[148102] in cryptography@c2.net mail archive
Re: [Cryptography] randomness +- entropy
daemon@ATHENA.MIT.EDU (Bill Stewart)
Mon Nov 11 02:47:48 2013
X-Original-To: cryptography@metzdowd.com
Date: Fri, 08 Nov 2013 17:19:05 -0800
To: cryptography@metzdowd.com
From: Bill Stewart <bill.stewart@pobox.com>
In-Reply-To: <527D5146.40402@deadhat.com>
Errors-To: cryptography-bounces+crypto.discuss=bloom-picayune.mit.edu@metzdowd.com
At 01:01 PM 11/8/2013, David Johnston wrote:
>On 11/7/2013 11:08 AM, Jerry Leichter wrote:
>>The smartphone and the embedded system are *very* different. Any
>>phone has a microphone and a radio. Unfortunately, the radios are
>>usually sealed off so you couldn't use them as a source of radio
>>noise; but the microphones are wide open.
>I disagree about the 'sealed-off' thing.
Most smartphones have wifi, and can tell you things like signal
strength and noise levels on different channels, even if they don't
show you the cellular signals. It's probably not a rapidly-changing
signal, but it's going to have some entropy (and if there's not
enough noise, go microwave some coffee.) There's also typically an
accelerometer, and even dumb phones almost all have cameras.
But unfortunately, that $29 cable modem or dsl router isn't going to
have any spare hardware, even a 5-cent photocell, so it's network
noise only unless there's wifi.
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