Security bounds for efficient decoy-state quantum key distribution

TL;DR

This paper reviews and generalizes the security bounds of the efficient decoy-state BB84 quantum key distribution protocol, demonstrating its robustness against general eavesdropping attacks while maintaining high key rates.

Contribution

It introduces a rigorous security proof against general attacks using a hypergeometric distribution bound, extending the protocol's applicability.

Findings

Security bounds are generalized to cover all attack types.

Key rate remains high, only slightly reduced under the new security model.

The protocol's practical performance is preserved despite theoretical extensions.

Abstract

Information-theoretical security of quantum key distribution (QKD) has been convincingly proven in recent years and remarkable experiments have shown the potential of QKD for real world applications. Due to its unique capability of combining high key rate and security in a realistic finite-size scenario, the efficient version of the BB84 QKD protocol endowed with decoy states has been subject of intensive research. Its recent experimental implementation finally demonstrated a secure key rate beyond 1 Mbps over a 50 km optical fiber. However the achieved rate holds under the restrictive assumption that the eavesdropper performs collective attacks. Here, we review the protocol and generalize its security. We exploit a map by Ahrens to rigorously upper bound the Hypergeometric distribution resulting from a general eavesdropping. Despite the extended applicability of the new protocol, its key rate is only marginally smaller than its predecessor in all cases of practical interest.