WEBVTT
Kind: captions
Language: en

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Computers aren't very good
at picking random numbers.

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Every part of a computer is
designed to be predictable,

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and to follow logical patterns.

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You put the same numbers in,

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you're going to get the same numbers out.

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Which is a problem, because
all modern encryption,

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including that padlock up in your browser

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that tells you that you're safe,

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all of that relies on big,
properly random numbers.

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If you can somehow predict those numbers,

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you can start breaking those locks.

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Which is why I'm here,

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at the headquarters of Cloudflare,
in San Francisco.

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Cloudflare is a service that protects
websites and web services,

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and sort of sits in front of them
as a gatekeeper.

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Somewhere around 10% of the web
flows through Cloudflare's network.

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Cloudflare was one of the first companies

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to provide free SSL
encryption for websites.

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So the connection between your web browser
and the website you're going to

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is fully encrypted and
invisible for eavesdroppers

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to be able to look at.

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In short, these folks deal with a lot of
encrypted Internet traffic,

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so they need a lot of random numbers.

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It is possible to write code
that will simulate randomness,

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and that's good enough for a lot of uses,

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but in theory, those
numbers could be predicted.

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They're just being generated by code,

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so the servers here have to get their
randomness

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from an external and
entirely unpredictable source.

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A lot of home computers treat their own
users as sources of randomness,

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tiny twitches of mouse movement,

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the exact milliseconds between keystrokes,

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or on a phone maybe even the
accelerometer or other sensors.

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In all those cases, they generally discard
the bigger parts,

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the bits that could just
be influenced by humans,

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and go off the tiny little decimal places,

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the bits that you couldn't
control precisely,

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even if you wanted to.

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But that sort of human
interaction is nowhere

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near enough for an
operation on this scale,

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hence lava lamps.

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We videotape these lava lamps
and take the pictures and video,

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and turn it into a stream of
random, unpredictable bytes.

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And this unpredictable data is what we use
to help create the keys

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that encrypt the traffic that
flows through Cloudflare's network.

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This data is then fed
into our data centres

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and then fed into the Linux kernel which

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then uses it to help seed
random number generators

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that are used to generate keys.

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Every time that you take
a picture with a camera

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there's going to be some sort of static,
some sort of noise.

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So it's not only just where the bubbles
are flowing through the lava lamp,

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it's the state of the air,
the ambient light,

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every tiny change impacts
the stream of data.

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A cryptographic hash function
is something that we use

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where even if you have one static image
and one little bit changes,

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it changes the entire stream.

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So we use that to help
scatter the randomness

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as much as possible.

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We also collect randomness
around the world.

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So in our London office,
we have this thing

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called a chaotic pendulum.

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It has three pieces and
it's unpredictable in

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which way they twist and turn together.

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We videotape that and feed it into our
randomness source, as well.

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In our Singapore office, we
have a radioactive source

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that we use to feed into the
randomness system, as well.

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So this is not just some
stunt that we pulled,

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it's actually being
fed into our real systems.

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Whether anything in
the world is truly random

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is arguably a question of
philosophy and not science.

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Maybe everything is just
complicated clockwork.

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But these lava lamps are so chaotic

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that simulating that camera shot
with perfect pixel accuracy,

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far enough ahead
to be useful

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while figuring out everything else
those images are being put through,

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it's roughly the same level of difficulty
as just brute-forcing the encryption in the first place.

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And even if you could simulate all that,

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you'd only have one piece of the puzzle.

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These folks aren't the first to do this.

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"Lavarand" was patented by a company called
Silicon Graphics in 1996,

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but that only lasted a couple of years.

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Now of course, there are less flashy and

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more practical ways to
generate random numbers,

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but then I wouldn't be here.

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I would be at some
other company who'd gone and,

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I don't know, pointed a camera at
a basket of kittens.

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That'd be a bit higher
maintenance, though.