@misc{W1970006170,
  author = {Hoi-Kwong Lo and H. F. Chau},
  title = {Unconditional Security of Quantum Key Distribution over Arbitrarily Long Distances},
  year = {1999},
  howpublished = {Science},
  doi = {https://doi.org/10.1126/science.283.5410.2050}
}