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Christiana Chamon and Dr. Lazslo Kish
Christiana Chamon is working with Dr. Laszlo Kish on a project to provide unconditional security for sensitive data and information. | Image: Texas A&M Engineering, Specialties Photography

More than 98.2 million individuals were impacted by 10 of the biggest data breaches in the first half of 2021, according to the Identity Theft Resource Center and the U.S. Department of Health and Human Services. Keeping sensitive data (social security numbers, banking information, etc.) secure is paramount and one way to achieve this is through the use of the Kirchhoff-Law-Johnson-Noise (KLJN) key exchange system, which provides unconditional security for the key exchange, similar to quantum encryption.

Christiana Chamon, a doctoral student in the Department of Electrical and Computer Engineering at Texas A&M University, is working with faculty advisor Dr. Laszlo Kish to push the boundaries of what is accepted and known for the KLJN key exchange and provide further support for how to maintain the system’s highest security level possible.

Their findings were published as a high-profile "Perspective" article in Applied Physics Letters by AIP Publishing in July 2021.

The focus topic of their current work is on the thermodynamical state of the KLJN system. In KLJN exchange, communication is established and explained through two parties — ‘Alice’ and ‘Bob.’ At both ends of the communication line between these two parties, there is an identical pair of resistors with lower and higher values.

“The foundation of the perfect security in the KLJN scheme is thermal equilibrium and the second law of thermodynamics,” Kish said. “In other words, it is impossible to crack the security of the ideal KLJN protocol.”

In all previous works, the proposed KLJN schemes required thermal equilibrium between ‘Alice’ and ‘Bob’ to achieve perfect security, meaning both pairs of resistors remained at the same temperature. However, recent developments by researchers published in Nature Science Reports showed a modified scheme, which offered an arbitrary choice of the resistor values by ‘Alice’ and ‘Bob’.

A serious implication of this situation is that the temperatures of the resistors are then typically different, which indicates an out-of-equilibrium situation. Thermal equilibrium was thought as the foundation of the perfect security of the KLJN protocol. Thus, this foundation had been challenged.  

However, Chamon and Kish disproved this challenge by introducing a surprising attack against this non-equilibrium protocol. By sampling the voltage data at the moments of zero crossings of the current data, they showed a significant information leak toward the eavesdropper. As soon as the thermal equilibrium is restored, the system becomes perfectly secure again, confirming that perfect, unconditional security requires thermal equilibrium.

“This work is of fundamental importance because it provides new information that disproves what was originally accepted,” Chamon said. “Dogmas have no place in science.”