[Cryptography] cheap sources of entropy (Bill Frantz)

[Arnold Reinhold]

On Sun, 19 Jan 2014 13:58,  Peter Trei inquired:
...
> 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.

Search for this thread on this list: "An alternative electro-mechanical entropy source" 12 Dec 2013. I suggested using a cheap accelerometer chip with a buzzer to insure some vibration and a small Arduino class microprocessor with USB interface.  Putting a low power microprocessor, an accelerometer and a small battery in a diskless black box device could allow it to collect entropy during shipment and have plenty available for initial startup key generation. It could also serve to detect excessive shocks during shipment, helping to justify the cost, which could be under a dollar or two in volume. For one off, you can get inexpensive modules from Digispark and Adafruit. 

As for cameras looking at a grey card in low light, it does depend on the camera, but it would be easy enough to test a specific model and cheap cameras are probably more suitable. Nonetheless, there is a lot to be said for pointing the camera at a real world chaotic image There will still be plenty of pixels whose low order bit is influence by Johnson noise (think about the line of transition in a gradient between grey scale n and greyscale n+1) and the images can be viewed periodically for verification. Some colored streamers in a server rack's fan exhaust should do, but I have always liked the aquarium approach. An air bubbler alone can provide tons of entropy (see this link http://www.thatpetplace.com/add-a-stone-airstone-6in-2in?). 

Arnold Reinhold

PS: In an earlier post I said CAESER's final portfolio was due at the end of 2107. That was a typo, I meant 2017, the date they give on their web site.