In August of 2015, the WSJ posted an article about a Japanese researcher who will sell you special sunglasses that will protect you from biometric face recognition for $240. I worked with privacy researcher Andy Greenberg on an article about this a while back. You really don't need special $240 sunglasses. Large, dark sunglasses will do.

There isn't a lot of detail on how these special sunglasses work, but we can make some educated guesses. They mention that it "prevents the recognition systems in digital cameras and smartphones from spotting a human face". That's a good place to start.

In biometric face recognition, there are two components - face finding and face matching. First you have to find a face in a scene, and then once you have extracted that face you can try to match it to something. Obviously if you can't find the face then you can't match it. Adam Harvey created a neat visualization of how the face finding process works, which you can see in the video. Basically, the algorithms look for the characteristics of a face in a manner not dissimilar to how humans do it - they look for an oval-ish shape with two eyes, a nose, a mouth, etc. That's why they sometimes see faces in things that aren't faces (just like humans do).

However, the algorithm doesn't literally look for faces. That's not how biometrics work and it has no idea what a face is. Computers are really stupid that way. Instead, it is looking for an object that matches what it is trained to find - in this case faces. It doesn't have to look for faces with eyes. It can look for faces with sunglasses, and many modern face-finding algorithms find faces with sunglasses just fine. I suspect it would not be hard to train an algorithm to find faces with these special sunglasses as well. In fact, an algorithm could be trained to find faces with these specific sunglasses, which is especially interesting because wearing these sunglasses means someone is trying to hide.

Once you find a face by normal means or by special tricks, matching is relatively easy. There is plenty of information left in the face outside of the eyes to make a match.

If you want to buy these glasses to be trendy and cool, go for it. And it will protect you from face matching until they become popular enough to be noticed by biometric researchers. But in the long run, they really won't help you at all. What will help, you though, is the computational complexity of large-scale biometric matching. It really isn't as feasible now as people think.

NOTE: This is a reprint of an article originally published by Alex Kilpatrick in August 2015 on a different blog. We are reposting them on the Blink Identity blog because these issues are important and we want to keep our writing on these issues in one place.