In theory, quantum physics can bypass the hard mathematical problems at the root of modern encryption. A new proof shows how.

Hard problems are usually not a welcome sight. But cryptographers love them. That’s because certain hard math problems underpin the security of modern encryption. Any clever trick for solving them will doom most forms of cryptography.

Several years ago, researchers found a radically new approach to encryption that lacks this potential weak spot. The approach exploits the peculiar features of quantum physics. But unlike earlier quantum encryption schemes, which only work for a few special tasks, the new approach can accomplish a much wider range of tasks. And it could work even if all the problems at the heart of ordinary “classical” cryptography turn out to be easily solvable.

But this striking discovery relied on unrealistic assumptions. The result was “more of a proof of concept,” said Fermi Ma, a cryptography researcher at the Simons Institute for the Theory of Computing in Berkeley, California. “It is not a statement about the real world.”

Now, a new paper by two cryptographers has laid out a path to quantum cryptography without those outlandish assumptions. “This paper is saying that if certain other conjectures are true, then quantum cryptography must exist,” Ma said.

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