Tripartite Layered Quantum Key Distribution Scheme with a Symmetrical Key Structure

Asymmetric entanglement could provide a crucial layered key structure for quantum cryptography. A new symmetrical tripartite quantum key distribution scheme based on the simplest layered quantum key distribution (L-QKD) model is devised. With an interesting rotational symmetrical key distribution scheme, the proposed tripartite QKD protocol could establish a more integrated key system, which expands the number of conference keys for secure broadcast and distribute layered secret keys among any legitimate participants simultaneously. The proposed scheme is more flexible, robust and efficient to guarantee the fairness among communication parties than the original L-QKD protocol, and our scheme also could be applied to encryption in the butterfly network precisely. Moreover, based on three asymmetric (4, 4, 2) entangled state, a novel symmetric (4, 4, 4) entangled state to implement L-QKD scheme is discussed. Finally, the security of L-QKD scheme is analyzed via information-theoretic proof.