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Hidden Multidimensional Modulation Side Channels in Quantum Protocols

Quantum protocols such as quantum key distribution (QKD) and blind quantum computing allow for information-theoretic, quantum-safe security . Thanks to measurement-device-independent QKD (MDI QKD), all side channels on the detection end can be completely eliminated . Therefore, the source, as well as device-independent (DI) QKD are the last frontiers of investigation for security, with DI QKD remaining impractical due to its demanding requirements, such as near-perfect detector efficiencies.
Normalized temporal phase profiles used in the key rate analysis

Publication Date: March 31, 2025

Authors:

Amita Gnanapandithan, Li Qian, and Hoi-Kwong Lo

Abstract:

Quantum protocols including quantum key distribution and blind quantum computing often require the preparation of quantum states of known dimensions. Here, we show that, rather surprisingly, hidden multidimensional modulation is often performed by practical devices. This violates the dimensional assumption in quantum protocols, thus creating side channels and security loopholes. Our work has important impacts on the security of quantum cryptographic protocols.

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