Remote key establishment by random mode mixing in multimode fibers and optical reciprocity

Yaron Bromberg*, Brandon Redding, Sebastien M. Popoff, Ningbo Zhao, Guifang Li, Hui Cao

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

22 Scopus citations


Disorder and scattering in photonic systems have long been considered a nuisance that should be circumvented. Recently, disorder has been harnessed for a rapidly growing number of applications, including imaging, sensing, and spectroscopy. The chaotic dynamics and extreme sensitivity to external perturbations make random media particularly well-suited for optical cryptography. However, using random media for distribution of secret keys between remote users still remains challenging since it requires the users have access to the same scattering sample. Here, we utilize random mode mixing in long multimode fibers to generate and distribute keys simultaneously. Fast fluctuations in fiber mode mixing provide the source of randomness for key generation, and optical reciprocity guarantees that the keys at the two ends of the fiber are identical. We experimentally demonstrate the scheme using classical light and off-the-shelf components, opening the door for a practically secure key establishment at the physical layer of fiber-optic networks.

Original languageAmerican English
Article number016105
JournalOptical Engineering
Issue number1
StatePublished - 1 Jan 2019

Bibliographical note

Publisher Copyright:
© 2019 The Authors.


  • fiber optics
  • key distribution
  • optical communications
  • optical cryptography
  • random media
  • reciprocity


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