# Privacy Model

#### What's Private?

#### ✅ Fully Private (Zero-Knowledge)

| Data                    | Privacy Level     | Explanation                                              |
| ----------------------- | ----------------- | -------------------------------------------------------- |
| **Payment Amount**      | Fully Encrypted   | ElGamal encryption - only sender & recipient can decrypt |
| **Sender Identity**     | Zero-Knowledge    | ZK proof doesn't reveal sender wallet address            |
| **Sender Balance**      | Hidden            | Proof shows sufficient funds without revealing amount    |
| **Phone Number**        | Encrypted Mapping | Phone-to-wallet link encrypted on-chain                  |
| **Transaction Pattern** | Obfuscated        | Multiple transactions indistinguishable                  |

#### ⚠️ Partially Private

| Data                     | Visibility | Explanation                                       |
| ------------------------ | ---------- | ------------------------------------------------- |
| **Recipient Address**    | Public     | Merchant/payee wallet address visible (by design) |
| **Resource URL**         | Public     | What's being paid for is visible                  |
| **Timestamp**            | Public     | When payment occurred is visible                  |
| **Transaction Occurred** | Public     | That a payment happened is visible (not amount)   |

#### 🔓 Public (By Design)

* **Merchant phone/wallet**: Receivers need to be identifiable
* **Smart contract address**: Program execution is transparent
* **Network fees**: Blockchain operation costs (absorbed by NumPay)

### Privacy Technology Stack

<figure><img src="/files/LdXx8TAiAz5FWt0RKvwm" alt=""><figcaption></figcaption></figure>

#### Privacy Guarantees

**Sender Privacy**

* ✓ Payment amount is hidden from public observers
* ✓ Sender wallet address not revealed in ZK proof
* ✓ Account balance not disclosed
* ✓ Phone number never exposed publicly

**Recipient Privacy**

* ✓ Can receive payments to phone number (encrypted mapping)
* ⚠️ Wallet address visible (required for payment receipt)
* ✓ Individual payment amounts hidden from public
* ✓ Total received amount not publicly calculable

**Observer Privacy**

* ✗ Can see a payment occurred
* ✗ Can see merchant address
* ✗ Can see resource URL
* ✓ Cannot see payment amount
* ✓ Cannot link sender identity
* ✓ Cannot calculate transaction patterns


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