Quantum Computing and the Future of Cryptography: How to Prepare for the Post-Quantum Era

Imagine a future where quantum computing is no longer science fiction, but a reality capable of transforming—and threatening—everything we know about digital security. This article reveals how quantum computing is about to revolutionize cryptography, the risks it brings to data protection, and, most importantly, how your organization can get ahead in the post-quantum era.

What is Quantum Computing and Why Does It Change Everything in Security?

Quantum computing represents a paradigm shift: it uses principles like superposition and entanglement to perform calculations that would be impossible for classical computers. While traditional computers work with bits (0 or 1), qubits can exist in multiple states at once, allowing quantum computers to solve complex problems at exponential speeds.

According to Tempest, companies like IBM, Google, and D-Wave have already surpassed the 1,000-qubit mark by 2025, although they still face challenges in stability and practical application. Progress is fast—and inevitable.

The Quantum Threat to Current Cryptography

Algorithms Vulnerable to Quantum Computing

The greatest fear is that quantum computers will break the cryptographic systems that protect everything today—from banks to governments.

Shor’s Algorithm and the Fall of Asymmetric Cryptography

In 1994, Peter Shor created a quantum algorithm capable of factoring large integers quickly—something impossible for classical computers. This directly threatens:

• RSA: the backbone of internet security;
• ECC: used in mobile and blockchain;
• Diffie-Hellman: for key exchange;

Tempest warns: “a sufficiently powerful quantum computer could break a 2048-bit RSA key in hours or days, while a classical supercomputer would take billions of years.”

Grover’s Algorithm and the Reduced Strength of Symmetric Cryptography

Grover’s algorithm accelerates brute-force attacks, effectively halving the security of symmetric algorithms like AES. For example:

• AES-128 would have an effective security of 64 bits;
• AES-256 would drop to 128 bits.

While the impact is less dramatic than on asymmetric systems, it’s still a significant reduction.

Threat Timeline

When will the threat become real? Experts differ, but the consensus is:

• 2025-2030: first algorithms broken in the lab;
• 2030-2035: practical risk for production systems;
• 2035+: widespread threat to traditional cryptography.

Tempest highlights the concept of “harvest now, decrypt later”: adversaries are already collecting encrypted data today to decrypt it when the technology matures.

Post-Quantum Cryptography: The New Security Frontier

What is Post-Quantum Cryptography?

Post-quantum cryptography (PQC) refers to classical algorithms designed to withstand attacks from both quantum and traditional computers. The goal, according to Tempest, is to create solutions based on mathematical problems that remain hard even for quantum computing.

Main Approaches in Post-Quantum Cryptography

The NIST leads the standardization of PQC algorithms. The main families are:

• Lattice-based: CRYSTALS-Kyber and Dilithium (efficient, small keys);
• Code-based: Classic McEliece, BIKE (proven resistance);
• Multivariate: Rainbow, GeMSS (fast signatures, large keys);
• Hash-based: SPHINCS+, LMS/HSS (security based on hash functions);
• Isogeny-based: SIKE (compact keys, but now vulnerable).

By 2025, CRYSTALS-Kyber, Dilithium, FALCON, and SPHINCS+ are already NIST standards and are being adopted globally.

How to Prepare for the Post-Quantum Transition

Assess Risks and Build a Crypto Inventory

1. Map all systems using cryptography;
2. Document algorithms, key sizes, and use cases;
3. Prioritize critical systems and long-lived data;
4. Assess the impact of potential compromise;
5. Compare system lifespans with the evolution of the quantum threat.

Migration Strategies

• Hybrid approach: use classical and post-quantum algorithms together (e.g., RSA + Kyber);
• Crypto agility: design systems to easily swap algorithms;
• Risk-based prioritization: start with the most critical and long-lived systems.

Practical Challenges

• Performance: some PQC algorithms require more processing and bandwidth;
• Integration: many legacy systems don’t support new algorithms;
• Interoperability: you’ll need to operate in mixed environments during the transition.

Practical Examples and Use Cases

• PKI: implement hybrid certificates and reduce the validity of traditional certificates;
• TLS/HTTPS: adopt extensions for post-quantum algorithm negotiation and hybrid groups;
• Blockchain: create key migration mechanisms and educate the community about risks.

Trends and What’s Next

• Quantum cryptography (QKD): security based on physical laws, but with practical limitations;
• PQC and QKD are complementary: PQC for broad systems, QKD for high-security links;
• Accelerated research: new algorithms, optimizations, and hardware implementations emerge every year;
• Regulation: NIST, NSA, ENISA, and ANPD are already publishing guidelines for the post-quantum era.

Practical Recommendations

Immediate actions (2025-2026):

• Educate teams and leadership about the quantum threat;
• Inventory all uses of cryptography;
• Define responsibilities and create a migration roadmap;
• Monitor standards and join industry groups.

Medium term (2026-2028):

• Test PQC algorithms in pilot environments;
• Update critical infrastructure (PKI, VPNs, identity);
• Train teams and review internal policies.

Long term (2028+):

• Migrate critical systems to PQC;
• Audit implementations and validate compliance;
• Prepare incident response plans for quantum-related breaches;
• Innovate and contribute to research.

Conclusion

Quantum computing is both a promise and a challenge for digital security. While the threat is still developing, sensitive data is already at risk due to “harvest now, decrypt later.” The good news is that the community is preparing: post-quantum algorithms are being standardized and implemented.

As Tempest highlights, the transition to post-quantum cryptography is a strategic imperative. Organizations that act now will be ahead, turning the challenge into an opportunity to strengthen their security.

FAQ – Frequently Asked Questions

1. When will quantum computers be a practical threat?
Experts estimate 5 to 15 years (2030-2040) for computers capable of breaking RSA-2048. But the threat already exists for data that needs long-term confidentiality.

2. Are AES and symmetric cryptography also threatened?
Yes, but to a lesser extent. Grover’s algorithm halves the security. AES-256 is still considered safe for the post-quantum era.

3. How does the transition affect IoT and embedded devices?
Resource-constrained devices will face challenges. Solutions include optimizations, using gateways, and in some cases, hardware replacement.

4. Are current VPNs vulnerable to quantum attacks?
Yes. Most VPNs use vulnerable algorithms. Prioritize upgrading to hybrid or post-quantum options.

5. How can organizations stay updated on quantum computing and PQC?
Follow NIST publications, join groups like QED-C and Cloud Security Alliance, stay in touch with vendors, and seek specialized consulting.

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References:

1. Tempest. (2025). “Computação Quântica e Criptografia Pós-Quântica”. Available at: https://www.tempest.com.br/blog/computacao-quantica-e-criptografia-pos-quantica/
2. NIST. (2025). “Post-Quantum Cryptography Standardization”. Available at: https://csrc.nist.gov/Projects/post-quantum-cryptography/post-quantum-cryptography-standardization
3. Tempest. (2024). “Criptografia Pós-Quântica: O que é e por que você deveria se importar”. Available at: https://www.tempest.com.br/blog/criptografia-pos-quantica/
4. IBM. (2025). “Quantum Computing and Post-Quantum Cryptography”. Available at: https://www.ibm.com/quantum/quantum-computing-and-post-quantum-cryptography
5. NSA. (2024). “Commercial National Security Algorithm Suite 2.0”. Available at: https://media.defense.gov/2022/Sep/07/2003071834/-1/-1/0/CSA_CNSA_2.0_ALGORITHMS_.PDF
6. ENISA. (2025). “Post-Quantum Cryptography: Current state and quantum mitigation”. Available at: https://www.enisa.europa.eu/publications/post-quantum-cryptography-current-state-and-quantum-mitigation