How does Google Authenticator work? (Part 3)

Part 3 is the last part in this short cycle. Here I’ll explain all the details around Time-based One-Time Password algorithm. I’ll finish up by also elaborating on things common to both, HMAC-Based One-Time Password algorithm: QR Codes used to easily transfer secrets from the server to the Authenticator app Base32 algorithm – used to store non-printable secret in a URI (effectively stored by the QR Codes mentioned above). TOTP One way to avoid the problems with lack of feedback between server and the app would be to shift from using a counter that is increasing with every authentication attempt to a counter based on, for example, a time stamp. [Read More]

How does Google Authenticator work? (Part 1)

When you’re accessing services over the WEB – let’s pick GMail as an example – couple of things have to happen upfront: The server you’re connecting to (GMail in our example) has to get to know who you are. Only after getting to know who you are it’s able to decide what resources you are allowed to access (e.g. your own email inbox, your Calendar, Drive etc.). Step 1 above is called authentication. [Read More]