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Dr. Laszlo Kish
Dr. Laszlo Kish is the director of research for the Fluctuation and Noise Exploitation Laboratory. | Image: Dr. Laszlo Kish

Dr. Laszlo Kish, professor in the Department of Electrical and Computer Engineering at Texas A&M University, has solved a long-standing open problem related to the Kirchhoff-law-Johnson-noise (KLJN) key exchange and the security it provides. In the KLJN exchange, communication is established and explained through two parties — ‘Alice’ and ‘Bob’. ‘Eve’ is the name given to an eavesdropper, or one with malicious intent that is actively trying to breach security and obtain sensitive information during the transmission of secure information from ‘Alice’ to ‘Bob’ or vice versa.

One way that an ‘Eve’ can gain access to this sensitive information is through a special class of active attacks that utilizes the adjustment of time in the clocks within the hardware system. By opening this door into the hardware, ‘Eve’ is then able to make more advanced attacks on the system.

On May 4, 2022, President Joe Biden signed a National Security Memorandum that promotes the research and development of quantum-resistant cryptography. Unconditional security belongs to this class of security. An essential component of such a system is a secure key exchange protocol that requires a hardware solution where the laws of physics guarantee privacy against passive, or listening, attacks of ‘Eve.’

The KLJN key exchange system offers unconditional security by using classical statistical physics and the Second Law of Thermodynamics, while quantum key distribution uses quantum physics and the Quantum No-Cloning Theorem. Unfortunately, both protocols are potentially vulnerable to active attacks where ‘Eve’ takes over the control of the clocks of the communicating parties, ‘Alice’ and ‘Bob.’

Kish’s paper on this topic, titled “Time Synchronization Protocol for the KLJN Secure Key Exchange Scheme,” proposes a general defense against clock attacks in the KLJN system and will come out in the October issue of Fluctuation and Noise Letters. The preprint of the paper is currently available.