Quantum cryptography : security analysis and computer simulation of the two most common protocols

Abstract

Im Zuge dieser Diplomarbeit untersuchte ich die Sicherheit der BB84 und BBM92 Quantenkryptografie-Protkolle gegenüber Einzelattacken und Photon Number Splitting Attacken in realistischen Szenarien. Nach der Herleitung von den theoretischen Grundlagen wurden verschiedene Quantenkryptografie-Experimente mittels eines eigens entwickelten MATLAB-Programm untersucht. Es wurde ein Vergleich verschiedener Szenarien, u.a. die Verwendung von Decoy States oder auch eines asymmetrisches BBM92 Aufbaus, durchgeführt.<br />

In this diploma thesis I investigate the security of the BB84 and BBM92 quantum cryptography protocols in realistic setups against individual and photon number splitting attacks. After developing the theoretical basis, we simulate the security of various quantum cryptography experiments in a self-developed MATLAB program. It is shown in the course of this thesis that so-called decoy states vastly improve the performance of the BB84 protocol. A BB84 protocol with PDC source and decoy states is able to match an asymmetric BBM92 setup in transmission distance, while having a higher gain. It is also shown that for a symmetric BBM92 setup quantum cryptography becomes feasible over longer distances compared to its BB84 PDC counterpart. Moreover, the thesis investigates for the first time the consequences of performing a realistic error correction, compared to interpolated error correction implementations in prior works.