Google Authenticator

File:Google Authenticator for Android icon.svg

The app is first installed on a smartphone to use Authenticator. It must be set up for each site with which it is to be used: the site provides a shared secret key to the user over a secure channel, to be stored in the Authenticator app. This secret key will be used for all future logins to the site.

To log into a site or service that uses two-factor authentication and supports Authenticator, the user provides a username and password to the site. The site then computes (but does not display) the required six- to eight-digit one-time password and asks the user to enter it. The user runs the Authenticator app, which independently computes and displays the same password, which the user types in, authenticating their identity.{{Citation needed|date=June 2016}}

With this kind of two-factor authentication, mere knowledge of username and password is insufficient to break into a user's account - the attacker also needs knowledge of the shared secret key or physical access to the device running the Authenticator app. An alternative route of attack is a man-in-the-middle attack: if the device used for the login process is compromised by malware, the credentials and one-time password can be intercepted by the malware, which then can initiate its login session to the site, or monitor and modify the communication between the user and the site.{{Cite web|first1=Jovi|last1=Umawing|date=6 January 2022|title=Intercepting 2FA: Over 1200 man-in-the-middle phishing toolkits detected|url=https://www.malwarebytes.com/blog/news/2022/01/intercepting-2fa-over-1200-man-in-the-middle-phishing-toolkits-detected|access-date=27 April 2023|website=www.malwarebytes.com|language=en-US}}

• {{Cite web|first1=Neko|last1=Papez|date=25 April 2023|title=The art of MFA Bypass: How attackers regularly beat two-factor authentication |url=https://www.menlosecurity.com/blog/the-art-of-mfa-bypass-how-attackers-regularly-beat-two-factor-authentication/|access-date=27 April 2023|website=menlosecurity.com|language=en-US}}

During setup, the service provider generates an 80-bit secret key for each user (whereas RFC 4226 §4 requires 128 bits and recommends 160 bits).{{cite journal|url=https://tools.ietf.org/html/rfc4226#section-4 |title=RFC 4226 - HOTP: An HMAC-Based One-Time Password Algorithm |publisher=Tools.ietf.org |date=2005-02-15 |doi=10.17487/RFC4226 |access-date=2019-03-25|last1=m'Raihi |first1=D. |last2=Bellare |first2=M. |last3=Hoornaert |first3=F. |last4=Naccache |first4=D. |last5=Ranen |first5=O. |url-access=subscription }} This is transferred to the Authenticator app as a 16, 26, or 32-character base32 string, or as a QR code.

Subsequently, when the user opens the Authenticator app, it calculates an HMAC-SHA1 hash value using this secret key. The message can be:

• The number of 30-second periods since the Unix epoch (TOTP) as 64-bit big endian integer; or
• A counter that is incremented with each new code (HOTP).

A portion of the HMAC is extracted and displayed to the user as a six- to eight-digit code; The last nibble (4 bits) of the result is used as a pointer, to a 32-bit integer, in the result byte array, and masks out the 31st bit.

The Google Authenticator app for Android was originally open source, but later became proprietary. Google made earlier source for their Authenticator app available on its GitHub repository; the associated development page stated:

"This open source project allows you to download the code that powered version 2.21 of the application. Subsequent versions contain Google-specific workflows that are not part of the project."{{cite web|url=https://code.google.com/p/google-authenticator/|title=google-authenticator - Two-step verification - Google Project Hosting|date=18 May 2022 }}

The latest open-source release was in 2020.

• Multi-factor authentication
• HMAC-based one-time password
• FreeOTP
• LinOTP
• Comparison of OTP applications

{{reflist|colwidth=30em}}

• [https://support.google.com/accounts/answer/1066447 Google Authenticator] on Google Help
• [https://github.com/google/google-authenticator-android Google Authenticator (Android)] and [https://github.com/google/google-authenticator Google Authenticator (other)] legacy source code on GitHub
• [https://github.com/google/google-authenticator-libpam Google Authenticator PAM module] source code on GitHub
• [https://stackoverflow.com/questions/8529265/google-authenticator-implementation-in-python Google Authenticator implementation in Python] on Stack Overflow
• [https://github.com/MicroPyramid/django-mfa/ Django-MFA Implementation Using Google Authenticator] - Django-MFA is a simple package to add an extra layer of security to your Django web application. It gives your web app a randomly changing password as extra protection.
• [https://github.com/google/google-authenticator Source code of version 1.02] on GitHub

{{Google LLC}}

Category:Authentication

Authenticator

Category:Internet properties established in 2010