linux-kernel - Re: [PATCH] CPU Jitter RNG: inclusion into kernel crypto API and /dev/random

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Message-ID: <6186307.PQMXWdkvke@tauon>
Date:	Wed, 06 Nov 2013 12:42:47 +0100
From:	Stephan Mueller <smueller@...onox.de>
To:	Pavel Machek <pavel@....cz>
Cc:	Theodore Ts'o <tytso@....edu>,
	sandy harris <sandyinchina@...il.com>,
	linux-kernel@...r.kernel.org, linux-crypto@...r.kernel.org
Subject: Re: [PATCH] CPU Jitter RNG: inclusion into kernel crypto API and /dev/random

Am Dienstag, 5. November 2013, 14:45:58 schrieb Stephan Mueller:

Hi Pavel,

>Am Dienstag, 5. November 2013, 13:25:40 schrieb Stephan Mueller:
>
>Hi Pavel,
>
>>Am Montag, 4. November 2013, 00:32:07 schrieb Pavel Machek:
>>>But they usually _do_ have RTC or other clock, not driven by CPU
>>>oscilator. Good.
>>>
>>>What about just
>>>
>>>while (!enough_entropy) {
>>>
>>>      cur_time = read_rtc();
>>>      simulated_tsc = 0;
>>>      while (cur_time == read_rtc())
>>>      
>>>      	    simulated_tsc++;
>>>      
>>>      gain_entropy_from(simulated_tsc)
>>>
>>>}
>>
>>That is an interesting piece of code -- what would you do in the
>>gain_entropy_from function?
>
>Please disregard my question.
>
>I plugged that idea into my current Jitter RNG processing and disabled
>the other jitter measurements to get a clear, isolated picture.
>
>The result is also a white noise! And it is even quite fast.

After doing some more research on this approach, I have to admit that 
the output not good (i.e. white noise) in all situations. Therefore, I 
dropped that (for now).

But thank you very much for your suggestion.

Ciao
Stephan
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