# check\_has\_key

Public, read-only queries against the Directory contract. No authentication required — works with a standard `Web3` instance.

## Signatures

```python
# check_has_key
def check_has_key(w3: Web3, address: ChecksumAddress) -> bool
async def async_check_has_key(w3: AsyncWeb3, address: ChecksumAddress) -> bool

# get_key_hash
def get_key_hash(w3: Web3, address: ChecksumAddress) -> bytes
async def async_get_key_hash(w3: AsyncWeb3, address: ChecksumAddress) -> bytes
```

## Parameters

| Parameter | Type                 | Description                                            |
| --------- | -------------------- | ------------------------------------------------------ |
| `w3`      | `Web3` / `AsyncWeb3` | Standard Web3 instance (no Seismic namespace required) |
| `address` | `ChecksumAddress`    | Address to query                                       |

## Returns

* **`check_has_key`** — `True` if the address has a registered viewing key
* **`get_key_hash`** — 32-byte `keccak256` hash of the viewing key (zero bytes if no key registered)

## Example

```python
from web3 import Web3
from seismic_web3.src20 import check_has_key, get_key_hash

w3 = Web3(Web3.HTTPProvider("https://gcp-1.seismictest.net/rpc"))
address = "0xf39Fd6e51aad88F6F4ce6aB8827279cffFb92266"

if check_has_key(w3, address):
    key_hash = get_key_hash(w3, address)
    print(f"Key hash: {key_hash.hex()}")
```

## Notes

* Both use plain `eth_call` — no gas cost, no encryption needed
* The key hash is used as the 4th topic in SRC20 Transfer and Approval events for filtering

## See Also

* [register\_viewing\_key](https://docs.seismic.systems/clients/python/src20/intelligence-providers/register-viewing-key) — Register a viewing key
* [get\_viewing\_key](https://docs.seismic.systems/clients/python/src20/intelligence-providers/get-viewing-key) — Fetch your viewing key (authenticated)