Windows Enterprise Desktop

Feb 24 2017   10:38AM GMT

Win10 Dynamic Lock Gets Cool Tool

Ed Tittel Ed Tittel Profile: Ed Tittel

Tags:
Bluetooth Devices
smartphone
Windows 10
Windows Security

Almost two weeks ago, I blogged here about the addition of a new security feature in Insider Preview Build 15031. It’s called Dynamic Lock. Dynamic Lock senses the signal strength from a cellphone paired via Bluetooth with a Windows 10 device. When that signal drops below a threshold, the feature causes the Win10 device to lock itself. This turns off direct access, and puts up the lockscreen, much like an inactivity disconnect. Now, thanks to the efforts of Rafael Rivera at Thurrott.com/Petri.Net, Win10 Dynamic Lock gets cool tool power. It comes in the form of a small utility named draconyx.exe. Here’s a screen cap:

Win10 Dynamic Lock Gets Cool Tool

The draconyx.exe program measures signal strength from Bluetooth devices once every minute or so and reports current readings.

When Win10 Dynamic Lock Gets Cool Tool, What Can It Do for You?

Internally, Dynamic Lock uses a measure of something called Received Signal Strength Indication (RSSI) to make the call on locking a device. According to Rivera, the control connects to a Bluetooth-paired cellphone “several times a minute.” Each time it does, it measures the RSSI value, then disconnects from the phone. When that value drops below a certain level, it locks the device. Rivera’s observation about the way this works is worth heeding, for those running phones and Win10 devices from battery: “Because an active connection is established every time this ritual is performed, you can bet there will be a battery life hit on both devices.” You’ve been warned!

That threshold value, according to Rivera, appears to be about -10 deciBels (dB). For Bluetooth devices 0 dB represents an optimal signal. A drop of 10 dB represents almost 70% reduction in signal strength, according to a deciBel to amplitude converter. That’s a pretty major drop and may be further away than it really needs to be before imposing a lock. At home, I was able to observe the lock kick in when I carried the phone all the way to the other side of the house, about 45 feet away. Perhaps that’s because my signal-rich kitchen sits between the room where the Dell Venue Pro 11 lay and the other room where I put the paired iPhone.

Using Draconyx.exe to Set the Lock Threshold

For those who want to lower the default distance, Rivera identifies a registry value BluetoothRssiMaxDelta (DWORD) one can set up to tweak the threshold. (See his story for the details.) You can use it to set up a threshold to lock your device when you leave the room, your office space, or your building, as you like. And that’s what makes it a cool tool. Thanks Rafael: Nice work!

Rivera also opines that the Dynamic Lock is flaky enough that it might not make it into the upcoming Creators Update in April. We’ll have to wait and see on that, but I hope it stays in the production OS. It’s an interesting and convenient feature, as far as I can tell.

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