Question

I am currently working on a Log in form but the thing here is that when I enter an invalid username this errors comes up.

Invalid length for a Base-64 char array.

On this line of code:

bool isSame = hasher.CompareStringToHash(txtPassword.Text, hashedPassword);

Here is the full code

public void verifyAccount()
        {
            var hashedPassword = getPassword();

            var hasher = new Hasher();

            hasher.SaltSize = 16;
            bool isSame = hasher.CompareStringToHash(txtPassword.Text, hashedPassword);

            if (isSame==false)
            {
                MessageBox.Show("Invalid UserName or Password");
            }
            else
            {
                MainWindow main = new MainWindow();
                this.Hide();
                main.ShowDialog();
                this.Close();
            }   
        }

And the This is the method for searching a such username at the same time getting their password password in the database.

public string getPassword()
        {

            DataClasses1DataContext myDbContext = new DataClasses1DataContext(dbPath);


            var password = (from user in myDbContext.Accounts
                           where user.accnt_User == txtUser.Text
                           select user.accnt_Pass).FirstOrDefault();

             if (password == null) {
                 return "z"; 
             }

            return password;
        }

Answer 1

Base64 data should be 4-bytes aligned. So for example the “z” that you’re returning should be Base64 encoded and padded like this: “eg==” to be Base64 compliant. You should do the same type of padding for the real hashed password.