Why does the Google Authenticator app have "obsolete" in its title on Play Store?
Does it work? Can I still use it for two-factor authentication? Is there a preferred method?
Looks like Google has released a new version of Authenticator (as of March 21, 2012) under a new package name:
Different package names means that you can have them both installed simultaneously, but my guess is that Google will eventually remove the old version from the Play Store.
Installing Authenticator 2 without uninstalling Authenticator allows Authenticator 2 to import your currently configured sites.
I've read a few posts from people claiming that Google lost their signing key, and this why they have to release a new app under a new package name. I want to emphasize that there is no evidence to support this claim. While it is true that signing keys cannot be changed with app updates and therefore require a completely new app/package name, a more plausible explanation could be that Google wants to integrate Authenticator more tightly (e.g., shared UIDs, signature permissions) with other apps (see below).
Additional info for those interested:
The signing key used on the old version of Google Authenticator (SHA1 fingerprint:
24:BB:24:C0:5E:47:E0:AE:FA:68:A5:8A:76:61:79:D9:B6:13:A6:00) is also used to sign: Scoreboard, Goggles, Finance, Google Voice, Shopper, Transalte, Chrometophone, Earth, Reader, and a few others.
The signing key used on the new version of Google Authenticator (SHA1 fingerprint:
38:91:8A:45:3D:07:19:93:54:F8:B1:9A:F0:5E:C6:56:2C:ED:57:88) is used to sign: Google Maps, Google Play Store, Gmail, Google+, Google Chrome and Google Music.
Update: Google has put up a blog post talking about the new up as well as the upgrade procedure.