# SeismicElements

Seismic-specific fields appended to every `TxSeismic` transaction. These carry the encryption parameters and block-expiry metadata.

## Definition

```python
@dataclass(frozen=True)
class SeismicElements:
    encryption_pubkey: CompressedPublicKey
    encryption_nonce: EncryptionNonce
    message_version: int
    recent_block_hash: Bytes32
    expires_at_block: int
    signed_read: bool
```

## Fields

| Field               | Type                                                                                                           | Description                                                |
| ------------------- | -------------------------------------------------------------------------------------------------------------- | ---------------------------------------------------------- |
| `encryption_pubkey` | [`CompressedPublicKey`](https://docs.seismic.systems/clients/python/api-reference/types/compressed-public-key) | TEE's compressed secp256k1 key for ECDH-derived encryption |
| `encryption_nonce`  | [`EncryptionNonce`](https://docs.seismic.systems/clients/python/api-reference/types/encryption-nonce)          | 12-byte AES-GCM nonce                                      |
| `message_version`   | `int`                                                                                                          | Signing mode — `0` for raw, `2` for EIP-712                |
| `recent_block_hash` | [`Bytes32`](https://docs.seismic.systems/clients/python/api-reference/types/bytes32)                           | Hash of a recent block (freshness proof)                   |
| `expires_at_block`  | `int`                                                                                                          | Block number after which the tx is invalid                 |
| `signed_read`       | `bool`                                                                                                         | `True` for signed `eth_call` reads, `False` for writes     |

## Example

```python
from seismic_web3 import (
    SeismicElements,
    CompressedPublicKey,
    EncryptionNonce,
    Bytes32,
)
import os

elements = SeismicElements(
    encryption_pubkey=CompressedPublicKey(...),  # from get_tee_public_key()
    encryption_nonce=EncryptionNonce(os.urandom(12)),
    message_version=2,
    recent_block_hash=Bytes32(...),
    expires_at_block=12345678,
    signed_read=False,
)
```

In practice the SDK constructs `SeismicElements` automatically — override specific fields via [`SeismicSecurityParams`](https://docs.seismic.systems/clients/python/api-reference/transaction-types/seismic-security-params).

## See Also

* [SeismicSecurityParams](https://docs.seismic.systems/clients/python/api-reference/transaction-types/seismic-security-params) — user-facing overrides for defaults
* [UnsignedSeismicTx](https://docs.seismic.systems/clients/python/api-reference/transaction-types/unsigned-seismic-tx) — contains SeismicElements
* [TxSeismicMetadata](https://docs.seismic.systems/clients/python/api-reference/transaction-types/tx-seismic-metadata) — uses SeismicElements for AAD