Quantum Key Distribution and Qubits ECES Practice Questions (Page 8)

Questions 36–40

1. 36application · medium

   A hospital network needs to securely share patient data between two campuses. They are considering QKD to distribute encryption keys. What is a key advantage of QKD over classical key exchange for this scenario?

   • AQKD is faster than classical key exchange.
   • BQKD provides detection of any eavesdropping attempt, ensuring the key is secure.
   • CQKD can be used over any distance without limitations.
   • DQKD does not require any additional hardware beyond existing network equipment.
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2. 37application · medium

   A network administrator is evaluating QKD for a high-security link. They ask how QKD can detect an eavesdropper who passively intercepts and measures photons without altering them. What is the correct response?

   • AQKD uses classical encryption to detect any interception of the quantum channel
   • BQKD detects the eavesdropper by comparing a subset of the sifted key bits over the public channel
   • CQKD detects eavesdropping by monitoring the intensity of the laser pulses for any drop in signal
   • DQKD cannot detect passive eavesdropping because the eavesdropper does not disturb the photons
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4. 38foundation · easy

   How does QKD detect the presence of an eavesdropper?

   • ABy using a trusted third party to monitor the quantum channel.
   • BBy comparing a portion of the sifted key and checking for an unusually high error rate.
   • CBy measuring the speed of photons to detect any delay caused by interception.
   • DBy encrypting the key with a classical algorithm and checking for decryption failures.
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5. 39application · medium

   A telecom company is planning to deploy QKD between two cities that are 400 km apart. They have a choice of using optical fiber or free-space optical links. What is the most significant limitation they will face with fiber-based QKD?

   • APhoton loss in the fiber limits the distance to a few hundred kilometers without trusted repeaters
   • BFiber-based QKD is limited by the speed of light, making key exchange slower than classical methods
   • CFiber-based QKD cannot operate at night due to background light interference
   • DFiber-based QKD requires a clear line of sight between the two locations
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6. 40application · medium

   A company is considering QKD for securing their communication. They are concerned about the cost and complexity. Which statement best describes a limitation of QKD that they should consider?

   • AQKD is only useful for short distances and cannot be used in metropolitan networks.
   • BQKD is only secure against passive eavesdropping, not active attacks.
   • CQKD cannot be integrated with existing classical encryption systems.
   • DQKD requires a dedicated quantum channel, which can be expensive to deploy and maintain.
   Reveal Solution Discussion Select an answer first