string",
  "value": 1000,
  "recipientPkHash": "field_element_as_decimal_string",
  "noteRandomness": "field_element_as_decimal_string",
  "nullifierKey": "field_element_as_decimal_string",
  "pathElements": ["field_element", ...],  // 32 elements
  "pathIndices": [0, 1, 0, ...],           // 32 bits
  "position": 5
}

{
  "noteCommitment": "field_element_as_decimal_string",
  "valueCommitmentHash": "field_element_as_decimal_string",
  "value": 1000,
  "recipientPkHash": "field_element_as_decimal_string",
  "noteRandomness": "field_element_as_decimal_string"
}

After setup, distribute these files with your wallet:

• build/spend.wasm - Spend circuit WASM (~1-2MB)
• build/output.wasm - Output circuit WASM (~1-2MB)
• build/spend_final.zkey - Spend proving key (~50-100MB)
• build/output_final.zkey - Output proving key (~50-100MB)
• build/spend_vkey.json - Spend verification key (~1KB)
• build/output_vkey.json - Output verification key (~1KB)

import * as snarkjs from 'snarkjs';

async function generateSpendProof(witness) {
  const { proof, publicSignals } = await snarkjs.groth16.fullProve(
    witness,
    '/circuits/spend.wasm',
    '/circuits/spend_final.zkey'
  );
  return { proof, publicSignals };
}

npm test

• The trusted setup ceremony should involve multiple independent contributors
• Proving keys should be verified against the verification keys before use
• Circuit parameters must match the Rust backend exactly