Quantum-Only Key Distribution

Based on the principles of quantum physics, Quantum key distribution (QKD) is theoretically unbreakable. However, the use of classical channels in conventional QKD protocols introduces vulnerabilities in practice. In this research, we propose a new QKD protocol that uses only the quantum channel. It eliminates the classical channel to minimize risks. While random bases are used for initial key distribution, a pre-shared secret is used to create bases for key sifting and error estimation. We hypothesized that the proposed protocol would exhibit higher error rates and lower exposure rates than the benchmark BB84 protocol. We simulated the protocol and compared it to the BB84 protocol in four scenarios. The simulation results show that the new protocol produces an error rate of approximately 0.5, nearly twice that of the BB84 protocol. The high error rates allow the communicating parties to more effectively detect intercept-resend and man-in-the-middle attacks. Moreover, the new protocol exhibits a key bit exposure rate of approximately 0.5, implying that an attacker would gain minimal advantage beyond randomly guessing. It also indicates that privacy amplification may become unnecessary. This security feature applies not only to intercept-resend and man-in-the-middle attacks but also to photon-number-splitting attacks. Overall, the results support our hypothesis, suggesting that the proposed protocol would enable communicating parties to detect attacks and protect privacy more effectively.