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A wall of lava lamps helps encrypt the internet

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Re: A wall of lava lamps helps encrypt the internet

#151

Post by schoen »

JdeBP wrote: post #148
Bromskloss wrote: post #142

Earlier quoted context omitted.

I've read that post now and previously (though not its references) and I feel that it never gets to the point where it explains how urandom can be equally safe as random. Is the idea not that it is information-theoretically safe, but rather that the computational requirements are too great to figure out the state of the random-number generator even after a large amount of observed output?

Then you might find that Thomas Hühn's approach helps you. * https://www.2uo.de/myths-about-urandom/ The "another crypto expert" mentioned by schoen is Daniel J. Bernstein, quoted directly by Hühn.

Indeed, thanks! That was the other piece that I was thinking of and couldn't find right away.

Re: A wall of lava lamps helps encrypt the internet

#152

Post by disillusioned »

jstanley wrote: post #53
rm999 wrote: post #23

Earlier quoted context omitted.

For sure. In another office they use a geiger counter (a much more standard way to get randomness, and probably easier to setup). That said, this doubles as a public art installation in their lobby - something many companies spend thousands (or millions!) of dollars on. So it's not just PR, it's actually surprisingly practical.

If it was a public art installation, wouldn't that leak their entropy?

Short of them actually publishing the image signature the camera takes as the random input, no. Imagine just how much sensor noise is sitting across the image, and figure on other elements others have mentioned: the angle, the aperture, etc. I imagine two near-identical frames without any movement between them taken on a single camera might still have a significant amount of entropy between them, especially if you're using the camera raw data, for those reasons.

They (CF) discuss this on their deep dive:

>>>The flow of the “lava” in a lava lamp is very unpredictable,6 and so the entropy in those lamps is incredibly high. Even if we conservatively assume that the camera has a resolution of 100x100 pixels (of course it’s actually much higher) and that an attacker can guess the value of any pixel of that image to within one bit of precision (e.g., they know that a particular pixel has a red value of either 123 or 124, but they aren’t sure which it is), then the total amount of entropy produced by the image is 100x100x3 = 30,000 bits (the x3 is because each pixel comprises three values - a red, a green, and a blue channel). This is orders of magnitude more entropy than we need. [1]

1: https://blog.cloudflare.com/lavarand-in-production-the-nitty...

Re: A wall of lava lamps helps encrypt the internet

#153

Post by jstanley »

disillusioned wrote: post #152
jstanley wrote: post #53

Earlier quoted context omitted.

If it was a public art installation, wouldn't that leak their entropy?

Short of them actually publishing the image signature the camera takes as the random input, no. Imagine just how much sensor noise is sitting across the image, and figure on other elements others have mentioned: the angle, the aperture, etc. I imagine two near-identical frames without any movement between them taken on a single camera might still have a significant amount of entropy between them, especially if you're…

If the information encoded in the lava lamps is not important for the entropy, why do they even need to be there?

If it just needs to be some image, and it doesn't actually matter if others know what it can see, why not just point the camera at a normal lamp, or an empty room, or the sky?

Re: A wall of lava lamps helps encrypt the internet

#154

Post by crazyhatfish »

jstanley wrote: post #153
disillusioned wrote: post #152

Earlier quoted context omitted.

Short of them actually publishing the image signature the camera takes as the random input, no. Imagine just how much sensor noise is sitting across the image, and figure on other elements others have mentioned: the angle, the aperture, etc. I imagine two near-identical frames without any movement between them taken on a single camera might still have a significant amount of entropy between them, especially if you're…

If the information encoded in the lava lamps is not important for the entropy, why do they even need to be there? If it just needs to be some image, and it doesn't actually matter if others know what it can see, why not just point the camera at a normal lamp, or an empty room, or the sky?

It is, the author is just saying that even without it they still have enough entropy in the system to be secure enough.

Any old image doesn't have pretty strong random number generators in it.

Re: A wall of lava lamps helps encrypt the internet

#155

Post by Bromskloss »

JdeBP wrote: post #148
Bromskloss wrote: post #142

Earlier quoted context omitted.

I've read that post now and previously (though not its references) and I feel that it never gets to the point where it explains how urandom can be equally safe as random. Is the idea not that it is information-theoretically safe, but rather that the computational requirements are too great to figure out the state of the random-number generator even after a large amount of observed output?

Then you might find that Thomas Hühn's approach helps you. * https://www.2uo.de/myths-about-urandom/ The "another crypto expert" mentioned by schoen is Daniel J. Bernstein, quoted directly by Hühn.

I guess this kind of, maybe, explains it, though in an oblique way, and even that only because I was already on the lookout for something about information-theoretical security vs. computational security.

It mostly brings up misconceptions I never had, and attacks those. For example, why would it matter that /dev/random gets its output from the same CSPRNG as /dev/urandom (or any other CSPRNG)? Shouldn't the output of the CSPRNG, assuming its state is large enough, contain as much entropy as its input?

The focus on giving me orders about what I should do, rather than telling me why, also gets old somewhere around the first time.

Re: A wall of lava lamps helps encrypt the internet

#156

Post by JdeBP »

tptacek wrote: post #90
mbesto wrote: post #85

Earlier quoted context omitted.

Yes, the article and the form in which it is exhibited is a PR stunt. However, that doesn't mean it's not practical in any capacity....if you locked this away in a room and never told anyone, it would still hold a utility for the company. Are there alternatives? Sure, but again that doesn't make it impractical. It's also a fairly novel way to explain to people that `random()` isn't truly random.

It is unlikely that it holds any utility, or that it is practical in any capacity.

The writing by Cloudflare on the subject (hyperlinked here several times already, so I won't) indicates that the utility that Cloudflare sees in it is in militating against the sort of malicious entropy source attacks described by Bernstein. The idea is that one has a set of disparately placed entropy sources, in Cloudflare's head office (of which the lava lamps are just one) and in Cloudflare's data centre, making it hard to supplant one and simultaneously observe all of the others.

I am not sure that Cloudflare is correct about this, however. It seems to me that at the point where the entropy sources are finally mixed, on the beacon machine in the datacentre, it does not matter that the lava lamps are far away, and this factor is just window dressing. The data that they generate has to arrive at the beacon machine on a serial port, Ethernet interface, or other input device, and that is the point where it can be observed/supplanted.

Re: A wall of lava lamps helps encrypt the internet

#157

Post by mmjaa »

oppositelock wrote: post #36

We did this exact thing at SGI 20 years ago. https://en.wikipedia.org/wiki/Lavarand I wonder if Cloudflare was inspired by that.

Before SGI, there was the Aquari-rand, but I can't find a link for it. Basically an Aquarium with a digital camera pointed at it..
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