Free space optical secret key agreement.

Area of Science:

• Optics and Telecommunications
• Quantum Information Science
• Network Security

Background:

• Free Space Optical (FSO) communication offers high-speed wireless networking with inherent security advantages over radio frequencies.
• Secret Key Agreement (SKA) schemes, when combined with FSO, can establish high-speed symmetric secret keys resistant to even advanced decryption.
• Experimental validation of FSO-SKA, particularly in realistic environments for quantifying eavesdropping risks and key rates, has been limited.

Purpose of the Study:

• To report the first full-field experimental implementation of Free Space Optical Secret Key Agreement (FSO-SKA).
• To quantify eavesdropping risks and secret key rates in a realistic terrestrial FSO link.
• To demonstrate the feasibility of high-speed secret key generation in challenging environmental conditions.

Main Methods:

• Implementation of a 7.8-km terrestrial FSO link with a probing station for real-time monitoring.
• Full-field experimental setup to establish secure communication and secret key agreement.
• Measurement of secret key rates under diverse atmospheric and beaming conditions, including high signal loss.

Main Results:

• Achieved final secret key rates ranging from 100 kbps to 7.77 Mbps.
• Demonstrated successful FSO-SKA operation under various atmospheric and beaming conditions.
• Attained high key rates even with total losses exceeding 55dB, surpassing limitations of current quantum key distribution schemes.

Conclusions:

• The experimental implementation validates FSO-SKA as a viable method for high-speed, secure communication.
• FSO-SKA offers practical advantages in key generation rates compared to quantum key distribution in real-world scenarios.
• This work paves the way for secure, high-capacity global wireless networks using FSO technology.