Not to be outdone by Facebook, Google is introducing an application sign-in via its Google Plus social network. “If you sign in to Gmail, YouTube or any other Google service, you can now use your existing credentials to sign in to apps outside of Google,” reads a Feb. 26 note on the Google Developers Blog. Despite Google’s strained relationship with Apple, the latter’s iOS platform is supported by Google Plus application sign-in, along with Android (obviously) and the Web. Google is emphasizing the security of its new add-on, claiming that protective measures such as two-factor authentication are baked into Google Plus Sign-In. When signing into an enabled Website with a Google ID, users can also install that Website’s mobile app to an Android device with a single click. Selective sharing is another feature. “Sometimes you want to share something with the world (like a high score), but other times you want to keep things to yourself (like fitness goals). With Google+ Sign-In and circles you decide who to share with, if at all,” read the blog posting. “In addition: Google+ doesn’t let apps spray “frictionless” updates all over the stream, so app activity will only appear when it’s relevant (like when you’re actually looking for it).” Obligatory Google swipe at Facebook functionality: check. When a user shares something from an app that relies on a Google Plus sign-in (such as a song or podcast), their friends will see an “interactive” post inside their own Google Plus stream, which they can click to access content or buy whatever’s been shared. Obligatory attempt to make Google Plus a “stickier” part of broader Web commerce: check. Developer material for the app sign-in can be found on Google’s Developers Website. While the ultra-connected Web is certainly convenient, a recent Facebook outage also hinted at the downsides of having single sign-ons and other unifying tools. On Feb. 7, users attempting to access CNN, Gawker, NBC News, The Huffington Post, and other popular Websites were redirected to a Facebook page reading, “An error occurred. Please try again later.” The downtime lasted for roughly an hour. “For a short period of time, there was a bug that redirected people logging in with Facebook from third party sites,” read the social network’s statement about the outage, widely circulated to news outlets. “The issue was quickly resolved and Login with Facebook is now working as usual.” While Facebook didn’t explain much more than that, analysts and pundits quickly pinned the blame on Facebook Connect, an API that allows users to login to Websites using their Facebook accounts. That’s certainly a convenience, but it’s also a vulnerability: if something goes wrong on Facebook’s end, there’s the possibility that huge swaths of the Web could go down. Like Facebook, Google Plus relies on interoperability with a variety of partners in order to operate in the most efficient manner possible. Google’s latest blog post makes it clear that the search engine giant’s engineers and developers are aware of the security and privacy issues inherent in that sort of ultra-connectivity.   Image: Google