We prove the unconditional security of coherent-state-based differential phase shift quantum key distribution protocol (DPSQKD) with block-wise phase randomization. Our proof is based on the conversion of DPSQKD to an equivalent entanglement-distillation protocol where the estimated phase error rate determines the amount of the privacy amplification. The generated final key has a contribution from events where the sender emits two or more photons, indicating the robustness of DPSQKD against photon-number-splitting attacks.
@article{arxiv.1208.1995,
title = {Unconditional security of coherent-state-based differential phase shift quantum key distribution protocol with block-wise phase randomization},
author = {Kiyoshi Tamaki and Masato Koashi and Go Kato},
journal= {arXiv preprint arXiv:1208.1995},
year = {2012}
}