Researchers demonstrate a method of adding truly random quantum noise to a microwave multilevel signal for quantum encryption applications.
Due to its inherently unavoidable nature, the addition of quantum noise is an ideal way to mask data for secrecy. Though artificial random noise has been demonstrated as an effective encryption method, it is not truly random and therefore insufficient for blocking the transmission interception of secure data.
Ken Tanizawa and Fumio Futami, from Tamagawa University, Japan, propose a cipher system for quantum noise encryption and decryption applications. Tanizawa will present their technique at the Optical Fiber Communication Conference and Exhibition (OFC), to be held 8-12 March 2020 at the San Diego Convention Center, California, U.S.A.
"Our previous work showed that quantum noise masking was effective to achieve secrecy in optical fiber communication. However, as the microwave frequency is three to five orders of magnitude lower than the optical frequency, the quantum noise masking effect at the microwave frequency is too small to achieve enough secrecy in wireless communications," Tanizawa said. "We propose utilizing microwave photonics or optical heterodyne to bridge this gap."
Caption: Schematic demonstration of the quantum noise encryption mechanism.
Credit: K. Tanizawa and F. Futami, Tamagawa University, Japan
In their proposed method, a multilevel optical signal is generated using a seed key, which is then shifted to a target microwave frequency. When light from a local oscillator is mixed into the multilevel signal, quantum noise is naturally added to a simultaneous detection of the system, creating a level of secrecy by masking the microwave multilevel signal.
Using a seed key shared ahead of time, a legitimate receiver can retrieve the original data. Without the key, a potential eavesdropper cannot accurately measure the transmission.
"Randomness is very important for higher security of the cipher, because eavesdroppers seek a statistical weakness for cryptanalysis," said Tanizawa. "Quantum noise is theoretically proven to be truly random."
Tanizawa and Futami tested their method on plain text data two ways: by transmitting the amplified cipher over a short radio frequency cable, and through a wireless link. In both tests, encryption and decryption were shown to achievable with good signal quality and security against signal interception.
"Our cipher system is robust and workable in the real world," said Tanizawa.
The researchers note their method can be used to handle sensitive data, which will become an even larger issue as wireless communications become more and more ubiquitous.
"In the era of 5G and 6G, we believe that many new applications will appear, and that security will be increasingly important," Tanizawa said.
These results and additional research will be presented onsite at OFC 2020.
