Security Aspects of Practical Quantum Cryptography

  • Gilles Brassard
  • Norbert Lütkenhaus
  • Tal Mor
  • Barry C. Sanders
Conference paper
Part of the Lecture Notes in Computer Science book series (LNCS, volume 1807)


The use of quantum bits (qubits) in cryptography holds the promise of secure cryptographic quantum key distribution schemes. Unfortunately, the implemented schemes are often operated in a regime which excludes unconditional security. We provide a thorough investigation of security issues for practical quantum key distribution, taking into account channel losses, a realistic detection process, and modifications of the “qubits” sent from the sender to the receiver. We first show that even quantum key distribution with perfect qubits might not be achievable over long distances when fixed channel losses and fixed dark count errors are taken into account. Then we show that existing experimental schemes (based on weak pulses) currently do not offer unconditional security for the reported distances and signal strength. Finally we show that parametric downconversion offers enhanced performance compared to its weak coherent pulse counterpart.


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Copyright information

© Springer-Verlag Berlin Heidelberg 2000

Authors and Affiliations

  • Gilles Brassard
    • 1
  • Norbert Lütkenhaus
    • 2
  • Tal Mor
    • 3
    • 4
  • Barry C. Sanders
    • 5
  1. 1.Département IROUniversité de MontréalMontréalCanada
  2. 2.Helsinki Institute of PhysicsHelsingin yliopistoFinland
  3. 3.Electrical EngineeringCollege of Judea and SamariaArielIsrael
  4. 4.Electrical EngineeringUniversity of California at Los AngelesLos AngelesUSA
  5. 5.Department of PhysicsMacquarie UniversitySydney New South WalesAustralia

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