Quantum Key Distribution - Quantum Hacking

Quantum Hacking

Hacking attacks target vulnerabilities in the operation of a QKD protocol or deficiencies in the components of the physical devices used in construction of the QKD system. If the equipment used in quantum key distribution can be tampered with, it could be made to generate keys that were not secure using a random number generator attack. Another common class of attacks is the Trojan horse attack which does not require physical access to the endpoints: rather than attempt to read Alice and Bob's single photons, Eve sends a large pulse of light back to Alice in between transmitted photons. Alice's equipment reflects some of Eve's light, revealing the state of Alice's basis (e.g., a polarizer). This attack can be detected, e.g. by using a classical detector to check the non-legitimate signals (i.e. light from Eve) entering Alice's system. It is also conjectured that most hacking attacks can similarly be defeated by modifying the implementation, though there is no formal proof.

Several other attacks including faked-state attacks, phase remapping attacks and time-shift attacks. are now known. The time-shift attack has even been demonstrated on a commercial quantum cryptosystem. This is the first demonstration of quantum hacking against a non-homemade quantum key distribution system. Later on, the phase-remapping attack was also demonstrated on a commercial QKD system (made and sold by the Swiss company Id Quantique). It is one of the first ‘intercept-and-resend’ attacks on top of a widely used QKD implementation in commercial QKD systems. This work has been widely reported in media.

The first attack that claimed to be able to eavesdrop the whole key without leaving any trace was demonstrated in 2010. It was experimentally shown that the single-photon detectors in two commercial devices could be fully remote-controlled using specially tailored bright illumination. In a spree of publications thereafter, the collaboration between the Norwegian University of Science and Technology in Norway and Max Planck Institute for the Science of Light in Germany, has now demonstrated several methods to successfully eavesdrop on commercial QKD systems based on weaknesses of Avalanche photodiodes (APDs) operating in gated mode. This has sparked research on new approaches to securing communications networks.