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Comment by gabrielblack | Hacker News Reader

I have some marbles and a crucifix ( that kind you hang on a wall) made of this material. I inherited them from my grandmother , the marbles was intended to be toys. The crucifix also is visible in the dark and it's the object with major emissions, but nothing dramatic. The marbles emit mostly alpha rays. Both can excite notably my Geiger counter, but, storing them in a metallic box, (i.e. that sheet metal box for biscuits ), no emission leaks. I'm using the marble in my DIY random number generator, based on a Geiger tube and an Arduino board.

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> I'm using the marble in my DIY random number generator, based on a Geiger tube and an Arduino board.

This is so nerdish, I love it!

So the crucifix is visible in the dark? This article makes it sound like a black light needed to observe the phenomenon, which strikes me as odd because I wouldn't have thought black lights were commonly available at the time when these first gained popularity.

The crucifix is different, besides the Uranium glass it has engravings painted with something I think is tritium.

That is a little scary - a bit into the territory of https://en.wikipedia.org/wiki/Radium_Girls

Let's say that my grandmother lived in times where the radiation was too much "mainstream": https://en.wikipedia.org/wiki/Shoe-fitting_fluoroscope

https://spectrum.ieee.org/fun-and-uranium-for-the-whole-fami...

and they was really close to create a world you can see in Fallout, the game:

https://en.wikipedia.org/wiki/Aircraft_Nuclear_Propulsion

https://en.wikipedia.org/wiki/Ford_Nucleon

https://en.wikipedia.org/wiki/Davy_Crockett_(nuclear_device)

How old is it? Tritium has a half life of only 12.3 years, so if it's more than 60 years or so old, there's basically none left (around 3%), certainly not enough to make it glow.

Radium is much more likely if it's still glowing.

More than 60, yes, maybe it's other source

Radium more likely. Tritium is produced in small quantities in nuclear reactors and is the fuel for fusion bombs. I doubt that was used to make a crucifix.

https://en.wikipedia.org/wiki/File:Tritium-watch.jpg https://en.wikipedia.org/wiki/Tritium_radioluminescence

Do you have a link or project site for the DIY random number generator? I'd like to read about it :)

I was thinking to make it public, but it's based on an Arduino shield I purchased the day after the Fukushima accident, it is no more in commerce. I should make it more generic changing hardware. I think you can find online similar projects.

Couldn't you just measure background radiation?

You don't have to look very hard to find entropy, but finding it in a cool and fun way is rare. This is way higher on both the functionality and fun scales than a wall of lava lamps.

My device, as other implementation, use the particle passing through the Geiger tube as a "virtual coin" , given a sampling frequency, if one or more particles are detected the firmware returns 1, if no particle is detected, zero. In other words, the random numbers are built a bit at time. My configuration with the background radiation returns too many zeros, so I needed something more ... lively. Anyway, what is the point to use the natural radiation if you have the serious stuff ? :-) When I say that the device is a nuclear RNG, peoples smile but when I turn it on and they listen the characteristic sound of a Geiger counter, the average reaction is "WHAAAAAATTTT ????". It's funny.

John Von Neumann’s method of creating a uniform distribution of random numbers from a skewed source (too many zeros) was:

“(From a stream of) bits, (take) two at a time (first and second, then third and fourth, and so on). If the two bits matched, no output was generated. If the bits differed, the value of the first bit was output … (this) can be shown to produce a uniform output even if the distribution of input bits is not uniform so long as each bit has the same probability of being one and there is no correlation between successive bits.” (Edited from Wikipedia)

Thank you for your valuable suggestion. Because the interest shown here, I decided to build an improved version ( I think during the Christmas vacations).

I have serious concerns about purchasing one and being put on "a list".

But this city is lackadaisical at best when it comes to industry. And we've had incidents where radioactive materials have been found in construction near homes.

So IDK. I feel like I probably should have one.

Having a counter, I think it's easy to found some source around, for example in surplus stores, etc. For example, old naval compass and clock are treated with tritium. You could find also rocks near the rivers with some interesting material.

My goal is to ensure I _don't_ have an interesting material near my dwelling. Considering I know of at least one case where some was discovered near a home and was probably there for 40 years.

Would that be cryptographically secure? Couldn't someone perturb an RNG based on background radiation by beaming radiation at it?

That shouldn't change anything: https://en.wikipedia.org/wiki/Fair_coin#Fair_results_from_a_...

That argument relies on independent samples, but if someone's beaming radiation at the device to control its output, the samples will not be independent.

It's not that easy to control radiation, controlling it to the level of individual decays is not possible.

The closest you can get is bring it closer/further, or shield/unshield.

I'd rather use a local source in a Faraday cage, so that it's not possible for someone to influence the output at all.

A Faraday cage is not going to block this type of radiation.

To test, I made a simple script generating the dispersion graph: the numbers seem to be of good quality

Maybe your grandmother purchased them from Bob Lazar: https://unitednuclear.com/index.php?main_page=product_info&c...

No, the color isn't the same. This is their color: https://www.google.com/url?sa=i&url=https%3A%2F%2Fwww.worthp...

whoosh

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