分析 DPS 和 MDI 量子密鑰分發的性能差異與竊聽

Abstract

量子密鑰分發在當前的量子資訊加密中已被廣泛應用，基於量子力學的物理定律，使得通訊雙方可以無條件安全地獲得一組相同的隨機密鑰。然而，在實際應用中，由於光學元件的不完美和缺陷，可能導致密鑰生成效率下降，甚至使竊聽者能夠利用這些漏洞部分獲取密鑰資訊，從而將通訊暴露在危險中。 本論文旨在模擬研究差分相位移和獨立測量設備兩種協定。我們利用開發的模擬器分析不同元件參數的影響，包括脈衝重疊效應、相位調變失真對系統密鑰和錯誤率的影響，並探討通過調整偵測器開啟時間來優化系統的方法。接下來，我們將比較這兩種協定在密鑰生成效率上的差異，以及是否需要更高規格的儀器才能夠成功實施。我們還將分析獨立測量設備協定對比起差分相位移協定在實際上可能面臨的雙光子時間延遲和溫差對通訊的不利影響。 此外，我們使用竊聽模組評估兩種協定在竊聽者攻擊時的安全性，並得出在獨立測量設備協定中竊聽者攻擊所引起的錯誤率比差分相位移來的更高，且當竊聽者的攔截率以及偵測能力較高時，獨立測量設備協定的安全性較高，但其經過隱私放大後的安全密鑰產生效率比較低。最後則使用誘餌狀態的協定來討論此方式是否能成功揭露竊聽者的行為，並分析出此方式對於偵測竊聽者的能力極限。

Quantum key distribution (QKD) has been widely used in current quantum information encryption. Based on the physical laws of quantum mechanics, it allows communication parties to securely obtain a set of shared random keys. However, in practical applications, due to the imperfections and defects of optical devices, the key generation efficiency may decrease, and even eavesdroppers may be able to exploit these vulnerabilities to partially obtain key information, thus exposing the communication to danger. This paper aims to simulate and research two protocols: differential phase shift (DPS) and measurement-device-independent (MDI) QKD. We utilize our developed simulator to analyze the influence of different device parameters, including the pulse overlapping effect, and phase modulation distortion on the system key and error rate. We also explore methods to optimize system performance by adjusting the detector time window. Furthermore, we compare the efficiency of key generation between these two protocols and whether higher-specification devices are required for successful implementation. We will also analyze the advantages of biphotons time delay and temperature difference on communication in the MDI protocol compared to the DPS. In addition, we use the eavesdropping module to evaluate the security of the two protocols, and conclude that the error rate induced by eavesdropper attacks in the MDI protocol is higher than that in the DPS. When the eavesdropper's interception ratio and detection capability are high, the security of MDI protocol is higher, but its secure key generation efficiency after privacy amplification is relatively low. Finally, we use the decoy state protocol to discuss whether this method can successfully detect the eavesdropper's behavior, and analyze the limit of the eavesdropper detection capability of this method.