Secp256k1.sol

// SPDX-License-Identifier: MIT

pragma solidity ^0.8.0;

import "elliptic-curve-solidity/contracts/EllipticCurve.sol";

/**
 ** @title Secp256k1 Elliptic Curve
 ** @notice Example of particularization of Elliptic Curve for secp256k1 curve
 ** @author Witnet Foundation
 */
contract Secp256k1 {
    uint256 public constant GX =
        0x79BE667EF9DCBBAC55A06295CE870B07029BFCDB2DCE28D959F2815B16F81798;
    uint256 public constant GY =
        0x483ADA7726A3C4655DA4FBFC0E1108A8FD17B448A68554199C47D08FFB10D4B8;
    uint256 public constant AA = 0;
    uint256 public constant BB = 7;
    uint256 public constant PP =
        0xFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFEFFFFFC2F;

    /// @notice Public Key derivation from private key
    /// Warning: this is just an example. Do not expose your private key.
    /// @param privKey The private key
    /// @return (qx, qy) The Public Key
    function derivePubKey(
        uint256 privKey
    ) external pure returns (uint256, uint256) {
        return EllipticCurve.ecMul(privKey, GX, GY, AA, PP);
    }
}