9 ms·

What makes randomness so hard? I had this crazy thought awhile back and wondering if it would work out: Say you took a small disk shaped object like a hockey

What makes randomness so hard? I had this crazy thought awhile back and wondering if it would work out: Say you took a small disk shaped object like a hockey puck with a window on it and you filled it with sand. 50% white sand and 50% black sand. Inside the puck would be blades that are attached to a motor and rotated slowly to constantly change the pattern. The pattern formed in the window would be truly random wouldn't it? You could mount this to a PCIE card with a camera...

zodiac 10y ago
https://en.wikipedia.org/wiki/Hardware_random_number_generator https://en.wikipedia.org/wiki/Hardware_random_number_generat...
Tomte 10y ago
Mechanical devices utilizing some form of chaotic behavior are usually pretty good sources of randomness, but they have a really high probability of malfunctioning (when your motor stops, you get predictable outputs), the are subject to wear-and-tear, and their entropic properties can be hard to quantify. And they are less cool than avalanche noise, when you're asking nerds like us. IMHO, one of the best devices to get low amounts of randomness is still the dice (cube). Casino-grade, if you're anal about it. I use that to throw Diceware passphrases.
- jbclements 10y ago
  Shameless plug (of my FOSS): if you like Diceware, you might like Molis Hai even better. Maps the 56-bit sequence 0x556bfdce0148c9 to "wrowd aut settea". I betcha the corresponding diceware passphrase is way longer and less memorable. cf https://www.brinckerhoff.org/molis-hai/pwgen.html https://www.brinckerhoff.org/molis-hai/pwgen.html, or download FOSS repo from github.
  - Tomte 10y ago
    What's that? Gaelic? Old English? I'd certainly dispute the "memorable" part for most people on Earth.
    - rincebrain 10y ago
      I haven't looked at the source, but the linked page claims to use a Markov model trained on an English corpus (in this case, A Tale of Two Cities), so it emits English-like sequences of letters and spacing, and uses that in conjunction with a Huffman tree setup to map random bitstrings to the pseudo-English phrases. You could use this on $LANGUAGE of your choice, or $CORPUS of your choice. (Also, it seems much more memorable to me than an equivalent random stream of bits are.)
      - Tomte 10y ago
        Ah, English-like. Not English. That eluded me. Still, neither "wrowd", nor "aut", nor "settea" looks or sounds English-like to me. I wouldn't even begin to know how to pronounce it. It's nice in a sense, sure, but I suppose I could even remember (real) French words better, despite all those accents and me not speaking French.
        garethrees 10y ago
        "wrowd": a portmanteau for "wrong crowd". "Take care, you don't want to hang out with the wrowd". "aut": a logarithmic unit of measurement indicating the level of automation of a process. "I think we can get another couple of auts out of the sentiment-analysis pipeline." "settea": a genus of shrubs in the family Settaceae.
        JoeAltmaier 10y ago
        Re: wrowd. The term 'OK' originally meant 'Our Kind'. There was another term "NOK" meaning "Not Our Kind" which got lost. Now we have wrowd, maybe it will fare better.
        thaumasiotes 10y ago
        > The term 'OK' originally meant 'Our Kind'. There was another term "NOK" meaning "Not Our Kind" which got lost. I frown on casually lying to people over the internet. The term 'OK' originally stood for 'all correct'. http://www.etymonline.com/index.php?term=OK http://www.etymonline.com/index.php?term=OK http://www.straightdope.com/columns/read/503/what-does-ok-stand-for http://www.straightdope.com/columns/read/503/what-does-ok-st... You're trying to allude to NOKD, which is (1) completely unrelated, and (2) not lost.
  - lmm 10y ago
    I get "aaron nitty ms exxon inept" for the same value in Diceware (with a few bits spare, hence "aaron" from near the start of the alphabet). Subjective but I think that's more memorable.
    - jbclements 10y ago
      quite a bit longer, though...
      - lmm 10y ago
        Sure, but how does the raw length matter? The computer is storing it hashed anyway; the human can probably type five actual words faster than 3 pseudo-words.
eyeJam 10y ago
I don't really know what I'm talking about here but... If two such devices were identical in every way and started from the same conditions (i.e: the sands were placed in the devices the exact same way) then over a sufficient amount of time the sand mixture in the two devices would reach an identical equilibrium state of mixing. At least that's how two gases would act. No idea about sand.
- Tomte 10y ago
  Your "if" is pretty much untenable. Find me two identical sand particles. Your argument basically boils down to "chaos theory is wrong, because I /can/ know everything".
