using System;

using System.Security.Cryptography;

public class Program

{

    public static void Main()

    {

        var key = "hello";

        var hashAlgorithm = new SHA256CryptoServiceProvider();

        byte[] byteValue = System.Text.Encoding.UTF8.GetBytes(key);

        byte[] byteHash = hashAlgorithm.ComputeHash(byteValue);

        var res = Convert.ToBase64String(byteHash);

        Console.WriteLine(res);

    }

}