10.2 Quantum Key Distribution Protocols

Quantum Key Distribution (QKD) uses quantum mechanics to securely exchange cryptographic keys. It's a game-changer in secure communication, detecting eavesdropping attempts and creating unbreakable keys using quantum states of particles like photons.

Various QKD protocols exist, each with unique features. BB84 uses single photons, E91 relies on entanglement, and B92 simplifies the process. All share core security features like eavesdropping detection and immunity to future computational advances.

Quantum Key Distribution Fundamentals

Purpose of quantum key distribution

Top images from around the web for Purpose of quantum key distribution

• 

  High-Speed Quantum Key Distribution and Beyond View original

  Is this image relevant?

• 

  High-Speed Quantum Key Distribution and Beyond View original

  Is this image relevant?

1 of 1

Top images from around the web for Purpose of quantum key distribution

• 

  High-Speed Quantum Key Distribution and Beyond View original

  Is this image relevant?

• 

  High-Speed Quantum Key Distribution and Beyond View original

  Is this image relevant?

1 of 1

• Quantum Key Distribution (QKD) securely exchanges cryptographic keys using quantum mechanics principles
• QKD establishes secure communication between two parties and detects eavesdropping attempts
• Key features utilize quantum states of particles (photons) and rely on no-cloning theorem for information-theoretic security
• Applications include secure communication channels, financial transactions, and government/military communications

Concept of quantum key exchange

• Quantum key exchange process involves sender encoding information in quantum states, receiver measuring states, and post-processing to derive shared key
• Creates random, secure key known only to communicating parties
• Utilizes quantum properties of superposition, entanglement, and quantum measurement
• Key steps include quantum state preparation, transmission, measurement, sifting, error correction, and privacy amplification

Quantum Key Distribution Protocols

Comparison of QKD protocols

• BB84 protocol developed by Bennett and Brassard (1984) uses single photons in different polarization states with four possible quantum states and two non-orthogonal bases
• E91 protocol proposed by Artur Ekert (1991) utilizes entangled photon pairs based on Bell's theorem allowing device-independent QKD
• B92 protocol simplifies BB84 using only two non-orthogonal quantum states requiring fewer resources
• Protocols differ in number of quantum states used, reliance on entanglement, efficiency in key generation, and practical implementation challenges

Security features in QKD protocols

• Security features include eavesdropping detection, forward secrecy, and immunity to future computational advances
• Common assumptions involve perfect single-photon sources, ideal detectors, and lossless quantum channels
• Security proofs based on information theory and quantum mechanics provide unconditional security in ideal conditions
• Practical security considerations address photon number splitting attacks, side-channel attacks, and equipment imperfections
• Protocol-specific features include random basis selection (BB84), Bell's inequality violation (E91), and non-orthogonal state discrimination (B92)
• Quantum bit error rate (QBER) indicates potential eavesdropping and sets threshold for secure key generation
• Authentication requirements prevent man-in-the-middle attacks
• Privacy amplification techniques reduce potential information leakage to eavesdroppers