Cloudflare and the lava lamps (LavaRand)

In short: Cloudflare uses a wall of lava lamps in its San Francisco office as an additional source of randomness. A camera films the lamps and the chaotic images are turned into random data.

In more detail: The system is called LavaRand. The lamps’ images are physically chaotic (heat, fluid movement, light). Bits are extracted from the camera images and mixed as additional entropy into the servers’ random generators. Other locations work similarly with other sources, for example a double pendulum in London and a radioactive decay detector in Singapore.

In detail

• Purpose: randomness for cryptographic keys, TLS connections and tokens. Many servers need many unpredictable bits.
• Important: the lamps are a supplement. In addition the processors’ hardware random generators and the operating system provide entropy. Several sources are mixed so that failure or manipulation of one source is not enough.
• Why physical? Calculation rules are predictable in principle, nature is not. That gives independent, hard-to-manipulate extra entropy.
• Public randomness: with the “League of Entropy” initiative there is a service for publicly verifiable randomness (drand).
• Comparison: lava lamps are not “better” than a good CSPRNG, they raise security through a variety of sources.

See also: Cloudflare, Random numbers: pseudo-random and true random