Quantum Cryptography
Home /
Glossary Index /
Alphabet Q
RSA and elliptic curve cryptography have protected internet communications for decades. Quantum computers will break them. Not maybe. Not someday. Within the next decade, a cryptographically relevant quantum computer could decrypt today’s encrypted communications, forge digital signatures, and undermine trusted systems. The risk is real and immediate because of harvest now, decrypt later. Attackers collect encrypted data today. They wait for quantum computers to decrypt it tomorrow. Your data could be exposed years from now even if you never lose control of it.
What Is Quantum Cryptography?
Quantum cryptography is a collection of techniques that apply the principles of quantum mechanics to guarantee the security of communications. Unlike classical cryptography based on mathematical assumptions, quantum cryptography uses physics. Eavesdropping is detectable. Two primary defense approaches are emerging. Post-quantum cryptography (PQC) uses mathematical algorithms believed resistant to quantum attacks and runs on existing classical infrastructure. Quantum key distribution (QKD) provides physics-based security by using quantum effects to detect eavesdropping on key exchange.
The Threat
Modern cryptography relies on mathematical problems that classical computers cannot solve efficiently. Factoring large numbers and computing discrete logarithms are hard problems. Quantum computers solve these problems efficiently using Shor’s algorithm. When a sufficiently powerful quantum computer exists, it will break RSA and elliptic curve cryptography instantly. No quantum computer can break these systems yet. But the risk of harvest now, decrypt later is real. Data encrypted and stored or transmitted today could be decrypted in the future once sufficiently powerful quantum computers become available.
Post-Quantum Cryptography (PQC)
PQC uses mathematical algorithms believed resistant to quantum attacks. These algorithms run on existing classical infrastructure. Organizations can implement PQC largely with software updates. No special hardware required. The U.S. National Institute of Standards and Technology (NIST) released the first post-quantum standards in summer 2024. Binding procedures now exist to serve as a new international basis for secure communication. Major technology providers including Google, Microsoft, and Amazon have begun aligning their security protocols with these new standards. Everyday applications such as web browsers and messaging services are now testing quantum-hardened connections.
Quantum Key Distribution (QKD)
QKD uses quantum mechanics to securely exchange encryption keys between parties. The security of QKD is based on the laws of physics, not mathematical assumptions. Any eavesdropping attempt changes the quantum state and becomes detectable. QKD requires special hardware such as photon sources or detectors and often functions via fiber optic or satellite connections. It offers a level of security based on fundamental physics. Eavesdropping simply becomes detectable.
The Future Will Be Hybrid
The future likely lies in a combination of both approaches. Hybrid systems will combine PQC algorithms with quantum-safe key exchange, creating a multi-layered security model. No single approach solves every use case. PQC works for all applications but is not yet fully standardized. QKD provides physics-based security but requires hardware.
What Your Organization Should Do Now
Start your migration to quantum-safe cryptography. The countdown has begun. Organizations that integrate the new standards early will secure their own communications and technological sovereignty. Take these actions today. Inventory all cryptographic systems. Identify where you use RSA and elliptic curve. Prioritize sensitive data with long retention requirements for migration. Monitor NIST post-quantum standards development. Begin testing PQC algorithms in non-critical environments. Require quantum-safe capabilities from vendors. Plan for hybrid deployments combining PQC with existing cryptography during transition.
Quantum-resistant cryptography is not optional. Regulators will eventually mandate it. Early adopters gain security and competitive advantage. Late adopters face urgent migrations under pressure. Do not wait. The threat is coming.
