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.
Cryptography in the modern era is very important to prevent a cyber attack, as the world tends to be more and more digitalized. Classical cryptographic protocols mainly depend on the mathematical complicacy of encoding functions and the shared key, like RSA protocol in which security depends upon the fact that factoring a big number is a hard problem to the current computers. This means that high computing power can help you crack traditional encryption methods. Quantum machines claim to have this kind of power in many instances. Factorization of big numbers may be possible with Shor's algorithm with quantum machines in considerable time. Apart from this, the main problem is key sharing i.e., how to securely share the key the first time to validate the encryption. Here comes quantum key distribution. Two parties who are interested in communication with each other, create a process, which claims considerable security against an eavesdropper, by encoding and decoding information in quantum states to construct and share a secret key. Quantum key distribution may be done in a variety of ways. This paper begins with experimental verification of the BB84 procedure utilizing four bases (using phase gates) followed by the experimental realization of the SARG04 protocol which was derived from BB84 Protocol to overcome PNS attack. The possibility of a third-party attack and the effect of noise is considered and implemented. The IBM Quantum Experience platform was used for all of the implementations.
In order to solve the low key distribution efficiency problem of the BB84 protocol, an improved BB84 quantum key distribution scheme is presented in this paper. Firstly the same polarization basis is used by the sender and the receiver with the consistent agreement. This process could make quantum key distribution rate higher. Then signature combined with the error correction method based on the odd and even parity is used to ensure the safety of the transmission. The analyses results indicate that the advantage of the improved scheme lies in that the all photons sent to Bob by Alice are useful. It can not only reduce the time extracting the original key, but also solve the authentication problem in the process of communication. The key distribution efficiency is two times of the original BB84 protocol improved scheme.