StealthAddress

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Overview

• Detect payments to their stealth addresses (using viewing key)
• Spend funds from stealth addresses (using spending key)

• Non-interactive: No communication between sender and recipient required
• Forward secrecy: Past transactions remain private if viewing key compromised
• Unlinkability: Stealth addresses appear unrelated to each other and recipient

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Quick Start

import * as StealthAddress from '@tevm/voltaire/StealthAddress';
import * as Secp256k1 from '@tevm/voltaire/crypto/Secp256k1';

// Generate key pairs
const spendingPrivKey = crypto.getRandomValues(new Uint8Array(32));
const viewingPrivKey = crypto.getRandomValues(new Uint8Array(32));

// Derive public keys
const spendingPubKey = StealthAddress.compressPublicKey(
  Secp256k1.derivePublicKey(spendingPrivKey)
);
const viewingPubKey = StealthAddress.compressPublicKey(
  Secp256k1.derivePublicKey(viewingPrivKey)
);

// Generate meta-address (publish this)
const metaAddress = StealthAddress.generateMetaAddress(
  spendingPubKey,
  viewingPubKey
);

console.log('Meta-address:', Buffer.from(metaAddress).toString('hex'));
// Share meta-address publicly (66 bytes)

import * as StealthAddress from '@tevm/voltaire/StealthAddress';

// Get recipient's published meta-address
const metaAddress = recipientMetaAddress; // 66 bytes

// Generate ephemeral key
const ephemeralPrivKey = crypto.getRandomValues(new Uint8Array(32));

// Generate stealth address
const result = StealthAddress.generateStealthAddress(
  metaAddress,
  ephemeralPrivKey
);

console.log('Stealth address:', Buffer.from(result.stealthAddress).toString('hex'));
console.log('Ephemeral pubkey:', Buffer.from(result.ephemeralPublicKey).toString('hex'));
console.log('View tag:', result.viewTag);

// Publish announcement: ephemeralPublicKey + viewTag
// Send funds to stealthAddress

import * as StealthAddress from '@tevm/voltaire/StealthAddress';

// Scan announcements from blockchain
const announcements = await fetchStealthAnnouncements();

for (const { ephemeralPubKey, viewTag, stealthAddr } of announcements) {
  // Quick check using view tag (1 byte)
  const expectedViewTag = StealthAddress.computeViewTag(
    viewingPrivKey,
    ephemeralPubKey
  );

  if (viewTag !== expectedViewTag) {
    continue; // Not for us, skip expensive check
  }

  // Full check (more expensive)
  const result = StealthAddress.checkStealthAddress(
    viewingPrivKey,
    ephemeralPubKey,
    viewTag,
    spendingPubKey,
    stealthAddr
  );

  if (result.isForRecipient) {
    // Compute spending key for this stealth address
    const stealthPrivKey = StealthAddress.computeStealthPrivateKey(
      spendingPrivKey,
      result.stealthPrivateKey
    );

    // Can now spend funds from stealthAddr using stealthPrivKey
    console.log('Found payment! Can spend from:', stealthAddr);
  }
}

​

How It Works

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1. Setup (Recipient)

• Spending keys: For spending funds (keep spending private key secret)
• Viewing keys: For scanning blockchain (can be delegated to scanner)

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2. Payment (Sender)

1. Generate ephemeral key pair
2. Perform ECDH with recipient’s spending public key
3. Derive stealth address using keccak256
4. Generate 1-byte view tag for efficient scanning
5. Publish ephemeral public key and view tag (announcement)
6. Send payment to stealth address

​

3. Detection (Recipient)

1. Check view tag first (cheap 1-byte comparison)
2. If view tag matches, perform full check (ECDH + address derivation)
3. If match confirmed, compute stealth private key for spending

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API Documentation

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View Tags Optimization

// Without view tag: Check every announcement (expensive)
for (const announcement of announcements) {
  // Perform full ECDH + derivation (~1000 gas equivalent)
  const result = checkStealthAddress(...);
}

// With view tag: Filter first (cheap)
for (const { viewTag, ...announcement } of announcements) {
  const expected = computeViewTag(viewingPrivKey, ephemeralPubKey);
  if (viewTag !== expected) continue; // Skip 99% of announcements

  // Only check 1% that match view tag
  const result = checkStealthAddress(...);
}

​

Privacy Considerations

• Viewing key compromise: Past stealth addresses remain private
• Spending key compromise: Catastrophic (all funds at risk)
• Best practice: Use hardware wallet for spending key

• Transaction amounts visible on-chain
• Timing correlation possible
• Consider mixing with other privacy techniques

• Spending key: Never expose (offline/hardware wallet)
• Viewing key: Can delegate to scanner service
• Ephemeral keys: Generate fresh for each payment

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Specification References

• ERC-5564 - Stealth Address specification
• ERC-6538 - Stealth Meta-Address Registry
• Stealth Addresses Research

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Related

• Secp256k1 - Elliptic curve operations
• Keccak256 - Hash function for derivation
• Address - Ethereum address utilities