Fig. 2: Long-range quantum key exchange with an untrusted satellite.
From: Long-range QKD without trusted nodes is not possible with current technology
In the ARQ19 patent, the processing of the keys is only partly done through the public discussion channels with the satellite. The final processing is done directly between Bob and Carol (full arrow). However, if the satellite is untrusted, the data from the satellite can leak to an eavesdropper on the ground (dashed line). The discussion channel between Bob and Carol therefore must be protected from the eavesdropper. It must be a confidential channel.
