Google Authenticator: Difference between revisions

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Google Authenticator is an open-source software based two-step authentication token developed by Google. The Authenticator provides a six digit number users must provide in addition to their username and password to log in to Google services. The Authenticator can also generate codes for third party applications, such as LastPass or Dropbox.

Implementation

Google provides iOS,^[1] BlackBerry and Android^[2] versions of Authenticator. Several third party implementations are available.

Windows Phone 7: Authenticator
Windows Mobile: Google Authenticator for Windows Mobile
Java CLI: Authenticator.jar
Java GUI: JAuth
J2ME: gauthj2me lwuitgauthj2me totp-me MOTP Mobile-OTP (chinese only)
PalmOS: gauthj2me
Ruby: google_authenticator_auth gem (third party implementation)
webOS: GAuth
Windows: gauth4win
HTML5: html5-google-authenticator
MeeGo/Harmattan (Nokia N9): GAuth

Technical description

Google generates an 80-bit secret key for each user. This is provided as a 16 character base32 string or as a QR code. The client creates a HMAC-SHA1 using this secret key, with the message being the number of 30 second periods having elapsed since the Unix epoch. A portion of the HMAC is extracted and converted to a 6 digit code.

Pseudocode

 function GoogleAuthenticatorCode(string secret)
     key := base32decode(secret)
     message := current Unix time ÷ 30
     hash := HMAC-SHA1(key, message)
     offset := last nibble of hash
     truncatedHash := hash[offset..offset+3]  //4 bytes starting at the offset
     Set the first bit of truncatedHash to zero  //remove the most significant bit 
     code := truncatedHash mod 1000000
     pad code with 0 until length of code is 6
     return code

Technology

Google Authenticator implements the time-based One-time Password Algorithm as defined in IETF RFC 6238, and the HMAC-based One Time Password Algorithm as defined in IETF RFC 4226.

Usage

Google Authenticator can be used for the following websites:

References

External links

Google Authenticator on Google Help
Google Authenticator open source project on Google Code
Google Authenticator implementation in Python on Stack Overflow

[1] OS version of Google Authenticator

[2] Android version of Google Authenticator

[1]

@@ Line 40: / Line 40: @@
 ==Usage==
 Google Authenticator can be used for the following websites:
+* [[Dropbox (service)|Dropbox]]
-* DropBox (currently beta - rolling out to more and more accounts)
 * [[Gaia Online]]
 * Google Mail
 * Google Apps
 * LastPass
 * WordPress (Plugin is needed)
+* [[Drupal]] ([http://drupal.org/project/ga_login Plugin] is needed)
 * [https://mtgox.com/ Mt.Gox] [[Bitcoin]] exchange
 * [https://blockchain.info/wallet/ Blockchain.info] [[Bitcoin]] wallet