A few months back, I obtained two Yubikeys, one master and one as a backup, to use as two-factor devices. I specifically acquired the Yubikey 5C NFC. The result was me going down the rabbit hole to know more about how the key works, the protocols, and the setup. A by-product is this blog post.

A few weeks ago, I became curious about the one-time password algorithms and how two-factor authentication works behind the scenes with the various providers, i.e., Google Authenticator or OTP Yubikey. Nowadays, I believe everyone or almost everyone is using two-factor authentication (2FA). Two-factor authentication is a specific type of multi-factor authentication (MFA) that strengthens access security by requiring two authentication factors to verify the identity of someone that wants access to an online service. A one-time password is a password of a specific length that is valid for only one login session. It is generated once, used once, and then it is discarded.

SSH, which stands for Secure Shell, is a network protocol that allows users to operate computers and servers over the Internet. It provides a secure channel over a very unsecured network. SSH uses encryption to ensure that the traffic between two connected devices can not be interpreted.

Emails are part of our daily routine and for many of us is the main tool of communication either for business, personal stuff, or both. Moreover, our email is our online identity, which is based on what we are and what we do on the web.