My lesson from my personal experiments with Lavarand: you must have more than one lamp, not necessarily for more entropy, but for fail-over and uptime. At approximately ~30 hours, my vintage 70's lamp 'gives up' - the fluid temperature becomes pretty even between the bottom and the top. It's all essentially superheated as far as the wax is concerned and it simply stays in one place as a dome at the bottom, barely moving. This isn't good for creating random data. By using multiple lamps, it's possible to power cycle them. Ideally, every ten hours or so, remaining off for a couple hours.
We did this exact thing at SGI 20 years ago.
<a href="https://en.wikipedia.org/wiki/Lavarand" rel="nofollow">https://en.wikipedia.org/wiki/Lavarand</a><p>I wonder if Cloudflare was inspired by that.
I might be prejudiced, but this looks like a big PR stunt/done for the cool factor kind of thing. Aren't there simpler/saner alternatives for getting good randomness?
There's a good Tom Scott video on this too. Like most of his stuff, it's well worth the watch.<p><a href="https://youtu.be/1cUUfMeOijg" rel="nofollow">https://youtu.be/1cUUfMeOijg</a>
A lot of confusion in this discussion thread and other promotions of this idea stems from the intuition that you can "run out" of entropy in your random number pool if you don't periodically replenish it with a physically unpredictable source. I have had this intuition too. Two things that feed it are the Linux random(4) man page and the behavior of GPG when generating a new private key.<p>tptacek tried to explain some of the problems in this intuition at <a href="https://sockpuppet.org/blog/2014/02/25/safely-generate-random-numbers/" rel="nofollow">https://sockpuppet.org/blog/2014/02/25/safely-generate-rando...</a>, which relates to why he's so annoyed at some things people have said in this thread (and when discussing CSPRNG seeding in other places).<p>I like the idea of feeling physically unpredictable data into the CSPRNG, but for most purposes it's a misconception that doing so on an ongoing basis is in any way required by the design or that heavy users of randomness like CloudFlare would "run out of entropy" or "exhaust their entropy pool" if they didn't do so. The design of existing CSPRNGs would let CloudFlare use /dev/urandom for as long as it likes after securely seeding it just once, and there's no known cryptanalytic attack to which this practice would be vulnerable.
The Cloudflare blog posts that go into this in detail:<p><a href="https://blog.cloudflare.com/lavarand-in-production-the-nitty-gritty-technical-details/" rel="nofollow">https://blog.cloudflare.com/lavarand-in-production-the-nitty...</a><p><a href="https://blog.cloudflare.com/randomness-101-lavarand-in-production/" rel="nofollow">https://blog.cloudflare.com/randomness-101-lavarand-in-produ...</a>
More details on how it is implemented here: <a href="https://blog.cloudflare.com/lavarand-in-production-the-nitty-gritty-technical-details/" rel="nofollow">https://blog.cloudflare.com/lavarand-in-production-the-nitty...</a>
I did something similar a few years back, except instead of Lava lamps, I used a Geiger counter module connected to an Arduino (scrap from a project I was working on to make something economical for civilian use after the Fukushima Daiichi nuclear disaster). Basically, the background radiation is used as the PRNG number (not just as the seed). I found out later that someone at Sparkfun already did this: <a href="https://www.sparkfun.com/tutorials/132" rel="nofollow">https://www.sparkfun.com/tutorials/132</a>
This is pretty cool use of tech that goes back to SGI. It's definitely not the practical solution to TRNG's. There are analog solutions that use basic physics and EE techniques to generate noise fast, cheap, in tiny footprint if you want, and with a lot of potential diversity in supply chain. Here's an example of an open one:<p><a href="https://github.com/waywardgeek/infnoise/blob/master/README.md" rel="nofollow">https://github.com/waywardgeek/infnoise/blob/master/README.m...</a>
If Cloudflare ever open another office, they could use a wall full of Drinky Birds for randomness.<p><a href="https://en.wikipedia.org/wiki/Drinking_bird" rel="nofollow">https://en.wikipedia.org/wiki/Drinking_bird</a>
That's approximately 100 lava lamps each at 100W = 10,000W = 10kW/h * 20.4 cents = $2.04/h * 24 = $48.96/day $1,489.20/month.<p>Ignoring the fact that is very little money in Silicon Valley. Lava lamps consume a large amount of electricity in order to generate the heat they need. There are cheaper better ways to generate randomness, this is purely for spectacle clearly.<p>It makes me nervous more than anything. If that's the front they put up, inside is there a Rube Goldberg machine that triggers DDoS protection?
Cloudflare's own blog posts about this:<p><a href="https://blog.cloudflare.com/lavarand-in-production-the-nitty-gritty-technical-details/" rel="nofollow">https://blog.cloudflare.com/lavarand-in-production-the-nitty...</a><p><a href="https://blog.cloudflare.com/randomness-101-lavarand-in-production/" rel="nofollow">https://blog.cloudflare.com/randomness-101-lavarand-in-produ...</a>
One of my common daydreams is designing entropy-generating setups like this. Just last week I went on a brewery tour (Bell's) and stared at the bottling plant for a while, admiring the chaos of the bottles bumping into each other as the path turns and narrows.
A variation on Brownian Motion: <a href="https://en.wikipedia.org/wiki/Brownian_motion" rel="nofollow">https://en.wikipedia.org/wiki/Brownian_motion</a>
If you can't afford that many lava lamps, NIST provides an alternative, free service:<p><a href="https://beacon.nist.gov/home" rel="nofollow">https://beacon.nist.gov/home</a>
How do they prevent the camera or its outgoing feed from being hacked or replaced by the NSA?<p>Edit: I see this is addressed partially by wkandek's link elsewhere in this discussion.
Reminded me about the dice-o-matic<p><a href="https://news.ycombinator.com/item?id=14806986" rel="nofollow">https://news.ycombinator.com/item?id=14806986</a>
It's worth nothing that the lava lamps are visible street side through large glass windows, so it serves as an eye-catching artpiece for passerbys.
> Since computer codes are created by machines with relatively predictable patterns, it is entirely possible for hackers to guess their algorithms, posing a security risk.<p>That’s not what “computer codes” and “algorithms” mean.
Generating a random number by using microseconds as a seed is more than enough for practically every single case. It still hasn't been cracked or predicted.<p>Some people say that, in theory, it could be cracked however, i tried and its impossible, modern computers are so complex and fast that it gives enough entropy.
Seems like a waste of energy... I can imagine putting a weather station on the roof would be more useful (albeit less cool). Use multiple sensors for rainfall, UV, wind speed, wind direction, temperature, pressure and aggregate the signals from each... Surely the combination of localized weather readings would provide enough randomness.
It's open to the public‽ Seems like a bad idea to let a potential spy in there to set up a camera and de-randomize this source of random info. Also, the headline on HN declares it a fact that the lava lamps are assisting in the encryption, but the article is careful to say "maybe", "might", etc.<p>This seems wildly insecure and much more likely to represent a weak link than to actually aid in randomness.