[149235] in cryptography@c2.net mail archive
Re: [Cryptography] cheap sources of entropy
daemon@ATHENA.MIT.EDU (Jon Callas)
Mon Jan 27 16:20:24 2014
X-Original-To: cryptography@metzdowd.com
From: Jon Callas <jon@callas.org>
In-Reply-To: <52DA388D.8040708@iang.org>
Date: Mon, 27 Jan 2014 12:57:28 -0800
To: ianG <iang@iang.org>
Cc: Cryptography <cryptography@metzdowd.com>, Jon Callas <jon@callas.org>
Errors-To: cryptography-bounces+crypto.discuss=bloom-picayune.mit.edu@metzdowd.com
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> 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 was more blunt -- leave the lens cap on, even. There is quantum noise in the sensor, and if you take a frame and hash it, it almost certainly has more true randomness than the width of your hash function.
If you are in doubt, take two pictures and hash them. Or whatever makes you comfy.
Jon
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