def compare(crypted_string, plain_string)
      BCrypt::Password.new(crypted_string).is_password?(plain_string)
    rescue BCrypt::Errors::InvalidHash
      false
    end
def compare(crypted_string, plain_string)
      BCrypt::Password.new(crypted_string).is_password?(plain_string)
    rescue BCrypt::Errors::InvalidHash
      false
    end
Returns true if the the bcrypted value of a is equal to b