Quantum mechanics applied to secrecy.
WHAT QUANTUM KEY DISTRIBUTION IS
Using quantum properties to establish a shared secret, where interception is detectable.
WHY INTERCEPTION IS DETECTABLE
Measuring a quantum state disturbs it, which the parties can observe.
WHAT IT PROVIDES
Key exchange whose security rests on physics rather than computational difficulty.
WHAT IT REQUIRES
Specialised hardware A direct optical path, or trusted relay nodes Distance limits
WHAT THAT MEANS PRACTICALLY
It is used in specific high-value links, not across the internet.
WHAT IT DOES NOT SOLVE
Authentication, which still requires classical means Everything above the key exchange layer
WHAT QUANTUM RANDOM NUMBER GENERATION PROVIDES
Randomness derived from quantum processes rather than algorithms.
WHY THAT CAN MATTER
Weak randomness has broken real cryptographic systems.
WHAT TO DISTINGUISH CAREFULLY
Quantum cryptography: using quantum effects
Post-quantum cryptography: classical algorithms resistant to quantum attack
WHY THAT DISTINCTION MATTERS
They are frequently confused, and only the second is relevant to most organisations.
