OE-4.5 Quantum Cryptography
You can contrast public and private key cryptography, explain quantum key distribution and why eavesdropping is detectable, and describe experimental implementations.
Quantum key distribution is the field's one genuinely deployed product, and its security argument is physical rather than computational - measuring a quantum state disturbs it, so an eavesdropper leaves evidence. Keep it distinct from post-quantum cryptography, which is classical mathematics chosen to resist quantum attack; the two get conflated constantly. Note also that QKD distributes keys, it does not encrypt messages.
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Public and private key cryptography
Where cryptography stands today, and what the previous topic threatens. The distinction between the two kinds of key is what the threat applies to unevenly.
NPTEL: Quantum Algorithms and Cryptography · CourseQuantum key distribution
Agreeing a secret over an open channel using physics rather than mathematics. The security argument is different in kind from anything in classical cryptography.
Quantum cryptography and its security argument
Why eavesdropping is detectable here: measuring disturbs the state. That is the whole argument, and it is worth being able to state it in one sentence.
NPTEL: Quantum Algorithms and Cryptography · CourseExperimental implementation of quantum cryptography protocols
What has actually been built and over what distances. It is the item that separates the theory above from what is deployable today.
NPTEL: Quantum Algorithms and Cryptography · Course
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