# Privacy Mixer

## <mark style="color:purple;">Privacy Mixer</mark>

Multi-layer privacy protocol using shielded pools, stealth addresses, and confidential transactions. Monero-level privacy for Ethereum.

### <mark style="color:purple;">Architecture</mark>

#### Shielded Pool System

Macro uses a continuous shielded balance system, not traditional deposit/withdraw mixing.

**How it works:**

* Assets move into encrypted on-chain balances (shielded pool)
* All transfers within pool are confidential (hidden amounts, addresses, transactions)
* Withdrawals use stealth addresses via decentralized relayers
* No public transaction graph

**Key components:**

**Note-based system** - Each balance is an encrypted note with hidden amount and owner

**Merkle tree** - All notes stored in on-chain Merkle tree

**Nullifiers** - Spent notes marked to prevent double-spending

**ZK-SNARKs** - Prove valid transactions without revealing details

#### Confidential Transactions

Amounts hidden using Pedersen commitments and bulletproof range proofs.

**Transaction privacy:**

* Sender amount: Hidden
* Receiver amount: Hidden
* Transaction balance: Verified cryptographically without revealing values
* Range proofs: Confirm positive amounts without disclosure

**What observers see:**

```
On-chain view:
- Commitment A → Commitment B
- Range proof: ✅ Valid
- Zero amounts visible

Your view:
- Sent: 2.5 ETH
- To: [stealth address]
```

#### Stealth Addresses

One-time recipient addresses derived from meta-address. Sender cannot track, only receiver can detect and claim.

**Protocol (ERC-5564):**

1. Receiver publishes stealth meta-address
2. Sender derives ephemeral one-time address
3. Funds sent to one-time address
4. Receiver scans chain, detects payment, derives private key
5. No public link between meta-address and one-time address

#### Decentralized Relayer Network

Relayers submit withdrawals to prevent IP/timing correlation.

**Architecture:**

* 100+ independent relayers (run by $MACRO stakers)
* Onion routing: Request passes through 3 relayers (entry → middle → exit)
* Tor integration for IP protection
* Batched submissions (10-50 withdrawals bundled)
* Fee paid from shielded balance (no external payment trail)

**Privacy guarantees:**

* No single relayer knows origin, destination, and amount
* Exit relayer submits but cannot correlate with requester
* Randomized delays prevent timing analysis

#### Multi-Hop Routing

For enhanced privacy, route through multiple pools across chains.

**Enhanced unshield:**

```
User balance (Ethereum Pool) → 
Arbitrum Pool (cross-chain bridge) → 
Polygon Pool → 
Unshield via relayer → 
Stealth address
```

Each hop adds entropy and breaks correlation.

### <mark style="color:purple;">How to Use</mark>

#### Shield Assets

**Access:** Wallet Panel → Privacy Layer

**Select asset and amount:**

* Supported: ETH, USDC, USDT, DAI, WBTC
* No minimum (confidential amounts)
* Fee: 0.1%

**Transaction:**

Funds move to shielded pool. Balance encrypted on-chain, visible only to you.

#### Manage Shielded Balance

**Available actions:**

* **Send** - Transfer to stealth addresses (private)
* **Swap** - Exchange assets within pool (confidential)
* **Unshield** - Exit to public address

#### Unshield Options

**Standard (2-5 min):**

* Direct unshield
* Good privacy
* Fee: 0.3%

**Enhanced (30-60 min):**

* Multi-hop routing (3 pools)
* Decentralized relayer submission
* Stealth address
* Fee: 0.5%

**Ultra (1-6 hours):**

* Cross-chain multi-hop
* 5+ relayer hops
* Batched with others
* Random delays
* Fee: 0.8%

#### Claim from Stealth Address

Final step: Claim funds from stealth address to your destination.

**Best practices:**

* Use fresh address
* Wait before exchange deposits
* Enable VPN
* Maintain operational security

### <mark style="color:purple;">Technical Details</mark>

#### Smart Contract Architecture

```solidity
contract MacroShieldedPool {
  mapping(bytes32 => bool) public nullifiers;
  uint256 public merkleRoot;
  
  function shield(uint256 amount) external;
  function transact(bytes zkProof, bytes publicInputs) external;
  function unshield(bytes zkProof, address recipient) external;
}
```

#### ZK Proof System

**Inputs:**

* Public: Nullifiers, commitments, Merkle root
* Private: Amounts, addresses, keys

**Proof:** Valid transaction with balanced inputs/outputs

**Verification:** On-chain verification (\~300k gas)

#### Cryptographic Primitives

**Pedersen commitments:**

```
C = amount * G + blinding * H
```

**Range proofs:** Bulletproofs (\~700 bytes)

**Stealth addresses:** Elliptic curve Diffie-Hellman

**ZK circuits:** Groth16 SNARKs

### Security

#### Threat Model

**Protected against:**

* Chain analysis (Chainalysis, Elliptic)
* Timing analysis
* Amount correlation
* IP tracking
* Graph analysis
* Statistical attacks

**Not protected against:**

* User operational errors
* Compromised devices
* Legal key disclosure

#### Audits

* Trail of Bits (smart contracts)
* OpenZeppelin (smart contracts)
* ABDK (ZK circuits)
* Sigma Prime (ZK circuits)

**Bug bounty:** $500k

### <mark style="color:purple;">Privacy Comparison</mark>

| Feature                | Tornado Cash | Aztec   | Monero | Macro |
| ---------------------- | ------------ | ------- | ------ | ----- |
| Shielded balances      | ❌            | ✅       | ✅      | ✅     |
| Confidential amounts   | ❌            | ✅       | ✅      | ✅     |
| Stealth addresses      | ❌            | ❌       | ✅      | ✅     |
| Decentralized relayers | ❌            | ❌       | N/A    | ✅     |
| Multi-chain routing    | ❌            | Limited | ❌      | ✅     |
| Browser integration    | ❌            | ❌       | ❌      | ✅     |

### Fees

* **Shield:** 0.1%
* **Internal transfer:** 0.05%
* **Unshield (standard):** 0.3%
* **Unshield (enhanced):** 0.5%
* **Unshield (ultra):** 0.8%

Plus gas fees (200k-350k gas depending on operation).

**Fee distribution:**

* 60% to relayer operators
* 20% to liquidity providers
* 20% to protocol treasury

### Legal Considerations

Privacy tools are legal in most jurisdictions. Users responsible for compliance with local laws. Some exchanges flag shielded deposits.

**Macro's position:** Privacy is a right. The mixer is designed for legitimate financial privacy, not illegal activity.

***

**One line:** Shielded pool with confidential transactions, stealth addresses, and decentralized relayers. Monero-level privacy for Ethereum.