In July 2022, a pair of mathematicians in Belgium startled the cybersecurity world. They took a data-encryption scheme that had been designed to withstand attacks from quantum computers so sophisticated they don’t yet exist, and broke it in 10 minutes using a nine-year-old, non-quantum PC.

“I think I was more surprised than most,” says Thomas Decru, a mathematical cryptographer, who worked on the attack while carrying out postdoctoral research at the Catholic University of Leuven (KU Leuven) in Belgium. He and his PhD supervisor Wouter Castryck had sketched out the mathematics of the approach on a whiteboard, but Decru hadn’t been sure it would work — until the pair actually ran it on a PC. “It took a while for me to let it sink in: ‘Okay, it’s broken.’”

The encryption scheme, dubbed SIKE, was designed for the ambitious purpose of keeping secrets secret. It was one of four finalists chosen in 2022 for potential adoption by the US National Institute of Standards and Technology (NIST) in its Post-Quantum Cryptography standardization process. The aim is to find algorithms that can safeguard private information from the looming threat of quantum computers