2-Factor Authentication (2FA), sometimes referred to as two-factor verification, is a security method in which you provide **two different authentication factors** to identify yourself at login.
2-Factor Authentication (2FA), sometimes referred to as two-factor verification, is a security method in which you provide **two different authentication factors** to identify yourself at login.
This process is **performed to better protect** both your credentials and the resources that you can access.
This process is **performed to better protect** both your credentials and the resources that you can access.
In the **first login step**, you start with the usual entry of a good password. The service then confirms the correctness of the password entered.
In the **first login step**, you start with the usual entry of a good password. The service then confirms the correctness of the password entered.
This does not, however, lead directly to the desired entrance - but to a further barrier.
This does not, however, lead directly to the desired entrance - but to a further barrier.
The **second login step** prevents unauthorized third parties from gaining access to your account just because they might have stolen your password.
The **second login step** prevents unauthorized third parties from gaining access to your account just because they might have stolen your password.
A quite common 2nd-factor is a time-based one-time **confirmation code** generated by a **2fa-generator app** you installs and initializes once on one of your personal devices.
A quite common 2nd-factor is a time-based one-time **confirmation code** generated by a **2fa-generator app** you installs and initializes once on one of your personal devices.
This 2fa-generator app then provides (in our case every 30 seconds) a new confirmation code that needs to be entered on the login page.
This 2fa-generator app then provides (in our case every 30 seconds) a new confirmation code that needs to be entered on the login page.
These two factors for authentication combine the building blocks **knowledge** and **possession** in the login procedure.
These two factors for authentication combine the building blocks **knowledge** and **possession** in the login procedure.
-**knowledge** - the secret knowledge is the password you enter.
-**knowledge** - the secret knowledge is the password you enter.
-**possession** - With the confirmation code you show that you are in possession of a certain device (e.g. your smartphone), because only the *2fa-generator app*, installed on that device, can generate the necessary *confirmation code*.
-**possession** - With the confirmation code you show that you are in possession of a certain device (e.g. your smartphone), because only the *2fa-generator app*, installed on that device, can generate the necessary *confirmation code*.
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<p style="float:right">Source: Bundesamt für Sicherheit in der Informationstechnik</p>
<p style="float:right">Source: Bundesamt für Sicherheit in der Informationstechnik</p>
The **2fa-generator app** calculates the current personal **confirmation code** completely autonomously from the outside world using a standardized and open algorithm for the generation of **Time-based One-Time Passwords (TOTP)**.
The **2fa-generator app** calculates the current personal **confirmation code** completely autonomously from the outside world using a standardized and open algorithm for the generation of **Time-based One-Time Passwords (TOTP)**.
The TOTP algorithm was published in 2011 by the [Internet Engineering Task Force (IETF)](https://www.ietf.com) as [RFC 6238](https://tools.ietf.org/html/rfc6238). The TOTP algorithm is a hash function in which a secret code is hashed together with the current time.
The TOTP algorithm was published in 2011 by the [Internet Engineering Task Force (IETF)](https://www.ietf.com) as [RFC 6238](https://tools.ietf.org/html/rfc6238). The TOTP algorithm is a hash function in which a secret code is hashed together with the current time.
Behind the hash function is the HMAC-based One-time Password Algorithm according to [RFC 4226](https://tools.ietf.org/html/rfc4226) - in simple terms nothing more than a standard that forms a hash in a certain way.
Behind the hash function is the HMAC-based One-time Password Algorithm according to [RFC 4226](https://tools.ietf.org/html/rfc4226) - in simple terms nothing more than a standard that forms a hash in a certain way.
The calculation includes both a **"secret initialization code"**, that is known to both the server and the client, and the **current time**.
The calculation includes both a **"secret initialization code"**, that is known to both the server and the client, and the **current time**.
The final one-time *confirmation code* is generated from these two inputs and is valid for a certain period of time. (in our case for **30 seconds**).
The final one-time *confirmation code* is generated from these two inputs and is valid for a certain period of time. (in our case for **30 seconds**).
The procedure can be implemented in such a way that slight differences in time between client and server are accepted.
The procedure can be implemented in such a way that slight differences in time between client and server are accepted.
Hence, any confirmation code is time-based, calculated locally, and always unique.
Hence, any confirmation code is time-based, calculated locally, and always unique.
The TOTP algorithm can also be implemented in hardware as a so-called "hardware token" (e.g. [Protectimus Tokens](https://www.protectimus.com/tokens/))
The TOTP algorithm can also be implemented in hardware as a so-called "hardware token" (e.g. [Protectimus Tokens](https://www.protectimus.com/tokens/))
Before you can use 2FA for Jupyter-JSC a random, user-specific, unique and **secret initialization code** must be known by both Jupyter-JSC and the users 2fa-generator app.
Before you can use 2FA for Jupyter-JSC a random, user-specific, unique and **secret initialization code** must be known by both Jupyter-JSC and the users 2fa-generator app.
This *secret initialization code* gets generated by Jupyter-JSC and is shown as a **QR-Code** (or string) on the activation page.
This *secret initialization code* gets generated by Jupyter-JSC and is shown as a **QR-Code** (or string) on the activation page.
The QR-Code provides the *secret initialization code* with the descriptive data (1) algorithm = TOTP, (2) period of validity = 30s.
The QR-Code provides the *secret initialization code* with the descriptive data (1) algorithm = TOTP, (2) period of validity = 30s.
Please ensure you set these descriptive dates manually in your 2fa-generator app **if you prefer to use the string** instead of the QR-Code.
Please ensure you set these descriptive dates manually in your 2fa-generator app **if you prefer to use the string** instead of the QR-Code.
Next, the 2fa-generates app provides now a **verification code** you have to enter on the activation webpage.
Next, the 2fa-generates app provides now a **verification code** you have to enter on the activation webpage.
Jupyter-JSC now compares the *verification code* you provide with the one generated by Jupyter-JSC.
Jupyter-JSC now compares the *verification code* you provide with the one generated by Jupyter-JSC.
