Stealth Addresses

const signature = await wallet.signMessage("UPP Stealth Key Derivation v1")
const seed = keccak256(signature)

// Spending key — authorizes spending notes
const spendingSecret = keccak256(seed + "spending:v1") % SUBGROUP_ORDER
const spendingPub = spendingSecret * G

// Viewing key — decrypts notes (share for auditing without risking funds)
const viewingSecret = keccak256(seed + "viewing:v1") % SUBGROUP_ORDER
const viewingPub = viewingSecret * G

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// 1. Generate ephemeral keypair (fresh random each payment)
const r = randomScalar()
const R = r * G

// 2. ECDH shared secret with recipient's viewing key
const shared = r * recipientViewingPub

// 3. Encrypt note with derived secret
const ciphertext = encrypt(shared, noteData)

// 4. Include R in the output — recipient needs it to decrypt
return { commitment, ciphertext, R }

// Scan all note events on-chain
for (const event of noteEvents) {
  const R = decodePoint(event.encryptedData)

  // Compute shared secret with your viewing key
  const shared = viewingSecret * R

  // Try to decrypt — if it fails, note is not yours
  try {
    const note = decrypt(shared, event.ciphertext)
    if (verifyCommitment(note, event.commitment)) {
      myNotes.push(note)
    }
  } catch {
    // Not for us — continue scanning
  }
}