Is Knock secure?
Yes. Knock doesn't replace your password, and Knock doesn't modify or replace any of your Mac's built in security features. During pairing, your Mac generates a 1024-bit RSA key pair and sends the public key to your iPhone via Bluetooth LE. It also generates a 256-bit AES private key. Your password is then encrypted on your Mac using the AES key, and the encrypted result is transmitted via Bluetooth LE to your iPhone and stored there on the iPhone’s keychain. The AES private key for your password is stored on your Mac. It never leaves the Mac.
The RSA public key is used to encrypt all Bluetooth communication from the iPhone to the Mac. Hence, your password is doubly protected – once with 256-bit AES encryption and again with 1024-bit RSA encryption.
What if someone steals my iPhone?
If for any reason you can't Knock to unlock your Mac, you can still sign in with your old-fashioned password. If your iPhone is lost or stolen, simply sign in with your password and disable it with one click.
Is Knock's connection to my Mac encrypted?
Yep, Knock uses 1024-bit RSA encryption.
What if someone steals both my iPhone and my Mac?
Yikes, talk about a rough day. Even in the case that a thief makes off with both your iPhone and your Mac and is aware that your Mac has Knock installed, you can easily and quickly wipe your iPhone using iCloud to prevent the thief from gaining access to your Mac. (You'll want to do that anyway, even if you don't use Knock.)
What if my iPhone is locked with a passcode or TouchID?
Knocking on your iPhone will unlock your Mac even if your iPhone is locked.
If you require extra security, you can enable Touch to Unlock. Instead of knocking on your iPhone you’ll swipe a notification and use TouchID (or Pin) to unlock your Mac.
Can Knock be fooled into giving my password to a malicious application?
No. Knock verifies the unique code signature of your Mac's login system to make sure only it can access your password.
What if someone near me is also using Knock?
No worries. Your Mac only recognizes your Knock.
Does Knock use its own fake, proprietary lock screen?
No. Knock uses Apple's built-in OS X lock screen with our UI on top.
Why is Knock requesting access to external sites like Facebook.com and Twitter.com?
Our setup process loads a web view for http://www.knocktounlock.com/share.html, which includes share buttons that call external APIs.