Free-space optical wiretap channel and experimental secret key agreement in 7.8 km terrestrial link

Mikio Fujiwara, Toshiyuki Ito, Mitsuo Kitamura, Hiroyuki Endo, Orie Tsuzuki, Morio Toyoshima, Hideki Takenaka, Yoshihisa Takayama, Ryosuke Shimizu, Masahiro Takeoka, Ryutaroh Matsumoto, Masahide Sasaki

Research output: Contribution to journalArticlepeer-review

22 Citations (Scopus)


Secret key agreement using physical properties of a wireless channel is becoming a promising scheme to establish a secret key between two users, especially in short-distance radio frequency (RF) communications. In this scheme, the existence of codes or key distillation that can make the leaked information to an eavesdropper arbitrarily small can be derived in an information theoretical way, given a priori knowledge on the channel linking a sender (Alice), a legitimate receiver (Bob), and an eavesdropper (Eve), which is called the wiretap channel. In practice, however, it is often difficult for Alice and Bob to get sufficient knowledge on Eve. In this study, we implement a free-space optical wiretap channel in a 7.8 km-terrestrial link and study how to estimate Eve’s tapping ability, demonstrating high speed secret key agreement in the optical domain under a certain restricted condition of line-of-sight.

Original languageEnglish
Pages (from-to)19513-19523
Number of pages11
JournalOptics Express
Issue number15
Publication statusPublished - 2018 Jul 23
Externally publishedYes

ASJC Scopus subject areas

  • Atomic and Molecular Physics, and Optics


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