# Contract API
### SDK
EVM contracts can program against the [Stork Fast contract'](https://github.com/Stork-Oracle/stork-external/tree/main/chains/evm/contracts/stork_fast)s interface by using the stork-fast-evm-sdk npm package available on [npmjs.com](https://www.npmjs.com/package/@storknetwork/stork-fast-evm-sdk). This SDK provides an interface and useful struct for interacting with the Stork contract. The Stork contract is built using [Hardhat](https://hardhat.org/).
### Getting Started
Solidity
After setting up your Hardhat project, add the stork-fast-evm-sdk to your project dependencies by adding the following line to the `"dependencies"` section of the programs `package.json`
Copy
```json
// package.json
"dependencies": {
"@storknetwork/stork-fast-evm-sdk": "^1.0.0"
}
```
or with the following command:
Copy
```bash
npm i @storknetwork/stork-fast-evm-sdk
```
You can now import the SDK's interface and types with:
Copy
```solidity
// YourContract.sol
import "@storknetwork/stork-fast-evm-sdk/IStorkFast.sol";
import "@storknetwork/stork-fast-evm-sdk/StorkFastStructs.sol";
```
### Concepts
#### Upgradeability
The Stork contract is designed to be upgradeable using [OpenZeppelin's proxy pattern](https://docs.openzeppelin.com/contracts/5.x/learn/upgrading-smart-contracts). Ensure the proxy address remains consistent when interacting with the contract to avoid version mismatches.
#### Usage
In contrast to the Stork Core contract, there is no expectation that users store data on the StorkFast contract. Instead, users should verify a stork update as part of the same transaction used in their application, and only proceed if verification is successful.
### Methods
#### Verify Signed ECDSA Payload
```solidity
function verifySignedECDSAPayload(
bytes calldata payload
) external payable returns (bool);
```
**Description**
Receives a stork batch update and returns a `bool` whether the update is verified or not.
**Parameters**
* `payload`: Packed bytes receivable via the StorkFast [websocket](https://docs.stork.network/resources/stork-fast/websocket-api#signed-ecdsa-message).
**Behavior**
* Verifies the signature of the update batch using the stored EVM public key.
* Only requires one signature verification as the entire batch is signed once.
* Requires sufficient fee based on the number of updates.
**Errors**
* `InvalidPayload (``0x7c6953f9)`: If the update itself is malformed.
* `InsufficientFee (0x025dbdd4)`: If the provided fee is less than the required amount.
#### Verify And Deserialize Signed ECDSA Payload
**Description**
Receives a stork batch update and returns deserialized `StorkAssets` if the update is verifiable.
**Parameters**
* `payload`: Packed bytes receivable via the StorkFast [websocket](https://docs.stork.network/resources/stork-fast/websocket-api#signed-ecdsa-message).
**Behavior**
* Same as Verify Signed ECDSA Payload
* Also returns deserialized data, but reverts on verification failure
**Errors**
* `InvalidPayload (0x7c6953f9)`: If the update itself is malformed.
* `InvalidSignature (0x8baa579f)` : If the signature verification failes.
* `InsufficientFee (0x025dbdd4)`: If the provided fee is less than the required amount.
#### Version
```solidity
function version() public pure returns (string memory);
```
**Description**
Retrieves the current version of the contract.
**Returns**
* `string`: The version string (e.g., "1.0.0").
### Examples
An example contract can be found in the the [stork-external github repo](https://github.com/Stork-Oracle/stork-external/tree/main/chains/evm/examples/stork_fast).
---
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