Knock starts off as this really cool idea: that a Mac that supports Bluetooth 4.0 (2011 or later models, mostly) could connect with an iPhone app running over Bluetooth low-energy, and that iPhone could be used instead of the password on the Mac once both the iPhone and Mac apps are set up. Just knock twice on the phone, tapping with multiple knuckles, whether the iPhone’s screen is turned on or not, and it enters the password on the Mac to unlock it. It works exactly as it’s described.
I just don’t know if it’s worth it, though.
It starts with the whole Bluetooth thing. The developers claim repeatedly that using Knock doesn’t affect battery life. But having Bluetooth enabled on an iOS device in my experience has been a one-way ticket to increased battery drain. So maybe just having the radio on in a low-energy mode device won’t be a huge drain, but it keeps me very paranoid. Maybe it was having Blocky Roads still open when I locked my device that caused my battery to drain 20% over two hours, and not Knock, but it sure made me feel paranoid. Basically, Knock asks me to throw away years of expectations to use it, and it would take a long time to trust that it wasn’t actually draining my battery faster than everything else that does.
And what’s this all for, anyway? The opportunity to save a few seconds by knocking on my iPhone instead of typing in a password? It’s really not that much more convenient. Perhaps for those who have long and heavily-hashed passwords, then they might save some time and effort instead of having to remember an unmemorable password. But they probably wouldn’t trust Knock anyway, even if it does claim to use 2048-bit encryption to store the password and to make sure that it’s actually communicating with the Mac it’s set up to communicate with. It can’t serve as a nifty remote way to wake up a Mac from sleep since the Bluetooth disconnects while the Mac goes to sleep. The developers claim in their FAQ that they may just have a solution in an upcoming update. For most people it’ll just be kind of limited. It’s not that much more difficult to type in the average password.
So, yes, Knock is pretty neat. But it’s a novelty.
