I'm not entirely sure if this is something you're looking for, but this is what I've got working on my Galaxy S3.
I can use my NFC ring to bypass my standard Android lockscreen security AND scan through the NFC Unlock app prompt. However, if I don't use my ring, I can still unlock my phone using a standard lockscreen PIN and the PIN I set up in the NFC Unlock App.
I have the standard lockscreen PIN set to a 6 digit code. I have a 4 digit PIN set in the NFC Unlock App. Normally with just this in order to unlock my phone I would have to enter my 6 digit PIN on the lockscreen and then scan my NFC ring. With my new procedure I only have to scan my NFC ring once and it immediately unlocks my device.
Things you need:
- Rooted Android
- Standard lockscreen security (PIN, pattern, password)
- Secure Settiings
- NFC Unlock App
- A Tasker Project file to import, called NFC Key
The Tasker Project file you require is available on XDA, which is available here.
Here are the steps I took:
- Setup your standard lockscreen security. This can be pattern, PIN or password.
- Install and setup the NFC Unlock app. Make sure it's working normally. Make sure that the unlock procedure kicks in after your standard lockscreen security has cleared. For example, if you have a pattern set, then clearing the pattern should automatically bring up the NFC Unlock prompt.
- Install and setup Tasker
- Install and setup Secure Settings. You'll need to install the Helper/Compatibility module. Also make sure to make Secure Settings as a Device Administrator in the systems Settings app.
- Download and extract the NFC Key file (it's an XML) to somewhere on your internal storage, e.g. /sdcard0/Tasker/projects
- Open up Tasker and import the XML you just copied to your device. Make sure that you've disabled Beginner Mode in the Preferences. Tap on the "Home" icon at the bottom of the interface, select "Import". Navigate to the location you copied the XML to and select it. It'll warn you to check the settings before you commit them, go ahead if you like, otherwise just save the settings.
- Beside the "Home" icon in Tasker you should see a tab called "NFC Key". Selecting it will show 4 Tasks and 1 Profile.
- Exit Tasker, then turn your device off.
- Turn your device on, make sure the lockscreen is showing, then tap your ring.
If all worked out, your phone should automatically scan in past your lockscreen security AND the NFC Unlock prompt. If you watch carefully, you'll actually see the NFC Unlock prompt show up briefly before clearing out.
What this Tasker Project does is recognize a NFC tag (any NFC) and bypasses the standard lockscreen security bys disabling it and then re-enabling it. Once it's past the standard lockscreen security, the NFC Unlock app prompt will show up and since you're already scanning in your NFC ring it will immediately pick up your stored NFC tag key and unlock the final gate.
The reason why I consider this to be pretty secure is because even if someone manages to scan in any random NFC tag to bypass your standard Android lockscreen, you still need to get through the NFC Unlock app's own security prompt. So they'll still need your NFC ring or your registered PIN or Google Account in order to actually get into your phone. So ultimately this really only bypasses one of two security gates. Even if you lost your ring you can still get into your device the normal way.
Hopefully this helps anyone else with an Android device who wants a pseudo 2 factor authentication method!