Quantum cryptography is widely considered to be one of the most secure methods of communication, as the cryptography is alleged to be unbreakable.
Researchers at the University of Toronto appear to have contradicted that myth, however. Feihu Xu, Bing Qi and Hoi-Kwong Lo claim to have successfully broken a commercial quantum cryptography system developed by ID Quantique. This is the first successful attempt to break a quantum cryptography system.
The researchers relied on exploiting errors within the system.
“Unconditional security proofs of various quantum key distribution (QKD) protocols are built on idealized assumptions,” the researchers write. “One key assumption is: the sender (Alice) can prepare the required quantum states without errors. However, such an assumption may be violated in a practical QKD system. In this paper, we experimentally demonstrate a technically feasible “intercept-and-resend” attack that exploits such a security loophole in a commercial “plug & play” QKD system.”
You can read more about the research here