Free space optical secret key agreement

Hiroyuki Endo, Mikio Fujiwara, Mitsuo Kitamura, Orie Tsuzuki, Toshiyuki Ito, Ryosuke Shimizu, Masahiro Takeoka, Masahide Sasaki

Research output: Contribution to journalArticlepeer-review

15 Citations (Scopus)


Free space optical (FSO) communications are enabling high-speed global wireless networks. Thanks to the highly directional nature of laser beam, they also yield a greater security advantage over radio frequency counterparts. When combined with a scheme of secret key agreement (SKA), FSO-SKA can establish at high speed a symmetric secret key which cannot be decrypted even by unbounded computer resources. Although there have been many theoretical studies on SKA, experimental investigations have been quite lacking, especially on quantifying eavesdropping risks and secret key rates in realistic environment. Here, we report the first full-field implementations of FSO-SKA in a 7.8-km terrestrial link with a probing station, enabling the estimation of eavesdropping risks. We attain the final key rates from 100 kbps to 7.77 Mbps under various atmospheric and beaming conditions even with total losses of 55dB or higher, in which known quantum key distribution schemes attain impractically low key rates.

Original languageEnglish
Pages (from-to)23305-23332
Number of pages28
JournalOptics Express
Issue number18
Publication statusPublished - 2018 Sept 3
Externally publishedYes

ASJC Scopus subject areas

  • Atomic and Molecular Physics, and Optics


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