Quantum computing vs. encryption: Why post-quantum algorithms are essential

From online banking to cloud authentication – cryptography, the science of secure data encryption and authentication, forms the foundation of data security. However, current encryption methods may soon become obsolete.

The reason? Quantum computers.

Still in development, quantum computers could, in the near future, break many widely used encryption algorithms within minutes. The solution lies in post-quantum algorithms—new, resilient encryption methods that even powerful quantum computers cannot compromise.
Since integrating new encryption standards takes years, now is the right time to prepare.

Why Is Post-Quantum Cryptography Necessary?

Classical cryptography relies on mathematical problems such as the factorization of large numbers (RSA) and discrete logarithms (ECC). These methods are vulnerable to Shor’s algorithm, the most significant threat to traditional asymmetric encryption like RSA, ECC, and DH. This algorithm enables the exponentially faster factorization of large numbers and solving discrete logarithm problems, rendering these methods ineffective.

While classical computers would take thousands of years to break RSA-2048—a widely used standard for secure communication, digital signatures, and certificates—a sufficiently powerful quantum computer could accomplish this in just a few hours.

A particularly alarming aspect is that many encrypted datasets today—such as medical records, blockchain transactions, and corporate secrets—have a long lifespan. Attackers could already be intercepting and storing data today, planning to decrypt it later when quantum technology matures (“Harvest Now, Decrypt Later”). This makes it essential to transition to quantum-safe encryption as soon as possible.

The Path to Post-Quantum Cryptography

International organizations have been working for years to develop standardized quantum-resistant algorithms. The U.S. National Institute of Standards and Technology (NIST) and the EU Commission are leading these efforts. The following mathematical approaches are at the forefront:

1) Lattice-Based Cryptography

• Based on the difficulty of finding the shortest vector in high-dimensional lattices—even for quantum computers, this remains nearly impossible.
• Key algorithms: Kyber (encryption) and Dilithium (digital signatures).

2) Hash-Based Signatures

• Uses cryptographic hash functions instead of classical public-key cryptography.
• Example: SPHINCS+, a quantum-secure signature scheme with structural similarities to blockchain technologies.

3) Multivariate Quadratic Equations

• Relies on the difficulty of solving nonlinear equation systems. However, it is less efficient than lattice-based solutions in terms of key length and computational effort.
• Example: Rainbow (digital signatures).

4) Code-Based and Isogeny-Based Cryptography

• Code-Based Cryptography utilizes error-correcting codes.
  • Example: Classic McEliece, known for its high security but large key sizes.
• Isogeny-Based Cryptography relies on complex mathematical transformations of elliptic curves.
  • Example: SIDH (Supersingular Isogeny Diffie-Hellman)—however, a vulnerability discovered in 2022 compromised its security.

Standardized Algorithms for the Future

In 2024, NIST recommended the following algorithms for standardization:

• CRYSTALS-Kyber (FIPS 203): Encryption for secure websites and general applications.
• CRYSTALS-Dilithium (FIPS 204): Digital signature protection.
• SPHINCS+ (FIPS 205): Hash-based digital signatures.
• FALCON (FIPS draft): Another option for digital signatures.

These algorithms represent the first generation of quantum-safe encryption methods. Further developments are underway to address specific application fields.

A noteworthy innovation is the ASCON algorithm family, developed at TU Graz. Designed for resource-constrained environments (e.g., IoT and OT devices), ASCON has been officially recognized by NIST as an international standard for lightweight encryption.

Challenges and Practical Implementation

Despite the advancements in quantum computing, several technical hurdles remain:

• Scalability and Error Correction: Even leading companies like Google struggle with the stability and error rates of quantum chips.
• Migration Effort: Post-quantum algorithms often require significantly more computational power and storage.
• Hybrid Transition Solutions: To gradually secure existing systems, hybrid encryption—combining classical and quantum-safe methods—is a practical approach.

The Need for Action: Preparing for the Quantum Era

Post-quantum cryptography is no longer a distant concept, it is a necessity. IT professionals and security leaders should proactively prepare for the migration to quantum-resistant algorithms by:

1. Conducting a risk assessment: Identify which systems still rely on vulnerable encryption.
2. Launching pilot projects: Test new algorithms in non-critical areas first.
3. Monitoring industry trends: Stay updated on developments from NIST, ENISA, and other standardization bodies.
4. Building partnerships: Engage with manufacturers and authorities to implement solutions early.

The quantum revolution may arrive sooner than expected. Organizations that take a proactive approach will protect their data in the long term and minimize future security risks.

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Ressources:
https://csrc.nist.gov/projects/post-quantum-cryptography
https://digital-strategy.ec.europa.eu/en/library/recommendation-coordinated-implementation-roadmap-transition-post-quantum-cryptography
https://ascon.isec.tugraz.at/