The Security Analysis of Continuous-Variable Quantum Key Distribution under Limited Eavesdropping with Practical Fiber
arxiv(2023)
摘要
Research on optimal eavesdropping models under practical conditions will help
to evaluate realistic risk when employing quantum key distribution (QKD) system
for secure information transmission. Intuitively, fiber loss will lead to the
optical energy leaking to the environment, rather than harvested by the
eavesdropper, which also limits the eavesdropping ability while improving the
QKD system performance in practical use. However, defining the optimal
eavesdropping model in the presence of lossy fiber is difficult because the
channel is beyond the control of legitimate partners and the leaked signal is
undetectable. Here we investigate how the fiber loss influences the
eavesdropping ability based on a teleportation-based collective attack model
which requires two distant stations and a shared entanglement source. We find
that if the distributed entanglement is limited due to the practical loss, the
optimal attack occurs when the two teleportation stations are merged to one and
placed close to the transmitter site, which performs similar to the
entangling-cloning attack but with a reduced wiretapping ratio. Assuming Eve
uses the best available hollow-core fiber, the secret key rate in the practical
environment can be 20
the entanglement distillation technology is mature enough to provide high
quality of distributed entanglement, the two teleportation stations should be
distantly separated for better eavesdropping performance, where the
eavesdropping can even approach the optimal collective attack. Under the
current level of entanglement purification technology, the unavoidable fiber
loss can still greatly limit the eavesdropping ability as well as enhance the
secret key rate and transmission distance of the realistic system, which
promotes the development of QKD systems in practical application scenarios.
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