What is Quantum Computing Threat?
The risk that sufficiently powerful quantum computers will break widely-used encryption algorithms, potentially exposing all currently encrypted data.
Quantum computers don't just break encryption faster — they use entirely different mathematical approaches that make certain cryptographic problems trivial.
What Breaks
- RSA: Factoring large numbers becomes easy (Shor's algorithm)
- Elliptic Curve Cryptography: Discrete logarithm problem becomes easy
- Diffie-Hellman key exchange: Same mathematical weakness
- DSA/ECDSA: Digital signatures broken
What Survives
- AES-256: Grover's algorithm reduces effective security to AES-128 (still strong)
- SHA-256: Still resistant with doubled output
- Post-quantum algorithms: Lattice-based, hash-based, code-based cryptography
Timeline
- Current quantum computers: ~1,000 qubits (not enough)
- Breaking RSA-2048 requires: ~4,000+ logical qubits
- Estimated timeline: 10-20 years (opinions vary widely)
"Harvest Now, Decrypt Later"
Intelligence agencies are likely storing encrypted communications today, planning to decrypt them when quantum computers arrive. If your secrets need to be protected for decades, post-quantum encryption is already necessary.
Action Items
- Use services implementing post-quantum key exchange (Signal already does)
- Migrate to post-quantum TLS as it becomes available
- Use AES-256 for symmetric encryption (quantum-resistant)
- Plan for cryptographic agility — the ability to switch algorithms quickly
Related Terms
Elliptic Curve Cryptography
A public-key cryptography approach based on the algebraic structure of elliptic curves. ECC provides equivalent security to RSA with much smaller key sizes, making it ideal for mobile devices, IoT, and performance-critical applications.
Post-Quantum Cryptography
Cryptographic algorithms designed to resist attacks from both classical and quantum computers — the next generation of encryption being standardized to replace RSA, ECC, and other vulnerable algorithms.
RSA
One of the first public-key cryptosystems, RSA is based on the mathematical difficulty of factoring large prime numbers. Named after its inventors Rivest, Shamir, and Adleman, it's still widely used for key exchange and digital signatures.
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