rustywallet-silent

Silent Payments (BIP352) implementation for rustywallet.

Overview

Silent Payments allow receivers to publish a single static address while each payment generates a unique on-chain address that only the receiver can detect and spend. This provides significant privacy benefits compared to address reuse.

Features

• Silent Payment Address: Generate and parse sp1/tsp1 addresses
• Payment Derivation: ECDH-based output key derivation
• Scanning: Detect incoming payments to your silent payment address
• Sending: Create outputs for silent payment recipients
• Labels: Support for multiple labeled addresses from single key
• Change Handling: Proper change output derivation

Usage

use rustywallet_silent::prelude::*;
use rustywallet_keys::prelude::PrivateKey;

// Generate Silent Payment keys
let scan_key = PrivateKey::random();
let spend_key = PrivateKey::random();

// Create Silent Payment address
let sp_address = SilentPaymentAddress::new(
    &scan_key.public_key(),
    &spend_key.public_key(),
    Network::Mainnet,
).unwrap();

println!("Silent Payment Address: {}", sp_address);

// Sender: Create payment output
let sender_keys = vec![PrivateKey::random()];
let outpoints = vec![([0u8; 32], 0u32)];

let outputs = create_outputs(
    &sender_keys,
    &outpoints,
    &[sp_address.clone()],
).unwrap();

// Receiver: Scan for payments
let scanner = SilentPaymentScanner::new(&scan_key, &spend_key.public_key());
let found = scanner.scan_outputs(&outputs, &outpoints).unwrap();

Protocol Overview

Address Format

Silent Payment addresses use bech32m encoding:

• Mainnet: sp1...
• Testnet: tsp1...

The address contains two public keys:

• Scan key (B_scan): Used to detect incoming payments
• Spend key (B_spend): Used to derive spending keys

Sending

1. Collect all input private keys
2. Compute input hash from outpoints
3. For each recipient, compute shared secret via ECDH
4. Derive output public key: P_output = B_spend + hash(shared_secret || n) * G

Receiving

1. For each transaction output, compute potential shared secret
2. Check if output matches derived key
3. If match found, compute spending private key

Security Considerations

• Scan key can be shared with a light client for detection
• Spend key must remain secret
• Each payment creates a unique address (no address reuse)
• Labels allow multiple addresses without additional keys

License

MIT