Why Today's Encryption Has an Expiration Date
The cryptographic algorithms that protect virtually all digital communication today. RSA, ECDSA, ECDH, Diffie-Hellman. are built on mathematical problems that classical computers cannot efficiently solve. Quantum computers will solve them.
This isn't a theoretical concern for a distant future. It's an active threat that organizations must begin addressing now.
What Breaks and Why
RSA: Integer Factorization
RSA security depends on the difficulty of factoring the product of two large prime numbers. The best classical algorithm (General Number Field Sieve) requires sub-exponential time. Shor's algorithm reduces this to polynomial time on a quantum computer.
| RSA Key Size | Classical Attack Time | Quantum Attack Time (Shor's) |
|---|---|---|
| RSA-2048 | ~1030 years | Hours to days |
| RSA-3072 | ~1040 years | Hours to days |
| RSA-4096 | ~1050 years | Hours to days |
Simply increasing key sizes does not help against quantum attacks. Shor's algorithm scales polynomially, meaning any classical key size is vulnerable.
ECC: Elliptic Curve Discrete Logarithm
Elliptic Curve Cryptography (ECC) offers the same security as RSA with much smaller keys, making it the preferred choice for mobile, IoT, and performance-sensitive applications. However, it's equally vulnerable: Shor's algorithm solves the elliptic curve discrete logarithm problem efficiently.
Symmetric Algorithms: Grover's Speedup
AES, SHA-2, and other symmetric algorithms face a quadratic speedup from Grover's algorithm. cutting effective security levels in half. However, this is manageable by doubling key lengths (e.g., AES-128 → AES-256).
Harvest Now, Decrypt Later (HNDL)
The Most Urgent Threat
Adversaries. particularly nation-state actors. are already collecting encrypted data today with the intention of decrypting it once quantum computers become powerful enough. This is known as "Harvest Now, Decrypt Later" (HNDL) or "Store Now, Decrypt Later" (SNDL).
This means the quantum threat is not a future problem. it's a present one for any data that must remain confidential for more than 10 years:
- Government classified data. National security secrets with 25-50+ year shelf life
- Healthcare records. Patient data protected for decades under HIPAA
- Financial data. Trade secrets, M&A data, long-term contracts
- Personal data. Biometric data, genetic information. once compromised, cannot be changed
- Critical infrastructure. SCADA/ICS systems with 20-30 year operational lifespans
When Will Quantum Computers Break Encryption?
No one knows exactly, but estimates converge on a range:
| Source | Estimate for Cryptographically Relevant QC |
|---|---|
| Global Risk Institute (2024) | 50% chance by 2033-2037 |
| NIST | Planning for 2030s as prudent target |
| BSI (Germany) | "Can no longer be ruled out within 10-15 years" |
| Government mandates | Most require migration completion by 2030-2035 |
The Migration Timeline Problem
Migrating an organization's cryptographic infrastructure is a multi-year effort. It involves:
- Discovering all cryptographic usage (often undocumented)
- Assessing risk and prioritizing systems
- Testing PQC algorithms for compatibility and performance
- Updating standards, policies, and compliance frameworks
- Deploying across production infrastructure
- Coordinating with vendors and supply chain partners
Industry estimates suggest 5-15 years for large organizations to complete full migration. If quantum computers arrive by 2035, organizations that haven't started by 2025 are already behind.
Key Takeaways
Review the main concepts from this chapter before moving to the next one.