Cassandra is only carbon now2d ago

Gather 'round classical friends and semiquantum adversaries, it's story fucking time.

You may have heard of this fun new thing called "quantum key distribution" that uses the laws of physics to guarantee secure, unbreakable encryption. The first demonstration of QKD, known as "BB84" after its authors and the fact that it was built in 1984, had a bit of a problem, though. Sure, it was unbreakable but the mirrors used to send bits made different sounds based on whether they were sending a 0 or 1.

Show threadCassandra is only carbon now2d ago

So you didn't need to "break" BB84, you just needed to sit there with a microphone and you could read out the whole key. It doesn't matter how much physics guarantees the safety of your encryption if you go and tell the adversary what your key is.

For BB84, that deeply did not matter, it was a proof of principle. But in the 41 years since, that problem — that side channels exist — keeps getting forgotten.

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@xgranade evergreen
Mar 25 at 9:45pmWeb