Saturday, July 30, 2022

The private life of a privacy screen

Let's say you have a laptop which you take to libraries, coffee places, and other public locations to get fresh air and inspiration while you write away a new article or piece of code. How do you keep what you are doing to yourself?

You on the corner who said "VPN" (when you think aloud, you do think aloud), you are right. That helps with the network connection. But what about keeping the prying and curious eyes off other customers of the same establishment you are in? Yes, this time the answer is the privacy screen, which has not only been around for decades but also is the name of this post.

How good is a privacy screen

Some are really useless. I remember when I was in college one that was so bad the person using the computer could barely see what she was doing. It was just a step above bolting a steel plate to the front of the monitor; I guess if you the user cannot see what you are done, the same happens to the potential attacker, who then has to rely on keylogging and scanning the screen contents using software.

Others work well enough to be useful within some limitations. Case in point is the one I will be test driving today. It's brand is... well, I have no idea. I found it besides the trash can in an office once. It is one of the common polarized ones and had no scratches nor too many fingerprints on its surface. As it was larger than the (old) laptop monitor I wanted to use, I grabbed it. And then cut it to size and secured it using Scotch tape (I am calling the brand out here because that is the roll I have).

It is one of those garden-variety polazided screens, which blocks the light if you move too far from being perpendicular to it. How far must you move from looking straight at it before the privacy part of the privacy screen is "engaged"? It depends on the make. Let see how it works by simulating the kind of situation that can happen anywhere.

  • Here is a picture of it installed in the test laptop, which is currently setup to replicate that of Mort Villanous, an aspiring supervillain who is in some public library writing his current world domination plot. In fact, this would be the point of view of our evildoer in-the-making. Note the tape on the corners of the privacy screen.

    From his point of view, he can clearly see the screen and, as a result, work on his important and secret document. The eagle-eyed members of the audience may have seen my exclusive and expensive camera cover; I will try to provide a link to it later on. But if you have to ask how much, you can't afford it.

  • Next let's pretend we are the Tom Goodfellow, secret agent tasked to observe what villanous things our villanous villain, Villanous, is up to. Wearing his trademark 30 gallon white hat, chaps, and 7 Gold Chains or Virtue, he discretely approaches Mort from the right, this is what Tom sees.
    From his current point of view, the laptop looks as if it is turned off, as the surrounding background is reflected on its back screen. That won't do.
  • Knowing Mort has not noticed him yet, Tom heroically slides a bit closer to the aspiring villain. This time the privacy screen proves no match to the hero's eyes, as at this angle it exposes a hint of an evil deed in the making, namely a document is open and being worked on: he can see there are words written using different font sizes, but he still can't read them. These clues tell Tom he is dealing with a polarized privacy screen!
  • Embolded with confidence and knowledge of how this kind of screen works, our hero inches even closer to the villain. And he is rewarded with being able to finally begin read the contents of the document!
    Unfortunately, the secret agent made the typical hero's mistake. Being a bit myoptic, he leaned too much towards the computer. As a result Mort Villanous not only heard the gently clanking of the secret agent's gold chain as it touched the table, but also felt it crushing his arm. Aware now of the presence of his enemy, Mort immediately closed the laptop, shouted "do you mind?" ignoring proper library ethiquette, and walked away.

Moral of the Story

Whether you are plotting to rule the world, or just trying to read email in peace at a public location, getting a privacy screen is not a bad idea. However, test it first to see how large is its "non-private" region so you can plan where you will be seating and what will be behind you.