The nature of quantum mechanics provides us with an opportunity to statistically detect eavesdropping in quantum key distribution (QKD) protocols, which is unimaginable in classical digital communications. By utilizing Hoeffding's inequality, this study analyzes the upper bounds of the false-positive ratio (FPR) and false-negative ratio (FNR) of eavesdropping detection in the Bennett-Brassard-84 (BB84) QKD protocol, where eavesdropping is detected if the measured quantum bit error rate (QBER) is equal to or higher than a threshold. The analysis clarifies the trade-off between the accuracy of eavesdropping detection and the economy of quantum resources in the BB84 protocol. Owing to the central limit theorem, the QBER measured by 300 quantum bits (qubits) is sufficient to guarantee lower than 0.009% of the FPR and FNR of eavesdropping detection. To deal with rapidly varying quantum channel conditions, this study further introduces grouped BB84 protocol and combinatory eavesdropping detection algorithms. A polarization basis is changeable for a group of qubits, and eavesdropping is judged by a combination of criteria between QBER and group-QBER in the proposed protocol and algorithms. In our extensive simulation study, the grouped BB84 protocol with 300 qubits comparison guarantees at least 99.92% accuracy in eavesdropping detection under rapidly varying quantum channel conditions.

This paper explores the nature of scientific research traffic on the Korea research environment open network. Based on these investigations, we propose a scalable design and algorithm for the science demilitarization zone (DMZ). The proposed design allows users to share a data-transfer node (DTN), which is essential but costly equipment in the Science DMZ. The proposed iterative greedy algorithm attempts to minimize the peak traffic of the shared DTNs. By considering state-of-the-art DTN and practical research traffic, the proposed design and algorithm achieve up to 79% capital expenditure (CAPEX) reduction from that of a reference design of the Science DMZ where a DTN is allocated per user. The proposed algorithm achieves a 5-order-of-magnitude reduction in computation time at the cost of acceptable CAPEX overheads compared to those of the minimum-CAPEX solutions.

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