up::[[Quantum Cryptography]] # Quantum Key Distribution (QKD) Quantum Key Distribution (QKD) is a method of secure communication that uses [[quantum mechanics]] principles to generate and distribute cryptographic keys securely between parties. This technique ensures that any attempt at eavesdropping between the sender and receiver can be detected, as the act of measuring a quantum system inevitably alters its state. ## Key Features - **[[Quantum Mechanics]]:** Utilizes properties of [[quantum mechanics]], specifically the behavior of photons, to detect any interception or eavesdropping. - **Tamper Detection:** Any attempt to intercept the key changes the quantum state of the system, revealing the presence of an eavesdropper. - **Forward Secrecy:** Ensures that the key distribution is secure against future advances in computing power, including [[quantum computing]]. ## How It Works QKD involves two main protocols: BB84, developed by Charles Bennett and Gilles Brassard in 1984, and E91, developed by Artur Ekert in 1991: - **BB84 Protocol:** Involves the transmission of photons in one of four polarizations, chosen at random. The receiver randomly chooses the type of polarization filter to measure the incoming photons. After the transmission, the sender and receiver compare their filter choices over an open channel (without revealing the outcomes of their measurements) to determine which photons were correctly measured. This subset forms the cryptographic key. - **E91 Protocol:** Based on [[quantum entanglement]], where a pair of entangled photons is sent to two parties. The measurements on these photons are correlated in a way that any eavesdropping attempt disrupts the correlation, alerting the parties to the presence of an interceptor. ## Problem Addressed QKD addresses the problem of secure key exchange over potentially insecure channels, providing a solution that does not rely on the assumed hardness of mathematical problems, unlike traditional cryptographic methods that could be vulnerable to [[quantum computing]]. ## Implications The use of QKD in communications promises a higher level of security in cryptographic practices, especially crucial in the age of advancing [[quantum computing]] which threatens traditional [[encryption]] methods. ## Impact QKD technology has the potential to revolutionize secure communications by providing a means to distribute keys with a security level guaranteed by the laws of quantum physics, making it virtually impossible for attackers to intercept or decipher the keys without detection. ## Defense Mechanisms - **[[Quantum Cryptography]]:** Employs principles of [[quantum mechanics]] to secure data transmission, ensuring that any eavesdropping can be detected immediately. - **Integrated Classical and Quantum Networks:** Combining QKD with traditional [[encryption]] methods to enhance overall security. ## Exploitable Mechanisms/Weaknesses While QKD itself is secure, the equipment and external communications can still have vulnerabilities, such as side-channel attacks, where an attacker gains information from the physical implementation of the cryptographic system. ## Common Tools/Software - **ID Quantique:** Offers quantum key distribution systems and related services. - **QuintessenceLabs:** Provides solutions that integrate QKD with conventional security architectures. ## Related Cybersecurity Policies - **ETSI (European Telecommunications Standards Institute) ISG QKD:** Working on standardizing QKD technologies and methodologies. - **NIST Post-Quantum Cryptography Standardization Project:** While focusing on developing quantum-resistant [[cryptographic algorithms]], it recognizes the role of QKD in future cryptographic infrastructures. ## Best Practices - Employ QKD in conjunction with existing cryptographic methods for layered security. - Regularly update and maintain quantum communication equipment to protect against physical vulnerabilities. - Educate and train relevant personnel on the principles and operational aspects of quantum communications to ensure proper implementation and use. ## Current Status As [[quantum computing]] continues to develop, the role of QKD in secure communications grows increasingly significant. Research and development are ongoing to make QKD more accessible and integrated into existing telecommunications infrastructure. ## Revision History - **2024-04-14:** Entry created.