> For the complete documentation index, see [llms.txt](https://docs.coti.io/coti-documentation/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.coti.io/coti-documentation/how-coti-works/advanced-topics/precompiles.md).

# Precompiles

## MpcInterface.sol

The `MpcInterface` contract is a precompiled contract used by the gcEVM to facilitate multi-party computations (MPC). It is deployed at the fixed address: `0x0000000000000000000000000000000000000064`.

The contract implements the following interface:

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

pragma solidity ^0.8.19;

interface ExtendedOperations {

    function OnBoard(bytes1 metaData, uint256 ct) external returns (uint256 result);
    function OffBoard(bytes1 metaData, uint256 ct) external returns (uint256 result);
    function OffBoardToUser(bytes1 metaData, uint256 ct, bytes calldata addr) external returns (uint256 result);
    function SetPublic(bytes1 metaData, uint256 ct) external returns (uint256 result);
    function Rand(bytes1 metaData) external returns (uint256 result);
    function RandBoundedBits(bytes1 metaData, uint8 numBits) external returns (uint256 result);
    function Add(bytes3 metaData, uint256 lhs, uint256 rhs) external returns (uint256 result);
    function CheckedAdd(bytes3 metaData, uint256 lhs, uint256 rhs) external returns (uint256 overflowBit, uint256 result);
    function Sub(bytes3 metaData, uint256 lhs, uint256 rhs) external returns (uint256 result);
    function CheckedSub(bytes3 metaData, uint256 lhs, uint256 rhs) external returns (uint256 overflowBit, uint256 result);
    function Mul(bytes3 metaData, uint256 lhs, uint256 rhs) external returns (uint256 result);
    function CheckedMul(bytes3 metaData, uint256 lhs, uint256 rhs) external returns (uint256 overflowBit, uint256 result);
    function Div(bytes3 metaData, uint256 lhs, uint256 rhs) external returns (uint256 result);
    function Rem(bytes3 metaData, uint256 lhs, uint256 rhs) external returns (uint256 result);
    function And(bytes3 metaData, uint256 lhs, uint256 rhs) external returns (uint256 result);
    function Or(bytes3 metaData, uint256 lhs, uint256 rhs) external returns (uint256 result);
    function Xor(bytes3 metaData, uint256 lhs, uint256 rhs) external returns (uint256 result);
    function Shl(bytes3 metaData, uint256 lhs, uint256 rhs) external returns (uint256 result);
    function Shr(bytes3 metaData, uint256 lhs, uint256 rhs) external returns (uint256 result);
    function Eq(bytes3 metaData, uint256 lhs, uint256 rhs) external returns (uint256 result);
    function Ne(bytes3 metaData, uint256 lhs, uint256 rhs) external returns (uint256 result);
    function Ge(bytes3 metaData, uint256 lhs, uint256 rhs) external returns (uint256 result);
    function Gt(bytes3 metaData, uint256 lhs, uint256 rhs) external returns (uint256 result);
    function Le(bytes3 metaData, uint256 lhs, uint256 rhs) external returns (uint256 result);
    function Lt(bytes3 metaData, uint256 lhs, uint256 rhs) external returns (uint256 result);
    function Min(bytes3 metaData, uint256 lhs, uint256 rhs) external returns (uint256 result);
    function Max(bytes3 metaData, uint256 lhs, uint256 rhs) external returns (uint256 result);
    function Decrypt(bytes1 metaData, uint256 a) external returns (uint256 result);
    function Mux(bytes3 metaData, uint256 bit, uint256 a,uint256 b) external returns (uint256 result);
    function Not(bytes1 metaData, uint256 a) external returns (uint256 result);
    function Transfer(bytes4 metaData, uint256 a, uint256 b, uint256 amount) external returns (uint256 new_a, uint256 new_b, uint256 res);
    function TransferWithAllowance(bytes5 metaData, uint256 a, uint256 b, uint256 amount, uint256 allowance) external returns (uint256 new_a, uint256 new_b, uint256 res, uint256 new_allowance);
    function ValidateCiphertext(bytes1 metaData, uint256 ciphertext, bytes calldata signature) external returns (uint256 result);
    function GetUserKey(bytes calldata signedEK) external returns (bytes memory encryptedKey);
    function SHA256Fixed432BitInput(uint256 amount, uint256 seed1, uint256 seed2, uint256 padding1, uint256 padding2, bytes calldata addr) external returns (bytes memory result);
}
```

The `metaData` values are designed to combine multiple enum values into bytes for efficient storage and transfer. For more information about the required format of `metaData` values, see the [MPC Core documentation](/coti-documentation/build-on-coti/tools/contracts-library/mpc-core.md#encoding-functions).


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