using System;

// using System.Net;

// using System.Net.Http;

using System.Security.Cryptography;

using System.Text;

public class Program

{

    static string apiPublicKey = "API_PUBLIC_KEY";

    // Hardcoce API_PRIVATE_KEY base 64 value

    static string apiPrivateKey = Base64EncodeString("some_api_key_1234");

    static string endPoint = "https://www.website.com/getToken";

​

    public static void Main()

    {

        Console.WriteLine("API-Sign: '{0}'", GenApiSign());

    }

​

    static private string GenApiSign()

    {

        // string ApiNonce = DateTimeOffset.Now.ToUnixTimeMilliseconds().ToString();

        // Hardcode the time so we can confirm the same result with Python

        string ApiNonce = "1586096626919";

​

        Console.WriteLine("API nonce: {0}", ApiNonce);

        Console.WriteLine("API_PRIVATE_KEY: '{0}'", apiPrivateKey);

​

        byte[] ApiNonceBytes = Encoding.Default.GetBytes(ApiNonce);

​

        byte[] h256Dig = GenerateSHA256(CombineBytes(ApiNonceBytes, Encoding.Default.GetBytes("nonce="), ApiNonceBytes));

        byte[] h256Token = CombineBytes(Encoding.Default.GetBytes("/getToken"), h256Dig);

​

        string ApiSign = Base64Encode(GenerateSHA512(Base64Decode(apiPrivateKey), h256Token));

​

        return ApiSign;

    }

​

    // Helper functions ______________________________________________________________________________________

​

    public static byte[] CombineBytes(byte[] first, byte[] second)

    {

        byte[] ret = new byte[first.Length + second.Length];

        Buffer.BlockCopy(first, 0, ret, 0, first.Length);

        Buffer.BlockCopy(second, 0, ret, first.Length, second.Length);

        return ret;

    }

​

    public static byte[] CombineBytes(byte[] first, byte[] second, byte[] third)

    {

        byte[] ret = new byte[first.Length + second.Length + third.Length];

        Buffer.BlockCopy(first, 0, ret, 0, first.Length);

        Buffer.BlockCopy(second, 0, ret, first.Length, second.Length);

        Buffer.BlockCopy(third, 0, ret, first.Length + second.Length,

                         third.Length);

        return ret;

    }

​

​

    public static byte[] GenerateSHA256(byte[] bytes)

    {

        SHA256 sha256 = SHA256Managed.Create();

        return sha256.ComputeHash(bytes);

    }

​

    public static byte[] GenerateSHA512(byte[] key, byte[] bytes)

    {

        var hash = new HMACSHA512(key);

        var result = hash.ComputeHash(bytes);

​

        hash.Dispose();

​

        return result;

    }

​

    public static string Base64EncodeString(string plainText)

    {

        var plainTextBytes = System.Text.Encoding.UTF8.GetBytes(plainText);

        return System.Convert.ToBase64String(plainTextBytes);

    }

​

    public static string Base64Encode(byte[] bytes)

    {

        return System.Convert.ToBase64String(bytes);

    }

​

    public static byte[] Base64Decode(string base64EncodedData)

    {

        var base64EncodedBytes = System.Convert.FromBase64String(base64EncodedData);

        return base64EncodedBytes;

    }

}