Post-Quantum Cryptography: What It Is, How It Works, and How to Prepare Your Organization.

Last Updated March 2026

Quantum-Proof Security

Post-quantum cryptography is the field of developing encryption algorithms that can resist attacks from quantum computers. It is not a theoretical concern for a distant future. NIST finalized its first post-quantum cryptographic standards in August 2024. The U.S. government has set 2035 as the target deadline for completing the migration of national security systems. Intelligence agencies have already warned that nation-state actors are harvesting encrypted data today to decrypt it once quantum computers become powerful enough to do so.

The encryption methods that currently protect most of the world’s digital communications — RSA, elliptic-curve cryptography, and Diffie-Hellman key exchange — are vulnerable to a sufficiently powerful quantum computer running Shor’s algorithm. That is not a flaw in implementation. It is a structural weakness in the mathematical problems that those algorithms rely on.

This guide explains how post-quantum cryptography works, what the finalized NIST standards mean for your organization, which industries face the most urgent exposure, and what a practical migration roadmap looks like for teams beginning the transition now.

According to IBM, a quantum computer capable of breaking RSA-2048 encryption would require approximately 4,000 logical qubits. Current quantum computers operate in the hundreds of physical qubits, but the trajectory of development is accelerating. The U.S. government has set 2035 as its target deadline for migrating national security systems to post-quantum cryptography.

The Quantum Threat to Modern Cryptography

As quantum computing advances, the cryptography that secures our digital world is under threat. The potential for quantum computers to break certain types of encryption has significant implications for data security.

How Quantum Computers Break Traditional Encryption

Quantum computers can perform complex calculations at speeds that are unattainable by classical computers. This capability allows them to factor large numbers and compute discrete logarithms, which are the foundation of many public-key cryptosystems. For instance, Shor’s algorithm can factor large numbers exponentially faster than the best-known classical algorithms, rendering RSA and elliptic-curve cryptography vulnerable.

Timeline of Quantum Computing Development

The development of quantum computing has been rapid. From the first experimental quantum computers to the current advancements, the field has seen significant milestones. Notable achievements include demonstrating quantum supremacy and developing more stable, scalable quantum computing architectures.

The “Harvest Now, Decrypt Later” Threat

Of all the risks associated with quantum computing, harvest now, decrypt later is the one that requires action today — not when quantum computers become powerful enough to break encryption directly.

The attack is straightforward in concept. An adversary can now intercept and store encrypted data, whereas it remains secure under classical encryption. They hold that data until a cryptographically relevant quantum computer becomes available — at which point they decrypt it retroactively. The data has already been stolen. The encryption that protected it during transmission is now irrelevant.

This threat is not theoretical. Intelligence agencies, nation-state actors, and sophisticated criminal organizations have both the motive and the infrastructure to execute large-scale data interception and storage operations. The open question is not whether this is happening — it almost certainly is — but rather how much data is being stored and what will be decipherable when quantum capabilities arrive.

The timeline matters enormously here. Most estimates from researchers and government agencies place the emergence of a cryptographically relevant quantum computer somewhere between 2030 and 2035, though some models suggest earlier. The U.S. National Security Agency has already mandated post-quantum migration timelines for national security systems. CISA has published urgent guidance for critical infrastructure operators. Neither agency treats this as a distant concern.

The industries most exposed to harvest now, decrypt later are those where data has long-term sensitivity: financial services, where transaction records and customer data may carry value for decades; healthcare, where patient records carry lifetime confidentiality requirements; government and defense, where classified information may remain sensitive for 25 years or more; and legal and intellectual property, where trade secrets and privileged communications have indefinite value.

For these sectors, the relevant question is not “when should we start migrating?” The answer is already: now. Any data transmitted or stored today under classical encryption that must remain confidential beyond approximately 2030 is at risk.

What is Post-Quantum Cryptography?

Post-quantum cryptography is an emerging field that focuses on developing cryptographic techniques to secure data against attacks by quantum computers. As quantum computing advances, it poses a significant threat to traditional encryption methods, making the need for quantum-resistant cryptography increasingly important.

