If you’re driving through Britain, you might see giant concrete blocks with concave openings. What are they? Acoustic mirrors. More than 100 years ago, these mirrors were built along the coast of England, with the intention of using them to detect the sound of approaching German zeppelins. Invented by William Sansome Tucker, and operated at differing scales between around 1915 and 1935, the acoustic mirrors were able to signal an aircraft from up to 24 kilometers away, giving enough time to allow British defence to prepare for counterattack. The concave structures responded to sound by focusing the waves to a single point, where a microphone was positioned. Not only were they able to announce the arrival of an aircraft, but they could also determine the direction of attack of the plane to an accuracy of 1.5 degrees. Their development continued until the mid-1930s, when the invention of radar made them obsolete.
This internet service provider’s security keys are generated by a wall of lava lamps
You might think that the best security keys would be generated by computers, but in the case of CloudFlare, which caches and distributes data for thousands of large companies, you would only be half right. Computers, being logical devices, struggle with generating randomness, so CloudFlare uses real objects to generate “entropy,” which in cryptography means unpredictability. Encryption keys need to be unpredictable, or else an attacker can try to detect patterns. That’s where lava lamps come in, because they’re an inherently random variable. CloudFlare has two other randomness generators that are being built: The first, in the company’s London office, is known as the “Chaotic Pendulums,” and features giant grandfather-clock style pendulums, and the second, under construction in the company’s Austin office, is called “Suspended Rainbows.” Entropy is generated via patterns of light that are projected on walls, the ceiling, and the floor.
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