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

From: Stephan Mueller <smueller@chronox.de>
To: Pavel Machek <pavel@ucw.cz>
Cc: "Theodore Ts'o" <tytso@mit.edu>,
	sandy harris <sandyinchina@gmail.com>,
	linux-kernel@vger.kernel.org, linux-crypto@vger.kernel.org
Subject: Re: [PATCH] CPU Jitter RNG: inclusion into kernel crypto API and /dev/random
Date: Tue, 05 Nov 2013 14:45:58 +0100	[thread overview]
Message-ID: <7447932.fADKoNoZRI@tauon> (raw)
In-Reply-To: <4763730.CsXSbevC1J@tauon>

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.

That means with this approach, even another noise source is available 
that I could combine with the jitter measurements. 

I will have to perform more tests on that noise source. But the smoke 
test is already quite interesting.

Ciao
Stephan