  - jacobush 10y ago
    It does not boil down to that I think. It was a good question which got enlightening answers.
    - Tomte 10y ago
      It got one other answer, which was not terribly different.
      - jacobush 10y ago
        Yes both good
- Mtinie 10y ago
  Sure, eventually. At the same point in time that the monkeys produced "Hamlet" on a bunch of typewriters. The problem is the number of entry variables -- even if the starting position was X, the affects of gravity, friction, and general entropy would result in different states.
_greim_ 10y ago
What you describe is essentially a hardware-based source of randomness. These devices sample various kinds of random physical processes to produce random streams of data. None of them are perfect but some are really good. For example, perhaps the black grains have a slightly different density, so they might tend to congregate more on the upper or lower side of the window, ever so slightly.
- fnbr 10y ago
  Wouldn't that change the distribution but not the randomness?
  - eru 10y ago
    Depends on what you mean by randomness. In general, natural processes seldom produce perfectly unbiased streams of independent coin flips. There's usually some post processing.
cjslep 10y ago
People that want seriously random numbers use radioactive decay because the underlying physical phenomena (described via quantum mechanics) is fundamentally random and cannot predict the time, energy, and direction of decay all at the same time (as far as my limited understanding is aware).
- johncolanduoni 10y ago
  > cannot predict the time, energy, and direction of decay all at the same time The uncertainty principle isn't the aspect of quantum mechanics that is used in these RNGs. They only need the fact that they can perform an action (measurement of some observable) whose outcome is not predictable. They do not attempt to measure different observables, since this would not help produce randomness. It is in essence just a (theoretically ideal) dice roll.
- wyager 10y ago
  >underlying physical phenomena (described via quantum mechanics) is fundamentally random This is one interpretation of QM. There are many theories explaining eigenbasis collapse (the "random-looking" phenomenon), and some of them are deterministic. The important thing here is that the data stream is hard or impossible to predict. It doesn't have to be truly random, because we don't even know if "truly random" is a sensible thing to ask for. What we're actually hoping is that you can't predict the result of a measurement, whether or not it's because of randomness or something else. Most RNGs also don't rely on the uncertainty principle (or, more generally, non-commutative measurements), but instead on e.g. radioactive decay. This is an eigenbasis collapse mechanism (with the two eigenstates being "this thing hasn't decayed" or "this thing has decayed"), but it's not based on uncertainty. This is easier to build physically.
- haikuginger 10y ago
  Here's a great example of radioactive decay in use as a source of entropy[0]. Essentially, each component of a nuclear weapon derives its own private key at time of assembly from the radiation of the weapon itself, and saves the public keys of all the other components; thereafter, it'll only respond to signed communication from those other components. Basically, it removes the possible attack vector of replacing any command-and-control circuitry with your own, suborned, components. [0] - https://www.llnl.gov/news/lawrence-livermore-scientist-develops-uncrackable-code-nuclear-weapons https://www.llnl.gov/news/lawrence-livermore-scientist-devel...
digler999 10y ago
how do you know the two colors of sand will weigh the same amount ? if not, over time the heavy sand will sink and "sort" the color. Over time the sand could (perhaps) grind itself into flour and not exude the same mechanical properties anymore. Finally, even if that worked, it might be good for what, 2,3, maybe 5 samples per second. If you take too many pictures before the sand moves, it's no longer random. What if I need millions of random numbers ?
- eru 10y ago
  You use a randomness extractor like http://www.eecs.harvard.edu/~michaelm/coinflipext.pdf http://www.eecs.harvard.edu/~michaelm/coinflipext.pdf (or more sophisticated) to generate the actual unbiased random numbers from your source.
Tepix 10y ago
You can try to extract the random noise of a webcam CCD sensor, no need to move mechanical parts that are prone to failure. ObLink: http://www.lavarnd.org/what/process.html http://www.lavarnd.org/what/process.html
mserdarsanli 10y ago
http://dilbert.com/strip/2001-10-25 http://dilbert.com/strip/2001-10-25

zodiac 10y ago

https://en.wikipedia.org/wiki/Hardware_random_number_generator https://en.wikipedia.org/wiki/Hardware_random_number_generat...

