Re: [TLS] TLS 1.3 - Support for compression to be removed

[Tony Arcieri <[e-mail]>]

On Sun, Oct 4, 2015 at 11:50 AM, Dave Garrett <[e-mail]>
wrote:

> I can think of a way to do this, but the people who want compression badly
> probably won't like it due to the need to pad heavily.
>
> 1) Pick a fixed bandwidth
> 2) Compress & encrypt the stream
> 3) Send the compressed stream at a rate blocked to the cap
> 4) Whenever below the cap, pad the stream to the cap
>
> Maintain a fixed transmission of data per unit time and there's no way to
> tell the size of anything (even if delivery doesn't match the rate).


This sounds like Constant Bitrate (CBR) compression, which works for
encrypted media (e.g. encrypted voice and video), but probably isn't
particularly useful outside the realm of realtime media. It was a solution
that seems to work for attacks that could e.g. transcribe encrypted phone
calls by studying patterns in Variable Bitrate (VBR) compression on speech.

Typically compression is used to lower the overall size of data, working on
a wide class of inputs. In the perceptual coding case the class of inputs
is constrained, and the goal is to keep the data rate constant, not
optimally small.

-- 
Tony Arcieri