using System;

using System.Security.Cryptography;

public class Program

{

    public static bool Login(string password, Tuple<string, string> user)

    {

        if (!VerifyPasswordHash(password, Convert.FromBase64String(user.Item1),

            Convert.FromBase64String(user.Item2)))

            return false;

        return true;

​

    }

    // this method is used to verify the password 

    private static  bool VerifyPasswordHash(string password, byte[] passwordHash, byte[] passwordSalt)

    {

        using (var hmac = new System.Security.Cryptography.HMACSHA512(passwordSalt))

        {

            //changes the string into byte and them computes the hash

            byte[] computedHash = hmac.ComputeHash(System.Text.Encoding.UTF8.GetBytes(password));

            for (int i = 0; i < computedHash.Length; i++)

            {

                //compares the hashed password(user input) with the hashed password from the database

                if (computedHash[i] != passwordHash[i])

                    return false;

            }

        }

        return true;

    }

    // This method is used to register the users

    public static Tuple<string, string> Register(string password)

    {

        byte[] passwordHash, passwordSalt;

        CreatePasswordHash(password, out passwordHash, out passwordSalt);

​

        return new Tuple<string, string>( Convert.ToBase64String(passwordHash), Convert.ToBase64String(passwordSalt) );

    }

​

    private static void CreatePasswordHash(string password, out byte[] passwordHash, out byte[] passwordSalt)

    {

        using (var hmac = new System.Security.Cryptography.HMACSHA512())

        {

            passwordSalt = hmac.Key;

            passwordHash = hmac.ComputeHash(System.Text.Encoding.UTF8.GetBytes(password));

        }

    }

    public static void Main()

    {

        string username = "foo";

        string password = "qqq";

        Tuple<string, string> r = Register( password );

        Console.WriteLine( r.Item1 );

        Console.WriteLine( r.Item2 );

        Console.WriteLine( Login( password, r ));

    }

}