Tomte 10y ago

Mechanical devices utilizing some form of chaotic behavior are usually pretty good sources of randomness, but they have a really high probability of malfunctioning (when your motor stops, you get predictable outputs), the are subject to wear-and-tear, and their entropic properties can be hard to quantify. And they are less cool than avalanche noise, when you're asking nerds like us. IMHO, one of the best devices to get low amounts of randomness is still the dice (cube). Casino-grade, if you're anal about it. I use that to throw Diceware passphrases.

jbclements 10y ago
Shameless plug (of my FOSS): if you like Diceware, you might like Molis Hai even better. Maps the 56-bit sequence 0x556bfdce0148c9 to "wrowd aut settea". I betcha the corresponding diceware passphrase is way longer and less memorable. cf https://www.brinckerhoff.org/molis-hai/pwgen.html https://www.brinckerhoff.org/molis-hai/pwgen.html, or download FOSS repo from github.
- Tomte 10y ago
  What's that? Gaelic? Old English? I'd certainly dispute the "memorable" part for most people on Earth.
  - rincebrain 10y ago
    I haven't looked at the source, but the linked page claims to use a Markov model trained on an English corpus (in this case, A Tale of Two Cities), so it emits English-like sequences of letters and spacing, and uses that in conjunction with a Huffman tree setup to map random bitstrings to the pseudo-English phrases. You could use this on $LANGUAGE of your choice, or $CORPUS of your choice. (Also, it seems much more memorable to me than an equivalent random stream of bits are.)
    - Tomte 10y ago
      Ah, English-like. Not English. That eluded me. Still, neither "wrowd", nor "aut", nor "settea" looks or sounds English-like to me. I wouldn't even begin to know how to pronounce it. It's nice in a sense, sure, but I suppose I could even remember (real) French words better, despite all those accents and me not speaking French.
      - garethrees 10y ago
        "wrowd": a portmanteau for "wrong crowd". "Take care, you don't want to hang out with the wrowd". "aut": a logarithmic unit of measurement indicating the level of automation of a process. "I think we can get another couple of auts out of the sentiment-analysis pipeline." "settea": a genus of shrubs in the family Settaceae.
        JoeAltmaier 10y ago
        Re: wrowd. The term 'OK' originally meant 'Our Kind'. There was another term "NOK" meaning "Not Our Kind" which got lost. Now we have wrowd, maybe it will fare better.
        thaumasiotes 10y ago
        > The term 'OK' originally meant 'Our Kind'. There was another term "NOK" meaning "Not Our Kind" which got lost. I frown on casually lying to people over the internet. The term 'OK' originally stood for 'all correct'. http://www.etymonline.com/index.php?term=OK http://www.etymonline.com/index.php?term=OK http://www.straightdope.com/columns/read/503/what-does-ok-stand-for http://www.straightdope.com/columns/read/503/what-does-ok-st... You're trying to allude to NOKD, which is (1) completely unrelated, and (2) not lost.
- lmm 10y ago
  I get "aaron nitty ms exxon inept" for the same value in Diceware (with a few bits spare, hence "aaron" from near the start of the alphabet). Subjective but I think that's more memorable.
  - jbclements 10y ago
    quite a bit longer, though...
    - lmm 10y ago
      Sure, but how does the raw length matter? The computer is storing it hashed anyway; the human can probably type five actual words faster than 3 pseudo-words.

eyeJam 10y ago

I don't really know what I'm talking about here but... If two such devices were identical in every way and started from the same conditions (i.e: the sands were placed in the devices the exact same way) then over a sufficient amount of time the sand mixture in the two devices would reach an identical equilibrium state of mixing. At least that's how two gases would act. No idea about sand.

