Post-Quantum Encryption: What the Future Holds for File Security

The encryption protecting the internet today — RSA, Elliptic Curve Cryptography (ECC), and Diffie-Hellman key exchange — is mathematically secure against classical computers. Quantum computers will change that. The question isn't whether, but when. The US NIST has already standardised the first post-quantum algorithms. Here's what this means for file security.

Why Quantum Computers Threaten Current Encryption

Classical computers factor large numbers in exponential time — too slow to break RSA in any practical sense. Quantum computers running Shor's algorithm can factor large numbers in polynomial time. An RSA-2048 key that would take classical computers billions of years to crack could theoretically be broken by a sufficiently powerful quantum computer in hours.

AES-256, notably, is believed to be quantum-resistant. Symmetric encryption requires a more modest doubling of key length to maintain security against quantum attacks (Grover's algorithm). AES-128 becomes effectively AES-64 against quantum; AES-256 remains adequately secure.

NIST's Post-Quantum Standards (2024)

After an eight-year competition, NIST standardised the first post-quantum algorithms:

• CRYSTALS-Kyber (ML-KEM) — key encapsulation mechanism, replacing RSA and ECDH
• CRYSTALS-Dilithium (ML-DSA) — digital signatures, replacing ECDSA
• SPHINCS+ (SLH-DSA) — hash-based signatures as a conservative backup

"Harvest Now, Decrypt Later"

Nation-state actors are already collecting encrypted network traffic today, expecting to decrypt it when quantum computers mature. If your sensitive files were shared in 2024 and are still classified as secret, they may be decrypted in 2035. For long-lived secrets, transitioning to post-quantum cryptography now is prudent.

What to Do Today

For most people and businesses, today's encryption (TLS 1.3, AES-256) is adequate for files that will lose sensitivity within a few years. For long-lived secrets — cryptographic keys, trade secrets, national security materials — begin planning migration to NIST-approved post-quantum algorithms.