Trusted and entrusted nodes for QKD
There was an research paper in Nature using a satellite as an untrusted node in quantum key distribution. This has been demonstrated. While it's only 2 trusted nodes in the paper it's easy to see how it can be expanded.
Yin, J., Li, Y., Liao, S. et al. Entanglement-based secure quantum cryptography over 1,120 kilometres. Nature 582, 501–505 (2020).