Tomte 10y ago
Your "if" is pretty much untenable. Find me two identical sand particles. Your argument basically boils down to "chaos theory is wrong, because I /can/ know everything".
- jacobush 10y ago
  It does not boil down to that I think. It was a good question which got enlightening answers.
  - Tomte 10y ago
    It got one other answer, which was not terribly different.
    - jacobush 10y ago
      Yes both good
Mtinie 10y ago
Sure, eventually. At the same point in time that the monkeys produced "Hamlet" on a bunch of typewriters. The problem is the number of entry variables -- even if the starting position was X, the affects of gravity, friction, and general entropy would result in different states.

_greim_ 10y ago

What you describe is essentially a hardware-based source of randomness. These devices sample various kinds of random physical processes to produce random streams of data. None of them are perfect but some are really good. For example, perhaps the black grains have a slightly different density, so they might tend to congregate more on the upper or lower side of the window, ever so slightly.

fnbr 10y ago
Wouldn't that change the distribution but not the randomness?
- eru 10y ago
  Depends on what you mean by randomness. In general, natural processes seldom produce perfectly unbiased streams of independent coin flips. There's usually some post processing.

cjslep 10y ago

People that want seriously random numbers use radioactive decay because the underlying physical phenomena (described via quantum mechanics) is fundamentally random and cannot predict the time, energy, and direction of decay all at the same time (as far as my limited understanding is aware).

johncolanduoni 10y ago
> cannot predict the time, energy, and direction of decay all at the same time The uncertainty principle isn't the aspect of quantum mechanics that is used in these RNGs. They only need the fact that they can perform an action (measurement of some observable) whose outcome is not predictable. They do not attempt to measure different observables, since this would not help produce randomness. It is in essence just a (theoretically ideal) dice roll.
wyager 10y ago
>underlying physical phenomena (described via quantum mechanics) is fundamentally random This is one interpretation of QM. There are many theories explaining eigenbasis collapse (the "random-looking" phenomenon), and some of them are deterministic. The important thing here is that the data stream is hard or impossible to predict. It doesn't have to be truly random, because we don't even know if "truly random" is a sensible thing to ask for. What we're actually hoping is that you can't predict the result of a measurement, whether or not it's because of randomness or something else. Most RNGs also don't rely on the uncertainty principle (or, more generally, non-commutative measurements), but instead on e.g. radioactive decay. This is an eigenbasis collapse mechanism (with the two eigenstates being "this thing hasn't decayed" or "this thing has decayed"), but it's not based on uncertainty. This is easier to build physically.
haikuginger 10y ago
Here's a great example of radioactive decay in use as a source of entropy[0]. Essentially, each component of a nuclear weapon derives its own private key at time of assembly from the radiation of the weapon itself, and saves the public keys of all the other components; thereafter, it'll only respond to signed communication from those other components. Basically, it removes the possible attack vector of replacing any command-and-control circuitry with your own, suborned, components. [0] - https://www.llnl.gov/news/lawrence-livermore-scientist-develops-uncrackable-code-nuclear-weapons https://www.llnl.gov/news/lawrence-livermore-scientist-devel...

digler999 10y ago

how do you know the two colors of sand will weigh the same amount ? if not, over time the heavy sand will sink and "sort" the color. Over time the sand could (perhaps) grind itself into flour and not exude the same mechanical properties anymore. Finally, even if that worked, it might be good for what, 2,3, maybe 5 samples per second. If you take too many pictures before the sand moves, it's no longer random. What if I need millions of random numbers ?

eru 10y ago
You use a randomness extractor like http://www.eecs.harvard.edu/~michaelm/coinflipext.pdf http://www.eecs.harvard.edu/~michaelm/coinflipext.pdf (or more sophisticated) to generate the actual unbiased random numbers from your source.

Tepix 10y ago

You can try to extract the random noise of a webcam CCD sensor, no need to move mechanical parts that are prone to failure. ObLink: http://www.lavarnd.org/what/process.html http://www.lavarnd.org/what/process.html

mserdarsanli 10y ago

http://dilbert.com/strip/2001-10-25 http://dilbert.com/strip/2001-10-25