Quantum computer challenges cryptography

This article is taken from the monthly journal Sciences et Avenir – La Recherche #902 of April 2022.

Hundreds, thousands, even millions of years… That is how long it takes for the most powerful supercomputers to “break” the existing encryption protocols. They protect our messages, bank accounts, medical data, etc. They are based on mathematical operations such as factoring very large numbers into prime numbers (divisible only by 1 and themselves). However, Shor’s algorithm, invented in 1994 by American mathematician Peter Shor, makes it possible to use the unique properties of quantum mechanics, such as superposition, to perform these operations in record time. Goodbye privacy? Fortunately, not yet.

Current prototype quantum computers lack the power to run such algorithms efficiently: they would need thousands of qubits or more to become a threat. But labs and companies are choosing to prepare for the announced arrival of such a machine… all the more so as another serious problem arises: data that is currently secure may no longer be secure tomorrow. Indeed, if the pirate who saved this data today acquired a quantum computer in the future, he would be able to decipher it a posteriori. Thus, this is a real threat to data that we would like to keep private in the long run (trade agreements, state secrets, etc.). Another reason to switch to “quantum-resistant” cryptography.

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