Re:Zoom rolled their own encryption scheme, transmit keys th...
by sdenton4 on Friday April 03, 2020 @09:50PM
(#22775551)
For audio, you don't want to send a wav file over the line, as it's incredibly wasteful. Once it's reasonably encoded, you necessarily end up with a lower entropy steam... So should still have some version of "solid blocks of color", especially for silence. (Exact details depend on the codec, though.)
Re:Zoom rolled their own encryption scheme, transmit keys th...
by barrkel on Friday April 03, 2020 @10:06PM
(#22775611)
Lossy compression reduces entropy, I'd expect fewer repeats and more of what looks like random data in any compression worth its salt. Thomas also mentioned AAC, not PCM. I agree on the silence, but it would come up as smaller packets, not repeated packets, IMO. And then we're back to timing analysis of speech.
Re:Zoom rolled their own encryption scheme, transmit keys th...
by killjoywashere on Friday April 03, 2020 @10:54PM
(#22775846)
> Lossy compression reduces entropy, I'd expect fewer repeats and more of what looks like random data in any compression worth its salt.
Um, so, just to make sure I understand you, you're implying that lossy compression is not worth its salt? Because you will surely have more repeats in a lower entropy space.
Re:Zoom rolled their own encryption scheme, transmit keys th...
by tptacek on Saturday April 04, 2020 @12:06AM
(#22776128)
You get essentially no repeats (collisions, more precisely) in the AAC streams I played with. Some block boundary headers; that's it.
The trick with ECB is that you're relying on 128-bit blocks of plaintext repeating with perfect alignment, and, to do anything useful with it, those repeats leaking useful information. In a bitmap image of a penguin, those repeats are easy: they're blocks of pixels of uniform color, and all ECB is doing is permuting their colors. That's less intuitively true of audio (where I'm not really seeing repeats at all, but, again, you should just play with it).