Quantum-Safe

Cryptographic systems that remain secure against attacks from quantum computers.

Quantum-safe (or quantum-resistant) describes cryptographic algorithms and systems that are secure against adversaries with access to quantum computers. It’s often used interchangeably with post-quantum cryptography.

What’s At Risk

Shor’s algorithm threatens:

Grover’s algorithm weakens:

What’s Already Quantum-Safe

Symmetric Cryptography

With doubled key sizes:

• AES-256: Quantum-safe (128-bit security)
• SHA-384/SHA-512: Quantum-safe for hashing

Hash-Based Signatures

• SPHINCS+, XMSS, LMS
• Security from hash functions only

Achieving Quantum Safety

1. Post-Quantum Algorithms

Use PQC standards:

• ML-KEM (Kyber) for key encapsulation
• ML-DSA (Dilithium) for signatures

2. Quantum Key Distribution

Use QKD for key exchange:

• Physics-based security
• Requires specialized hardware

3. Hybrid Approaches

Combine classical and post-quantum:

• Secure if either algorithm holds
• Transition strategy

Migration Checklist

□ Inventory cryptographic assets
□ Identify quantum-vulnerable algorithms
□ Prioritize high-value, long-lifetime data
□ Plan hybrid deployment
□ Test post-quantum alternatives
□ Update protocols and standards
□ Deploy and monitor

Certification and Standards

Common Misconceptions

“AES is broken by quantum computers” No. AES with sufficient key length remains secure.

“We need to switch immediately” Urgency depends on data lifetime. “Harvest now, decrypt later” threatens long-term secrets.

“QKD solves everything” QKD only does key exchange. You still need quantum-safe algorithms for signatures, authentication, etc.

See also: Post-Quantum Cryptography, Shor’s Algorithm, Quantum Key Distribution, Lattice-Based Cryptography