[Cryptography] cheap sources of entropy

[ianG]

On 18/01/14 06:04 AM, Bear wrote:

> Hmm.  It should not be too difficult to equip many servers in the same
> room with $10 USB cameras, and have them all pointed at a cheap,
> known-chaotic physical system like an aquarium with a bubbling filter,
> moving aquarium toys, and swimming fish -- all from different angles -- 
> running the resulting video, a half-second at a time, through a hash
> function, and using the results for "real" random numbers.  And it 
> amuses me that the sysadmin's job could legitimately include feeding
> the fish.


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.

When we were creating a CAcert root key at one stage, I used this
technique to deliver one of the independent feeds.  I wrote a shell
script to take a photo once a second, and sha it into a log file.
Examination with Mark-I eyeball of the photos and shas didn't reveal any
artifacts, and the results at any one point were certainly chaotic.

(In the same exercise, we XOR mixed in Linux's RNG and John Denker's
audio.  The goal was to have each person bring in an independent stream,
and then examine the XOR program to ensure it was clean.  About 2 pages
worth of simple C.)

Open question:  What do people think of the production of big important
keys using the old compliance method of "must use a HSM" now ?

iang