This document discusses two-factor authentication and its benefits. It describes two-factor authentication as requiring two different types of evidence, such as something you know (a password) and something you have (a token or mobile device). Hard tokens generate one-time passwords on a physical device while mobile tokens use a mobile app to generate passwords. Using a mobile token is more flexible and cheaper than hard tokens but still vulnerable to active attacks. Sending a one-time password via SMS and requiring the user to enter a code for transactions adds an extra layer of security against man-in-the-middle attacks compared to other methods. The document recommends hashing passwords before sending and mutual authentication between clients and servers to improve security.