# Register

> Register your viewing key in the privacy pool with the builder or autoRegister

Before an account can receive private transfers it must **register**: publish
its public viewing key on-chain and store the auditor-encrypted private key.

Because the registered public viewing key is immutable, persist and back up the
matching private viewing key before the account receives meaningful shielded
funds. Wallet products should expose a per-account export and recovery flow; see
[Viewing Keys & Backups](/viewing-keys).

This happens once per account per pool deployment.

Snippets assume `transfers`, `account` and `provider` from
[Getting Started](/sdk/getting-started).

```typescript
const provingBlockId = (await provider.getBlockNumber()) - 10

const { callAndProof } = await transfers.build().register().execute({ provingBlockId })

// Submission tail (explained in Getting Started)
const proofDetails = callAndProof.proof.proofFacts?.length
  ? { proofFacts: callAndProof.proof.proofFacts, proof: callAndProof.proof.data }
  : {}
const tx = await account.execute(callAndProof.call, { tip: 0n, ...proofDetails })
await provider.waitForTransaction(tx.transaction_hash)
```

## Things to notice

- You never pass the viewing key to `register()`. The builder pulls it from
  the `viewingKeyProvider` you wired into `createPrivateTransfers`.
- The viewing key must be a **`BigInt`** in the range `[1, MAX_VIEWING_KEY]`
  (half the STARK curve order, exported by the SDK). A hex string compiles
  fine but silently derives wrong channel keys - notes sent to you will never
  decrypt.
- Registering twice reverts. Check first, or use `autoRegister` below.

## `autoRegister`

Instead of registering as its own transaction, any build can bundle the
registration in automatically when the account has no viewing key on-chain
yet:

```typescript
const { callAndProof } = await transfers
  .build({ autoRegister: true })
  .with(tokenAddress, (t) => t.deposit({ amount: 100n }))
  .surplusTo(account.address)
  .execute({ provingBlockId })
```

If the account is already registered, `autoRegister` is a no-op - safe to
leave on for first-time-user flows (a claim page, an onboarding deposit).

| Approach             | When to use                                              |
| -------------------- | -------------------------------------------------------- |
| `.register()`        | Explicit onboarding step, dedicated "register" button    |
| `autoRegister: true` | Bundle registration into the user's first real operation |

Next: [Deposit](/sdk/deposit) public ERC-20 tokens into the pool.