[messaging] Audible public-key fingerprints

[Mansour Moufid]

On Wed, 20 Aug 2014 06:09:24 +0200
Arne Renkema-Padmos <renkema.padmos at gmail.com> wrote:

> As an alternative to audible communication you could also try
> ultrasound, but I'm not sure how well that works quality wise.
> Regarding end-user agency in determining when their device broadcasts
> their signal: if you don't want broadcasting to happen all the time
> (very understandable), then you probably want some kind of explicit
> action from the user (tap button, gesture, wiggle phone in a certain
> way, etc), or some implicit action (e.g. wearables that detect the
> performing of a handshake: http://zenodo.org/record/11163).
> 
> As already noted, the "fun" factor might also play a role in going for
> audible fingerprints, but how do you keep it fun the 20th time that
> you're pairing devices?

Ultrasound is a good idea. I imagine the audible frequencies are good
for short exchanges like keys, and ultrasound for something longer like
a conversation. The software to do both is essentially the same.

With a good enough microphone and speakers that sample/emit at 48 kHz,
the 4 kHz band above 20 kHz is inaudible, so it can be used in the
background without getting annoying.

Mansour