Does anyone know how the Apple Watch unlock feature work in macOS Sierra?

I figured out, that I have to be very near my Mac, that the feature works.

Does it use Bluetooth (BLE) or WIFI?

It would be really nice to get some details about this nice feature.


It uses both Bluetooth LE 4.0 AND 802.11ac WiFi.

Bluetooth is used to discover the Apple Watch and establish a connection.

Then it uses WiFi to do "time-in-flight" calculations - i.e. to figure out how far your watch is from the Mac. The Mac needs to support 802.11ac WiFi for this to work. All watches are supported, both the old and the new - even though the old ones does not support 802.11ac.

This way it is possible to prevent attacks such as someone planting a "bluetooth repeater" near you, so that it could replay your bluetooth responses captured this way to a Mac located somewhere remotely.

  • The timing packets are likely encrypted as well or at least the time stamps are encrypted to prevent playback attacks where someone captures the traffic that unlocked the Mac today at 8 am and then tries to replay it tomorrow when you and your watch are not present. – bmike Oct 4 '16 at 11:11
  • The first-generation Apple Watch does not have 802.11ac. – At0mic Oct 4 '16 at 12:23
  • Does apple provide any official docs? – patrickS Oct 4 '16 at 12:49
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    You can hear Phil Schiller/Craigh Federighi explain the implementation here: vimeo.com/171186055#t=40m15s – jksoegaard Oct 4 '16 at 13:07
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    Also a nice article: networkingnerd.net/2016/09/21/… – patrickS Oct 21 '16 at 5:59

I found a interesting article, where this feature is described in detail:



It uses both Bluetooth and WIFI.

Bluetooth determines the distance between your Mac and AppleWatch , WIFI checks if your connected to the same network to 'grant you access'.

Think of Bluetooth Beacons, they only work if your near ~ cm from a beacon. You can setup beacons to show up on your device if your close enough. The Mac works like a beacon this way.


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