That's again very likely a deja vu, your brain just mapped your real world to a memory of a dream.

They're pretty cool, if you read about them. Most of them are lattice based and working in thousands of dimensions.

The exceptions fall in the experimental area of encryption. What I mean by that is that the most applications you use today, WhatsApp, Signal, Banking apps, are all encrypted with a military grade encryption, but if you go try out experimental encrypting algorithms then you are at risk. Note that the latter does not happen in your regular day to day life, encryption standards are extremely uniform.

Edit: also, be aware that the applications that have implemented an unbreakable encryption algorithm can still decrypt your files as they have the keys to decrypt them. They're bound to not do it going by the privacy agreement but they potentially can. There are exceptions to it, like Apple's advanced E2E standard where not even Apple has your keys.

What do you think I'm talking about? CRT monitors?

Hardware alone cannot do a lot of stuff that we see today, the true power lies in silicon, and consequently the computation it does. Also, software is far from being 'too slow', I'd even go ahead and say that software at present is far more quicker than hardware.

More like,

!!!!! (Goes in)

iiiiii (Comes out)

No, you can not hear it, and that's because it's not being played into your ear, it's being laid on top of the sound that's coming into the audio device. There is no significant delay in it because there are fast dedicated chips in the sound devices that do a lot of computational work when it comes to sound waves. So, they're not always doing this in real time, sometimes they're predicting the sound before it's even completely addressed by the device. If there was a gunshot, far away, yes, it would mask it to a certain degree. That degree is what makes noise cancelling good or bad. There's a lot of other stuff that's done to facilitate the sound cancelling, one of them being plugging the ear completely so that no sound wave enter into the ear directly; no ear cavity is left unsealed. Watch THIS video and you'll be amazed to see how apparent this entire process is.

There's a lot that goes into noise cancelling, they are not always doing everything in real time. There are specially designed and fully dedicated chips on the sound devices that do just one thing, noise cancelling. They recognize certain sounds and apply the noise cancelling beforehand, thus eliminating that time window. They've been trained on millions of hours of noise and have gotten really good at what they do. Power of data, indeed.

In my opinion, bad noise cancelling is worse than no noise cancelling at all. Yes, when the noise cancelling isn't that good and responsive, there are moments of noticeable white noise. But with time, brands have gotten really good at noise cancelling and the manufacturers claiming to have noise cancelling in them do their job well.

Okay. Imagine a sound. A simple 'ting' from your phone. Sound travels in waves, you do know what waves look like, right? They're like recurring crests and troughs; up and down respectively. So, for the sake of this example, let's assume that the wave the sound 'ting' makes is one crest and one trough. One up and one down. What noise cancelling earphones do is create the opposite waves of that sound that just entered into them from your environment; which is 'ting' in this case. The earphones will recognize that the wave signature of this sound is one crest and one trough, so what it will do is create one trough and one crest (in that exact order), which are opposites of the 'ting' sound. Then it's going to place this newly created sound over the one that's coming from your phone. When you superimpose both of them together, you get a resultant zero and like that, you end up with noise cancellation.

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Edit: This explanation may seem a little vague, or I should say 'impractical'. If you're free, have some time, do watch this video to truly see this happening in real time.