Comments on: Hardware based randomness for Linux

By: Mein Senf

Mein Senf — Mon, 08 Feb 2010 22:05:00 +0000

http://www.kielnet.net/home/julien.thomas/tech/XR232WEB.htm

Simple and good one with rs232, unfortunately in german language.
http://translate.google.de/translate?js=y&prev=_t&hl=de&ie=UTF-8&layout=1&eotf=1&u=http%3A%2F%2Fwww.kielnet.net%2Fhome%2Fjulien.thomas%2Ftech%2FXR232WEB.htm&sl=de&tl=en&swap=1

By: cooperised

cooperised — Mon, 08 Feb 2010 13:28:11 +0000

CPDL -> CPLD

By: rj

rj — Sun, 07 Feb 2010 18:01:57 +0000

You can make “random” data that is completely white (i.e. flat FFT) in the frequency domain despite not being the least bit random. e.g. LFSRs.

By: rgh

rgh — Sun, 07 Feb 2010 12:30:53 +0000

“The problem with most hardware random number generators is failure detection. How do you know when the hardware craps out and starts generating a “less random” data stream?”

Take an FFT of the output to see what the spectrum is. If it’s flat then all is good otherwise it’s not.

By: Knappster

Knappster — Sun, 07 Feb 2010 03:13:16 +0000

For the average user it’s useless, but if your servers are handling a lot of ssl traffic it speeds things up a bit and provides a greater source of entropy.

By: Tachikoma

Tachikoma — Sun, 07 Feb 2010 01:45:45 +0000

I wonder how effective it would be to tap into junction noise of semiconductors, amplify them and feed that to a ADC.

By: Granmah

Granmah — Sun, 07 Feb 2010 01:41:13 +0000

so erm.. other than servers and security, how can this benefit the average user?

would it be overkill for irc ssl?

By: bothersaidpooh

bothersaidpooh — Sun, 07 Feb 2010 00:18:09 +0000

use a cmos camera and surplus lantern mantle?

failing that, a traser lamp epoxied to a photodiode would also work as the output from these is random.

By: Knappster

Knappster — Sat, 06 Feb 2010 21:31:48 +0000

You can buy entropy usb keys with fault, temp and randomness tests built in. I’ve seen one in use, makes ssh logins a lot faster :P http://www.entropykey.co.uk/

By: /dev/random

/dev/random — Sat, 06 Feb 2010 20:59:51 +0000

You can inject data into /dev/random, and it measures the entropy in what you give it. So if your RNG starts failing, it just wont use the data anymore (and tell you).

By: MrX

MrX — Sat, 06 Feb 2010 20:52:35 +0000

@localroger

I would like to try isolating a micro-controller tri-state pin from the environment and put it on low-impedance mode. I wonder how random the fluctuations on the readings will be.

By: localroger

localroger — Sat, 06 Feb 2010 20:21:59 +0000

There is an object for the Parallax Propeller which does pretty much this same thing using the on-chip counter-timer PLL’s.

By: MrX

MrX — Sat, 06 Feb 2010 20:01:10 +0000

@MS3FGX Is there any device which is “plug in and use forever”?

Yes, my dick.

I think Keith still have a point. HW-RNGs are mostly used for security applications and on those cases the randomness of that is critical.
Making the device check the randomness of its output and discard sets of samples who are not, would be a important security improvement IMHO.

By: MS3FGX

MS3FGX — Sat, 06 Feb 2010 19:48:36 +0000

Is there any device which is “plug in and use forever”? Of course a hardware RNG will eventually fail, just like anything else. It is no different from running occasional filesystem checks on a hard drive, you do spot checks on the system to make sure it is still working within certain tolerances.

That said, I am not sure how this relates to the project at hand. This device certainly doesn’t claim to be perfect, much less eternally perfect.

By: Keith

Keith — Sat, 06 Feb 2010 18:52:45 +0000

@MrX:

Yes, exactly.

My (not terribly well-made) point: hardware RNGs are not “plug in and use forever” devices; they require constant monitoring to ensure the quality of their output.