Quantum Key Distribution: Principles, Applications and Limitations

Creative Commons License

Yılmazoğlu Y., Engin O.

International Student Congresses (Muisc 2026), İstanbul, Türkiye, 11 - 12 Mayıs 2026, ss.66-67, (Özet Bildiri)

  • Yayın Türü: Bildiri / Özet Bildiri
  • Basıldığı Şehir: İstanbul
  • Basıldığı Ülke: Türkiye
  • Sayfa Sayıları: ss.66-67
  • Açık Arşiv Koleksiyonu: AVESİS Açık Erişim Koleksiyonu
  • Marmara Üniversitesi Adresli: Evet

Özet

Quantum cryptography, unlike classical cryptography, is an innovative approach that bases secure communication on the principles of quantum mechanics instead of mathematical problems. Using quantum effects such as superposition, entanglement, and no-cloning; secret key generation, message authentication, and more advanced cryptographic operations can be performed. The most mature and widespread application in this field is Quantum Key Distribution (QKD), which enables the creation of a shared key between sender and receiver whose security is guaranteed by the laws of physics. In QKD systems, the communicators are traditionally referred to as sender "Alice" and the receiver "Bob" in the literature. Quantum bits (qubits) transmitted between these two parties are typically transferred using different polarization states of photons. The BB84 protocol, proposed in 1984, was the first quantum key distribution protocol and is based on the measurement of photons encoded in different bases. The E91 protocol, on the other hand, offers a quantum entanglement-based approach, enabling secure key generation via entangled particle pairs. These protocols are fundamental structures that define how quantum communication can be implemented and how security can be ensured. After message transmission, the parties analyze error rates by comparing some of their data over a classical communication channel and detect any potential eavesdropping attempts. Due to the tendency of quantum systems to decay during measurement, a third party monitoring the communication inevitably leads to errors in the system, which can be directly detected. Subsequently, error correction and privacy amplification processes are applied to obtain a secure key. This key is then used in conjunction with classical encryption algorithms; for example, Advanced Encryption Standard (AES) or one-time pad encryption methods are preferred for this purpose. The most important feature of quantum cryptography is that it provides information-theoretic security. This means that system security is independent of computing power and, under ideal conditions, cannot be broken by any attacker, including quantum computers. Furthermore, the ability to directly detect eavesdropping attempts provides a significant advantage, especially in critical communication infrastructures. Today, this technology is beginning to be applied in areas requiring high security, such as telecommunication networks, financial systems, military communications, 5G infrastructures, and satellite-based communication systems. Beyond QKD, quantum cryptography also encompasses more emerging applications such as quantum random number generation, quantum digital signatures, quantum currency, and secure multi-party computing. However, many of these areas are still in the research and development phase.

On the other hand, the trade-off between transmission distance and data rate, high hardware costs, system complexity, and side-channel vulnerabilities arising from device imperfections hinder the widespread adoption of QKD. Furthermore, the realization of large-scale, flexible, and multi-user quantum networks remains a significant engineering challenge. However, ongoing research in areas such as measurement-device-independent QKD (MDI-QKD), device-independent QKD (DI-QKD), twin-field QKD, satellite-based systems, and integrated photonic technologies provides promising advances toward mitigating these limitations. Another important approach considered alongside quantum cryptography is post-quantum cryptography (PQC). PQC provides software-based solutions that operate on existing network infrastructures and are based on mathematical problems believed to be resistant to attacks from quantum computers. The vulnerability of current public-key cryptosystems, such as the Rivest–Shamir–Adleman (RSA) and elliptic curve cryptography (ECC), to quantum attacks has significantly increased the importance of PQC. While PQC algorithms offer advantages in terms of compatibility with classical systems and scalability, their security relies on computational assumptions. In contrast, QKD stands out as a more robust solution, particularly for critical applications requiring long-term and high-level security, as it provides security based directly on the laws of physics.