TORONTO, March 30, 2012 /CNW/ - A research team led by University of
Toronto Professor Hoi-Kwong Lo has found a new quantum encryption method to foil even the most
sophisticated hackers. The discovery is outlined in the latest issue of
Physical Review Letters.
Quantum cryptography is, in principle, a foolproof way to prevent
hacking. It ensures that any attempt by an eavesdropper to read encoded
communication data will lead to disturbances that can be detected by
the legitimate users. Therefore, quantum cryptography allows the
transmission of an unconditionally secure encryption key between two
users, "Alice" and "Bob," in the presence of a potential hacker, "Eve."
The encryption key is communicated using light signals and is received
using photon detectors. The challenge is that Eve can intercept and
manipulate these signals.
"Photon detectors have turned out to be an Achilles' heel for quantum
key distribution (QKD), inadvertently opening the door to subtle
side-channel attacks, most famously quantum hacking," wrote Dr. Charles
Bennett, a research fellow at IBM and the co-inventor of quantum
When quantum hacking occurs, light signals subvert the photon detectors,
causing them to only see the photons that Eve wants Bob to see. Indeed,
earlier research results by Professor Lo and independent work by Dr.
Vadim Makarov of the Norwegian University of Science and Technology
have shown how a clever quantum hacker can hack commercial QKD systems.
Now, Professor Lo and his team have come up with a simple solution to
the untrusted device problem. Their method is called "Measurement
Device Independent QKD." While Eve may operate the photon detectors and
broadcast measurement results, Bob and Alice no longer have to trust
those measurement results. Instead, Bob and Alice can simply verify
Eve's honesty by measuring and comparing their own data. The aim is to
detect subtle changes that occur when quantum data is manipulated by a
Specifically, in Measurement Device Independent QKD, the two users send
their signals to an untrusted relay - "Charlie" - who might possibly be
controlled by Eve. Charlie performs a joint measurement on the signals,
providing another point of comparison.
"A surprising feature is that Charlie's detectors can be arbitrarily
flawed without compromising security," says Professor Lo. "This is
because, provided that Alice and Bob's signal preparation processes are
correct, they can verify whether Charlie or Eve is trustworthy through
the correlations in their own data following any interaction with
A proof-of-concept measurement has already been performed. Professor Lo
and his team are now developing a prototype measurement device
independent QKD system, which they expect will be ready within five
As a result of implementing this new method, quantum cryptography's
Achilles' heel in the fight against hackers has been resolved. Perhaps,
a quantum jump in data security has now been achieved.
Professor Lo is a faculty member in The Edward S. Rogers Sr. Department
of Electrical & Computer Engineering and the Department of Physics. His
team includes Senior Research Associate Dr. Bing Qi, who is based in
Professor Lo's laboratory, and Professor Marcos Curty of the University
of Vigo in Spain.
To obtain a copy of the paper, please visit:
SOURCE University of Toronto - Engineering Strategic Communications
For further information:
Professor Hoi-Kwong Lo
The Edward S. Rogers Sr. Department of Electrical & Computer Engineering
and the Department of Physics
University of Toronto
Communications & Media Relations Strategist
Faculty of Applied Science & Engineering
University of Toronto