CAPTCHA-Based Secret-Key Sharing Using Quantum Communication

Digital communication has revolutionized the modern era, where two parties can communicate apart easily; but this also opens up opportunities for adversarial attacks. To guarantee a secure communication over such channels, there have been several approaches proposed based on secret-key distribution including the BB84 quantum secret-key sharing protocol. Although it is almost resistant to eavesdropping attacks, the BB84 protocol presents certain challenges. Specifically, it is vulnerable to impersonation attacks. Moreover, it is slow owing to the hit-and-trail method for secret-key distribution. Hence, in this article, we propose a secure and efficient protocol for secret-key sharing by combining image-based CAPTCHA and the classical BB84 protocol. We demonstrate that the proposed protocol is secure against impersonation attacks, including DDoS attacks, and it is at least twice as efficient as BB84 in terms of communicated qubits.