Physicists Developing Solutions to Keep Digital Information Safe at Sea

People have long looked for ways to guard personal and confidential information, especially with the advent of the digital age. And as long as information has been protected, people have been trying to crack the codes concealing it.

Three UT physicists are drawing on their expertise in quantum mechanics to help solve a twenty-first century problem: keeping digital information safe at sea.

The team has won a three-year, $1.1 million award from the Office of Naval Research for this work.

Associate Professor Bing Qi and Assistant Professor Raphael Pooser, both UT-Oak Ridge National Laboratory joint faculty, and Professor George Siopsis are working with colleagues from two other universities to develop solutions using modern-day cryptography to safeguard naval information.

Collaborators include Hoi-Kwong Lo of the University of Toronto, a leading expert in quantum information science, and Eric Chitambar of Southern Illinois University.

Currently, the vastness and turbulence of the sea make communication challenging because communication channels have higher loss and require networks to be highly reconfigurable. Building on the strengths of quantum key distribution, the team plans to develop a multifaceted and flexible network for the demands of the maritime environment.

Qi noted how far cryptography has come since the fifth century and how physics research and applications continually evolve to meet society’s needs.

“It’s amazing to me that by exploring the quantum nature of light, we can achieve mission impossible in classical physics, even with practical devices we use in an optical lab every day,” he said.

Coding a message has historically involved a sender encrypting information and the receiver translating the message by using a shared key—a string of secret bits. Quantum key distribution can provide uncrackable keys for modern-day cryptography. Data protected by the “quantum key” appear completely random so anyone who tries to intercept it won’t gain any useful information. The parties exchanging information have a shared secret key known only to them that they can use to encrypt and decode messages.

While quantum key distribution works well over optical fibers, the vastness and turbulence of the high seas present their own difficulties. The communication channels have a higher loss. Strong ambient light requires a sophisticated filtering scheme to selectively detect signal photons, and the movement of sea vessels requires the communication network to be highly reconfigurable.

To mitigate these obstacles, the research team has proposed a design with multiple options for key generation, including a measurement-device-independent quantum key distribution protocol. This protocol is flexible and provides for the multi-user network that is required in a sea environment. It offers high security in an untrusted scenario, while the more standard quantum key distribution protocol offers greater efficiency where any third parties involved are trusted and are privy to the secure key.

The team’s proposal contains a novel ingredient that could allow ships to use their geographical coordinates as the sole credential to establish an authenticated channel—an especially useful approach in ship-to-ship quantum key distribution.

“By allowing the system to be operated at different modes, we hope the proposed solution can be easily adapted to different applications,” Qi said.


Lola Alapo (865-974-3993,

Catherine Longmire (865-974-8950,