Testing the efficiency of a quantum encryption system against malicious attacks
Μιχαήλ Δ. Καρποντίνης
Abstract
The present thesis aimed to evaluate the efficiency and resilience of quantum cryptographic systems against malicious attacks, with emphasis on Quantum Key Distribution (QKD).Initially, fundamental concepts of quantum computing and quantum inform ation were examined, such as qubits, superposition, entanglement, decoherence and quantum gates, in order to establish the necessary theoretical background for the reader.Subsequently, key QKD protocols, such as BB84, E91, B92, BBM92 and Decoy-State techniques, were analyzed and compared in terms of security, practical applicability, and sensitivity to different categories of attacks.The methodology of the thesis was based on bibliographic and comparative analysis, using evaluation metrics such as Quantum Bit Error Rate (QBER), secret key generation rate, throughput, transmission distance, and channel losses.The analysis showed that simple theoretical attacks, such as intercept-resend, are usually more easily detectable due to an increase in QBER, whereas practical implementation attacks, such as detector blinding, time-shift, trojan-horse and photon-number-splitting attacks, can be more dangerous because they exploit device imperfections and do not always cause an obvious increase in errors.In conclusion, the theoretical security of QKD protocols is strong; however, their actual efficiency depends on the quality of implementation, technological limitations and the balance between protection and the final rate of secure key generation.