Introduction “Please enter the code we just sent you.” – most people have seen this message when logging into an online service. Two-Factor Authentication (2FA) is no longer reserved for banks or enterprises. It’s now common in email, social media, and shopping accounts. The idea is simple: in addition to a password, you need a second factor so that attackers can’t break in with just one piece of information. But what methods are actually used – and how secure are they really? At ...
