[Cryptography] cheap sources of entropy (Bill Frantz)

[Peter Trei]

  Bill Frantz <frantz at pwpconsult.com> wrote


>
>
> On 1/18/14 at 12:17 AM, iang at iang.org (ianG) wrote:
>
> >Jon Callas (I think) a long time ago suggested pointing your cheapo USB
> >camera at a photographer's grey card in low light.  The theory is that
> >the cells in a camera seek for information and if they don't see
> >something that is worth reporting, it drives them a little tipsy.  The
> >claim is that this effect can drive them into some form of quantum
> >uncertainty.
>
> I think what is happening here is the effective ISO is being
> pushed up by the low light so there is a lot of noise in the
> amplifiers used to read out the sensor cells. What you are using
> is thermal noise in the amplifiers. You get a lot of readings in
> one photo, and it should be a good source.
>

One thought I've had on this applies only to wearables (smartphones,
mainly;
many contain accelerometers which allow them to determine orientation,
motion, etc.

Since these accelerometers are also used in very low power gadgets such
as fitness activity monitors, (Fitbit, etal), where they operate
continuously,
it seem plausible that they are cheap (in power terms) to run.

My suspicion is that these can act as a low-bandwidth source of entropy,
by the usual mechanisms involving timing of successive transitions.
producing
randomness which can be added to the pool.

Any thoughts? I expect this has been suggested before.

pt
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