

Ask HN: How does Knock to unlock work? - skycocker

It&#x27;s been bothering me for a few weeks now: how does Knock to unlock app work on the OS X side?<p>I read about authorization plugins like this NameAndPassword example: https:&#x2F;&#x2F;developer.apple.com&#x2F;library&#x2F;mac&#x2F;samplecode&#x2F;NameAndPassword&#x2F;Introduction&#x2F;Intro.html<p>After I managed to build and install it (which wasn&#x27;t so easy: http:&#x2F;&#x2F;stackoverflow.com&#x2F;questions&#x2F;21582995&#x2F;custom-login-lock-screen-in-os-x-mavericks) it won&#x27;t log me in (more discussion here: http:&#x2F;&#x2F;stackoverflow.com&#x2F;questions&#x2F;21056322&#x2F;customize-login-screen-mac-osx-sfauthorizationpluginview#comment33224960_21056322). With this happening and the documentation with examples being outdated, I think it&#x27;s not the proper way to modify the lock screen today. Also, I guess it only works on the login&#x2F;fast-user-switch screen, but not on the wake from sleep one. So basically my question is: how <i>exactly</i> does Knock modify the lock screen, and how is it possible to recreate this behavior with some other plugin? (I&#x27;m currently working on something like fingerprint scanner)<p>One user on SO wrote about some login agents: http:&#x2F;&#x2F;stackoverflow.com&#x2F;a&#x2F;21835312&#x2F;2113110 - I&#x27;ve tried pre login agents, but I guess it&#x27;s not the same thing.
======
Jonovono
You are curious about something different than I was about Knock to unlock. I
was wondering how they detect the knocking and not get false positives. I
started working on a project that recognises knocks/taps (just incase anyone
else comes here and is curious about this part!)
[https://github.com/Jonovono/Tapadoodledo](https://github.com/Jonovono/Tapadoodledo)

