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This guide walks through onboarding a new user: derive keys, register on-chain, scan for payments, and sweep funds.

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Step 1: One-time key setup

import { OpaqueClient, SETUP_MESSAGE } from "@opaquecash/opaque";

const walletSignature = await walletClient.signMessage({
  account: address,
  message: SETUP_MESSAGE,
});

const client = await OpaqueClient.create({
  chainId: 11155111,
  rpcUrl,
  walletSignature,
  ethereumAddress: address,
  wasmModuleSpecifier: "/pkg/cryptography.js",
  ethereumProvider: window.ethereum,
  solana: { cluster: "devnet" },  // optional, for Solana inbox
});

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Step 2: Register the meta-address

Check registration first: 
const onEth = await client.isMetaAddressRegistered("ethereum");
const onSol = await client.isMetaAddressRegistered("solana");
Register on each chain you want to receive on: 
if (!onEth) {
  const { txHash, metaAddressHex } = await client.registerMetaAddress("ethereum");
  console.log("Registered on Ethereum:", txHash, metaAddressHex);
}

if (!onSol) {
  const { txHash } = await client.registerMetaAddress("solana");
  console.log("Registered on Solana:", txHash);
}
Share client.getMetaAddressHex() with senders who already have your meta-address, or let them resolve via registry: 
const { registered, metaAddressHex } = await client.resolveRecipientMetaAddress(someEoa);

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Step 3: Scan the inbox

const inbox = await client.scan({
  chains: ["ethereum", "solana"],
  fromBlock: 5_000_000n,       // optional EVM lower bound
  includeCrossChain: true,      // merge UAB announcements
});

for (const output of inbox) {
  console.log(output.chain, output.stealthAddress, output.source);
}

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Step 4: Check balances

const balances = await client.getBalancesForOutputs(inbox);

for (const b of balances) {
  console.log(b.chain, b.address, b.nativeRaw.toString());
}
For ERC-20 aggregation on Ethereum (tracked token set): 
import { announcementToIndexerRow } from "@opaquecash/opaque";

const adapter = /* fetch announcements from indexer */;
const rows = announcements.map(announcementToIndexerRow);
const tokenTotals = await client.getBalancesFromAnnouncements(rows);

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Step 5: Sweep to a fresh address

const fresh = "0xYourNewAddress...";

const { tx } = await client.sweep({
  output: inbox[0],
  chain: inbox[0].chain,
  destination: fresh,
});

console.log("Swept:", tx);
sweep reconstructs the one-time stealth private key in WASM and signs a transfer from the stealth address. Never log or persist reconstructed keys beyond your threat model.

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Ghost receive (optional)

For flows where funds arrive before an announcement: 
const ghost = client.prepareGhostReceive();
// Show ghost.stealthAddress to the payer; store ghost.ephemeralPrivateKey securely

// After funds arrive, announce:
const req = client.buildAnnounceTransactionRequestForGhost(ghost.ephemeralPrivateKey);
await walletClient.sendTransaction({ to: req.to, data: req.data });