|
I actually work on quantum computation, and let me say that ISPs are not going to be using quantum computers to do real time decrpytion of internet traffic in at least the next 20 years.
As for guessing the contents of files:
Encrypted files are not really like pictures. A *unencrypted* picture has a recognizable patterns in it. You can encrypt a picture as well. An *encrypted* picture if viewed would look like a random collection of pixels, something like the "snow" you used to see on TV screens (though in full color).
Basically what encryption does is "randomize" the patterns in a file. It does this in a way that is very hard (though not impossible) to "un-randomize".
|