Researchers find hole in quantum cryptography that reveals the key

A team of researchers at Linkoping University and Stockholm University discovered a security vulnerability that compromises the integrity of quantum cryptography technologies.

In a study reported in the research journal Science Advances, the team found that by replacing the photon source that is used to create a quantum cryptography key with a traditional light source, attackers can identify the key and crack the encryption code.

Jan-Ake Larsson, a professor at Linkoping University's Division of Information Coding, and doctoral student Jonathan Jogenfors, demonstrated that an attack could compromise the cryptographic system while remaining undetected by Bell test experiments. The security test demonstrated a 97.6 percent faked detector efficiency, according to the research paper.

“With this security hole, it's possible to eavesdrop on traffic without being detected,” Jan-Ake Larsson told Linkoping University's research magazine. “We discovered this in our theoretical calculations, and our colleagues in Stockholm were subsequently able to demonstrate it experimentally.”