Quantum computer challenges encryption

This article is excerpted from Science et Avenir monthly, issue 902, April 2022.

Hundreds, thousands, even millions of years… This is the time required for the most powerful supercomputers to “break” current encryption protocols. These messages secure our messages, bank accounts, medical data, etc. They are based on arithmetic operations, such as the decomposition of very large numbers into primes (they are only divisible by 1 and themselves). However, the Schur algorithm, invented in 1994 by the American mathematician Peter Schur, makes it possible to exploit the unique properties of quantum mechanics such as superposition to perform these operations in record time. Goodbye secrecy? Not yet, fortunately.

Current quantum computer prototypes lack the ability to efficiently run such algorithms: they would need thousands of qubits or more to become a threat. But labs and companies would prefer to prepare for the public appearance of such a machine…especially since another major problem emerges: data that is secure today may not be secure tomorrow. In fact, if the hacker who saved this data today gets a quantum computer in the future, he’ll be able to decrypt it later. Therefore, it is a real threat to data that we would like to be confidential in the long run (trade agreements, state secrets, etc.). Another reason to switch to “quantum-resistant” encryption.

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