Quantum cryptography uses the behavior of particles at the quantum level to secure communication in ways classical methods cannot match. Its best-known form, Quantum Key Distribution (QKD), lets two parties build a shared key such that any attempt to eavesdrop disturbs the quantum states involved and becomes detectable, so the parties learn their key was observed.
For most security professionals the more pressing issue is post-quantum cryptography, meaning classical algorithms designed to withstand attack by future quantum computers. A sufficiently capable quantum machine could break much of today’s public-key encryption, which is why NIST finalized its first post-quantum standards in 2024. The practical advice is to start inventorying where you rely on vulnerable algorithms now, because migration across an enterprise takes years, and data stolen today could be decrypted later once the hardware matures.
How is quantum cryptography tested on the CISSP?
Quantum and post-quantum topics are emerging areas within Domain 3: Security Architecture and Engineering. Candidates should grasp the threat quantum computing poses to current public-key cryptosystems, the idea behind QKD, and the migration planning organizations need to begin well before the hardware arrives.
Related terms: Cryptography, Encryption