To collect this data, Cloudflare has arranged about 100 lava lamps on one of the walls in the lobby of the Cloudflare headquarters and mounted a camera pointing at the lamps. The camera takes photos of the lamps at regular intervals and sends the images to Cloudflare servers. All digital images are really stored by computers as a series of numbers, with each pixel having its own numerical value, and so each image becomes a string of totally random numbers that the Cloudflare servers can then use as a starting point for creating secure encryption keys.
I’m sure they’re smarter than me but my novice cryptographer brain doesn’t understand this.
Isn’t the string of numbers representing each pixel rather limited Aren’t all those sections of the image that have lava lamps limited to values somewhere in the reddish/blueish spectrum? Isn’t the gray background very non-random?
Apparently the camera is accessible in the lobby. They say people walking in front of the camera adds randomness. If I go there and hold a photo in front of the camera which I know the values of, doesn’t that compromise everything?
To be fair their site says they take the lava lamp output and combine it with entropy from two servers and probably do a lot of other stuff before actually getting random numbers. But I don’t get how the lava lamps photo setup is even close to being random
But different doesn’t mean random. An attacker could test every possibility for that pixel rather quickly. Even faster if you know a bunch of the pixels are, for example, a shade of gray.
I found an explanation where they bring up the issues I brought up as well as some others.
They give an example with one red value for a single pixel. They don’t address my point that there are a lot of pixels like that one, maybe not all would be 50/50 like their example but a lot of pixels would have a much narrower range of values than randomness.
But they answer my second point about a hacker putting something in front of the camera with known values and that answer sort of takes care of everything. It boils down to, it doesn’t matter because the lava lamp wall output is mixed with other sources that an attacker doesn’t have access to.
Cloudflare uses a wall of lava lamps for some of their RNG needs
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I’m sure they’re smarter than me but my novice cryptographer brain doesn’t understand this.
Isn’t the string of numbers representing each pixel rather limited Aren’t all those sections of the image that have lava lamps limited to values somewhere in the reddish/blueish spectrum? Isn’t the gray background very non-random?
Apparently the camera is accessible in the lobby. They say people walking in front of the camera adds randomness. If I go there and hold a photo in front of the camera which I know the values of, doesn’t that compromise everything?
To be fair their site says they take the lava lamp output and combine it with entropy from two servers and probably do a lot of other stuff before actually getting random numbers. But I don’t get how the lava lamps photo setup is even close to being random
tried and failed to add image, so here a link: https://www.cloudflare.com/learning/ssl/lava-lamp-encryption/
If you hash the image with a strong algo, even a single different pixel should end up in a wildly different result.
But different doesn’t mean random. An attacker could test every possibility for that pixel rather quickly. Even faster if you know a bunch of the pixels are, for example, a shade of gray.
I found an explanation where they bring up the issues I brought up as well as some others.
https://blog.cloudflare.com/lavarand-in-production-the-nitty-gritty-technical-details/
They give an example with one red value for a single pixel. They don’t address my point that there are a lot of pixels like that one, maybe not all would be 50/50 like their example but a lot of pixels would have a much narrower range of values than randomness.
But they answer my second point about a hacker putting something in front of the camera with known values and that answer sort of takes care of everything. It boils down to, it doesn’t matter because the lava lamp wall output is mixed with other sources that an attacker doesn’t have access to.
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