DavidCary: rough draft.

2015-02-17T20:02:30Z

rough draft.

New page

''Extremely rough draft''

How do I build a good hardware random number generator?

=== some applications of random numbers ===

Perhaps the most common application of random numbers is as part of the "https://" protocol for viewing websites.
It, like many cryptographic protocols,
uses special "one-time" nonce numbers
that ideally are generated by a hardware random number generator.

[http://wiki.openssl.org/index.php/Random_Numbers]

''After I build a hardware random number generator, what is a good way to feed the sequence of random numbers into such applications?''

==== radio? ====

A few [[projects#radio projects]]
"randomly" distribute the radio energy over a wide spectrum (spread spectrum).
They use something like a random number generator
to pick which frequency to use at any one instant.
However, as far as I am aware,
such systems never use unguessable hardware random number generators,
because the receiver
must be able to guess the sequence of frequencies used by the transmitter
(or vice-versa).
As far as I know,
non-military spread spectrum radios
don't even use a cryptographic pseudo-random sequence,
but (to make synchronization between receiver and transmitter easier
and to reduce cost and simplify the hardware)
always use some non-cryptographic pseudo-random sequence,
often a maximum-length sequence
(easy to construct with a linear-feedback shift register (LFSR)) or Gold code system.

=== a few more-or-less open-source HRNG designs ===

endolith / probably_random.ino :
Arduino hardware true random number generator
[https://gist.github.com/endolith/2568571]

[http://sockpuppet.org/blog/2014/02/25/safely-generate-random-numbers/]

Sergio Callegari; Riccardo Rovatti; and Gianluca Setti.
"Embeddable ADC-Based True Random Number Generator for Cryptographic Applications Exploiting Nonlinear Signal Processing and Chaos"
[http://ieeexplore.ieee.org/xpl/articleDetails.jsp?arnumber=1381779]
[http://www.researchgate.net/publication/3319163_Embeddable_ADC-based_true_random_number_generator_for_cryptographic_applications_exploiting_nonlinear_signal_processing_and_chaos]
[http://www.researchgate.net/profile/Sergio_Callegari/publication/3319163_Embeddable_ADC-based_true_random_number_generator_for_cryptographic_applications_exploiting_nonlinear_signal_processing_and_chaos/links/09e41511194d9d8d58000000.pdf]

"Infinite Noise TRNG (True Random Number Generator): The world's easist TRNG to get right"
by Bill Cox, who gives credit to Peter Allan.
[https://github.com/waywardgeek/infnoise]

DAV:
Callegari's ADC-Based True Random Number Generator looks very similar to the
"Infinite Noise TRNG"
approach.
What is the difference, if any?

[http://robseward.com/itp/adv_tech/random_generator/]

[http://www.cryogenius.com/hardware/rng/]

[https://lwn.net/Articles/525459/]

Whirlygig
[http://hackaday.com/2010/02/06/hardware-based-randomness-for-linux/]

whirlyfly
[https://github.com/zdavkeos/whirlyfly]

[http://forums.parallax.com/showthread.php/93061-Real-Random-Number-Generator-Object]

Some of these open-source hardware random number generators produce over 500 KBytes of high-quality randomness.
While pseudo-random number generators running on commodity desktop machines run many times faster, I find it hard to imagine any application for high-quality random numbers where 500 KBytes/s is "too slow".

[http://hackaday.com/2014/02/10/the-two-component-random-number-generator/]

Will Ware.
Hardware Random Bit Generator.
[http://web.jfet.org/hw-rng.html]

Hardware Random Number Generator
[http://iank.org/trng.html]
"(Yet Another) avalanche noise hardware random number generator"
" ... based upon a design by Will Ware."
" ... The final device, after moving the whitening logic to firmware
(for completeness sake, but at a significant speed expense),
achieved 9 kB/sec random data."

"The Hardware Random Number Generator" page
[http://www.ciphersbyritter.com/NEWS4/HARDRAND.HTM]
lots of discussion of theory.

...

"what is the best method of testing a hardware random number generator?"
[http://security.stackexchange.com/questions/47475/testing-a-hardware-random-number-generator]

I hear other people say that all modern Smart Cards contain a physical hardware random number generator
( [http://crypto.stackexchange.com/questions/20068/are-there-some-problems-to-use-pseudo-random-number-generator-in-smart-card] ).

=== sources of entropy ===

* noise from reverse biased transistor, which apparently is due to quantum tunneling.

* oscillator jitter (which requires at least 2 oscillators to detect),
which is apparently due to thermal noise (?)
(How can we tell that the 2 oscillators
are actually independent,
and have not accidentally become phase-locked?)

[http://www.quantiki.org/wiki/Quantum_Random_Number_Generators]

=== A few notes on HRNG theory ===

"As of 2004, the best random number generators have 3 parts:
an unpredictable nondeterministic mechanism,
entropy assessment, and
conditioner.
...
If the estimate is good, the the conditioned output bits are unbiased full-entropy bits even if the nondeterministic mechanism degrades over time.
In practice, the entropy assessment is the difficult part."
--
[http://en.wikibooks.org/wiki/Cryptography/Random_number_generation]

With a properly implemented randomness extractor, as long as the HRNG is in a physically secure room, most conceivable "attacks" (through-the-air electromagnetic interference, through-the-power-lines electromagnetic interference, etc.) at worst merely slow down the rate at which high-quality random bits are produced; they don't reduce the quality of whatever bits are produced. (The randomness extractor automatically compensates for any reduced quality of the internal raw data samples, throwing out "suspicious" samples).

=== further reading ===

* [http://crypto.stackexchange.com/questions/tagged/random-number-generator]

* [http://crypto.stackexchange.com/questions/tagged/pseudo-random-generator]

* [http://electronics.stackexchange.com/questions/tagged/random-number]

* [[Wikipedia: Hardware random number generator]]

Hardware random number generator - Revision history

DavidCary: rough draft.