# Precompiles

## Currency Swap precompile

Use this precompile to transfer the funds from your EVM account to any Native account.

<table><thead><tr><th width="150">Property</th><th width="583.1428571428571">Description</th></tr></thead><tbody><tr><td>Address</td><td><code>0x0000000000000000000000000000000000000900</code></td></tr><tr><td>Input</td><td>See contract interface.</td></tr><tr><td>Output</td><td>See contract interface.</td></tr></tbody></table>

### Contract interface

<https://github.com/humanode-network/humanode/blob/master/crates/precompile-currency-swap/CurrencySwap.sol>

```solidity
// SPDX-License-Identifier: UNLICENSED

pragma solidity >=0.7.0 <0.9.0;

/**
 * @title Currency Swap Interface
 *
 * An interface enabling swapping the funds from EVM accounts to
 * native Substrate accounts.
 *
 * Address: 0x0000000000000000000000000000000000000900
 */
interface CurrencySwap {
  /**
   * Transfer the funds from an EVM account to native substrate account.
   * Selector: 76467cbd
   *
   * @param nativeAddress The native address to send the funds to.
   * @return success Whether or not the swap was successful.
   */
  function swap(bytes32 nativeAddress) external payable returns (bool success);
}
```

## Bioauth status check precompile

Use this precompile to check if the specified address has an active bioauth. Takes the validator public key (type `AccountId` in the Humanode runtime code, also known as native - or Substrate - account).

<table><thead><tr><th width="150">Property</th><th width="583.1428571428571">Description</th></tr></thead><tbody><tr><td>Address</td><td><code>0x0000000000000000000000000000000000000800</code></td></tr><tr><td>Input</td><td><code>AccountId</code> (Substrate account address); 32 bytes<br>The public key to check.</td></tr><tr><td>Output</td><td><code>bool</code>; 1 byte<br><code>1</code> if bioauth is active for the address, <code>0</code> if bioauth is inactive for the address.</td></tr></tbody></table>

### Helper Library

You can use the helper library below together with your smart contract code to simplify invoking the precompile.

```solidity
// SPDX-License-Identifier: UNLICENSED

pragma solidity ^0.8.0;

library bioauth {
    function isAuthenticated(bytes32 accountId) public view returns (bool result) {
        address precompile = 0x0000000000000000000000000000000000000800;
        bytes memory payload = abi.encodePacked(accountId);
        (bool success, bytes memory returnData) = precompile.staticcall(payload);
        assert(success);
        assert(returnData.length == 1);
        return (returnData[0] != 0);
    }
}
```

## EVM to native account mapping precompile

Use this precompile to find a corresponding mapped native `AccountId` for provided EVM address. This is useful to be used in combination with `Bioauth` precompile as you don't need to worry about a proper `AccountId` to do bioauth check.

Description

<table><thead><tr><th width="150">Property</th><th width="583.1428571428571">Description</th></tr></thead><tbody><tr><td>Address</td><td><code>0x0000000000000000000000000000000000000801</code></td></tr><tr><td>Input</td><td><code>evmAddress</code> (EVM address); 20 bytes</td></tr><tr><td>Output</td><td><p><code>(bool, bytes32)</code>; </p><ul><li><code>(true, 0x12..9)</code>: indicates that the evm adress has been mapped where <code>0x12..9</code> is the mapped native account itself. </li><li><code>(false, 0x00..0)</code>: indicates that the evm addres hasn't been mapped.</li></ul></td></tr></tbody></table>

### Helper Library

You can use the helper library below together with your smart contract code to simplify invoking the precompile.

```solidity
// SPDX-License-Identifier: UNLICENSED

pragma solidity ^0.8.0;

library evmAccounts {
    function claimedNativeAccount(bytes20 evmAddress) public view returns (bool, bytes32) {
        address precompile = 0x0000000000000000000000000000000000000801;
        bytes memory payload = abi.encodePacked(evmAddress);
        (bool success, bytes memory returnData) = precompile.staticcall(payload);
        assert(success);
        if (returnData.length == 0) {
            return (false, 0x0);
        } 
        bytes32 nativeAccount = abi.decode(returnData, (bytes32));
        return (true, nativeAccount);
    }
}
```