Encryption method for key exchange enables tap-proof communication to fend off future quantum tech threats

Quantum computers are a specter for future data security because they might break many of today’s encryption methods. Among other things, this will affect encrypted emails, messenger services, or online banking. Together with partners, researchers from Karlsruhe Institute of Technology (KIT) have developed a method that can reliably protect today’s Internet communication from tomorrow’s quantum technology threats.

The problem is that “the rapid progress in the development of quantum computers is a threat to data security and encrypted communication,” says Laurent Schmalen, Professor at KIT’s Communications Engineering Lab. “This is because the usual encryption methods are based on the fact that it is extremely difficult to break down large numbers into their prime factors, i.e., numbers that can only be divided by one and themselves.”

The expert explains that this process is extremely cumbersome and time-consuming for conventional computers, but not for quantum computers. “And once you know the prime factors of a large number, you can break the encryption.”

Traditional methods protect against future attacks

It is nevertheless possible to fend off quantum attacks with traditional cryptography—by using symmetric encryption. To do so, both sides need to exchange a virtual key before establishing the encrypted connection so that the transmitted data can be decrypted later on. This is a tap-proof method, but so far, it requires complex and expensive equipment.

The new method, however, works exclusively with conventional hardware. “We were able to perform the quantum key exchange with standard hardware as used in fiber-optic communication, such as the fiber-optic connections in homes and apartments, instead of relying on expensive special equipment,” says Schmalen. On this basis, universal use of the technology should be possible within five years. “This way, we can make the global telecommunications network tap-proof.”

Successful demonstration

The project team recently demonstrated the process in real time at the LMU Munich. A video transmission protected by the quantum key exchange was realized via an optical fiber connection on the campus. For this purpose, the KIT researchers developed innovative key matching algorithms. These ensure that both sides who want to establish an encrypted connection have an identical key, while the connection is still tap-proof.

“Our new algorithms for key matching are a decisive step towards ensuring tap-proof communication. They adapt dynamically to changing conditions and prevent attackers from obtaining information from the key exchange,” explains Schmalen.

Tobias Fehenberger, R&D Director at ADVA Network Security, adds, “Our project is a significant milestone in the development of quantum-safe encryption. The successful validation of a modular, high-performance system proves that quantum security based on commercially available components and an open architecture is ready for use in practice.”