# Register your viewing key on-chain

> Publish your viewing public key to the keystore so others can send you discoverable notes (no out-of-band hand-off).

## What this lets you do

Publish your viewing public key into the on-chain [keystore](/protocol/contracts/keystore) contract. Once registered, senders can encrypt note payloads directly to you: no need to share secrets [out-of-band](/concepts/discoverable-vs-oob), no need for you to do anything per incoming payment. Your `discoverNotes()` just finds them.

## Constraints & limits

-   **Two on-chain transactions:** `setAuthPolicy` and `setViewingKey`, both signed by your wallet. The gas is a one-time cost that varies with network conditions.
-   **Public:** the pairing of your viewing pubkey and wallet address is permanently on-chain. Anyone scanning the chain can know "address X has registered for shielded receives."
-   **Per-address:** registration is keyed by your EVM address, so moving to a different wallet means registering again with that wallet's derived viewing key. That is separate from rotating keys on the same wallet: you can [rotate your revocable key](/operations/rotate-revocable-key) in place without re-registering.
-   **X25519 format:** the viewing pubkey must be 32 bytes.

## What it unlocks next

-   Discoverable mode for [private transfers](/operations/transfer) sent to this address, so senders no longer need to pass you the noteSecret.
-   [Payment requests](/operations/payment-requests) with tag-targeted on-chain delivery.

## How to use it

```ts
// Check first to avoid paying gas twice. The session knows its own
// ownerAddress, so this method takes no arguments.
const registered = await session.isKeystoreRegistered();
if (!registered) {
    const result = await session.registerKeystore();
    // result contains both tx receipts (setAuthPolicy + setViewingKey)
    console.log("registered:", result);
}
```

**Trade-off to think about:** registration adds public surface (everyone can see that your address uses Privacy Pools) in exchange for receive-side UX (no OoB hand-off per payment). For payroll-style "I send to lots of people, they don't all want to register," consider the [receipt model](../operations/generate-receipt) instead, where recipients claim their notes from the receipt without registering.

## Behind the scenes

SDK call `session.registerKeystore()`
Contract methods `Keystore.setAuthPolicy(...)` then `Keystore.setViewingKey(...)`
On-chain effect `setAuthPolicy` inserts your auth-policy leaf into the [keystore tree](/concepts/keystore-tree), and `setViewingKey` records your viewing pubkey in the separate `viewingKeys(address)` mapping (the viewing key is not a tree leaf). Future `prepareTransfer` calls with `recipientDiscoveryData: {evmAddress: you}` then resolve your viewing key and use discoverable mode.