C# BCRYPT.Net cost calculator

BcryptNetCostCalculator.cs

namespace BcryptPerformanceTestCSharpDotNet
{
    using System;
    using System.Diagnostics;
    using BCrypt.Net;

    /// <summary>
    /// C# BCRYPT.Net cost calculator 
    /// You will need BCrypt.Net-Next Nugget: https://www.nuget.org/packages/BCrypt.Net-Next/
    /// </summary>
    class Program
    {
        static void Main(string[] args)
        {
            int cost = 3;
            int first_cost_above_100 = 0;
            int first_cost_above_500 = 0;
            long upperTimeLimit = 1000;
            string password = "this_is_just_a_long_string_to_test_on_U8WNZqmz8ZVBNiNTQR8r";

            Console.WriteLine("\nPassword BCRYPT.Net Hash Cost Calculator\n\n");
            Console.WriteLine($"We're going to run until the time to generate the hash takes longer than {upperTimeLimit}ms\n");

            long time;
            Stopwatch stopwatch = new Stopwatch();
            do
            {
                cost += 1;
                Console.Write($"\nTesting cost value of {cost}: ");

                stopwatch.Restart();
                BCrypt.HashPassword(password, cost);
                stopwatch.Stop();

                time = stopwatch.ElapsedMilliseconds;

                Console.Write($"... took {time}ms");

                if (first_cost_above_100 == 0 && time > 100) 
                {
                    first_cost_above_100 = cost;
                } else if (first_cost_above_500 == 0 && time > 500)
                {
                    first_cost_above_500 = cost;
                }

            } while (time < upperTimeLimit);

            Console.WriteLine($"\n\n\nYou should use a cost between {first_cost_above_100} and {first_cost_above_500}");
            Console.ReadLine();
        }
    }
}

Example output:

Password BCRYPT.Net Hash Cost Calculator


We're going to run until the time to generate the hash takes longer than 1000ms


Testing cost value of 4: ... took 29ms
Testing cost value of 5: ... took 4ms
Testing cost value of 6: ... took 8ms
Testing cost value of 7: ... took 16ms
Testing cost value of 8: ... took 32ms
Testing cost value of 9: ... took 64ms
Testing cost value of 10: ... took 129ms
Testing cost value of 11: ... took 256ms
Testing cost value of 12: ... took 514ms
Testing cost value of 13: ... took 1033ms


You should use a cost between 10 and 12

Note: first value seems to be an outlier...