Core Principles and Objectives

The core principle of post-quantum cryptography is to develop algorithms that are resistant to both classical and quantum computer attacks. Its primary objective is to ensure the long-term security of data, even in the presence of powerful quantum computers.

Difference Between Quantum Cryptography and Post-Quantum Cryptography

While quantum cryptography utilizes the principles of quantum mechanics to secure data, post-quantum cryptography focuses on developing classical cryptographic algorithms that can resist attacks from quantum computers. The two are distinct, with quantum cryptography relying on the no-cloning theorem, and post-quantum cryptography developing new algorithms to withstand quantum threats.

Why Traditional Encryption Methods Are Vulnerable

Traditional encryption methods, such as RSA and elliptic curve cryptography, are vulnerable to quantum computer attacks because they rely on problems that can be solved by quantum computers, like factoring large numbers. Post-quantum cryptography aims to replace these methods with quantum-resistant alternatives.

Types of Post-Quantum Cryptographic Algorithms

Post-quantum cryptography involves developing algorithms that can withstand attacks from quantum computers. As the world moves towards a quantum-enabled future, it’s crucial to understand the different types of cryptographic algorithms being developed to ensure security in this new era.

• Lattice-Based Cryptography: Lattice-based cryptography is a promising area that relies on the hardness of problems related to lattices. It’s versatile, enabling the construction of various cryptographic primitives, including public-key encryption and digital signatures.
• Hash-Based Cryptography: Hash-based cryptography utilizes hash functions to construct cryptographic algorithms. It’s known for its simplicity and the ability to provide security proofs based on well-understood problems.
• Code-Based Cryptography: Code-based cryptography, rooted in error-correcting codes, provides an alternative approach to post-quantum security. It has been studied since McEliece’s original proposal in 1978 and remains a viable option due to its strong, well-analyzed security foundations. For further background, NIST’s official post-quantum cryptography project page provides detailed technical specifications for all evaluated algorithm families.
• Multivariate Cryptography: Multivariate cryptography is based on the difficulty of solving systems of nonlinear equations over finite fields. It presents a potentially viable path for post-quantum cryptographic solutions.
• Isogeny-Based Cryptography: Isogeny-based cryptography leverages the mathematical concept of isogenies between elliptic curves. It provides a promising avenue for constructing quantum-resistant cryptographic protocols.

These approaches to post-quantum cryptography are crucial for developing quantum-safe cryptography solutions. Understanding and implementing these algorithms will be essential to ensuring the effectiveness of cryptography in the era of quantum computing.

NIST has already selected its primary post-quantum candidates: CRYSTALS-Kyber for encryption and CRYSTALS-Dilithium for digital signatures. These are expected to become the dominant standards that organizations worldwide adopt as they transition to quantum-safe security.

NIST Standardization Process and Current Status

In August 2024, NIST finalized its first three post-quantum cryptographic standards, marking the most significant milestone in cryptographic standardization in decades. Organizations that are still treating this as a future concern need to update their timelines — the standards are final, and the migration clock has started.

The 3 finalized standards are:

1. ML-KEM (Module Lattice Key Encapsulation Mechanism), formerly known as CRYSTALS-Kyber, is the primary standard for public-key encryption and key exchange. It is based on lattice problems and is designed for general use across most encryption scenarios.
2. ML-DSA (Module Lattice Digital Signature Algorithm), formerly known as CRYSTALS-Dilithium, is the primary standard for digital signatures. It offers strong security and relatively small signature sizes, making it practical for most enterprise applications.
3. SLH-DSA (Stateless Hash-Based Digital Signature Algorithm), formerly known as SPHINCS+, is a hash-based digital signature standard that provides an alternative to ML-DSA. Its security relies on various mathematical assumptions, which provide organizations with a backup option if lattice-based approaches face future vulnerabilities.

A fourth algorithm, FN-DSA (based on FALCON), is expected to be standardized separately for applications where signature size is a critical constraint.

Beyond NIST, the U.S. Cybersecurity and Infrastructure Security Agency (CISA) has published its own post-quantum readiness guidance, urging critical infrastructure operators to begin migration planning immediately. The European Union Agency for Cybersecurity (ENISA) has issued parallel recommendations. Global standardization is not lagging behind — it is already underway.

For organizations still planning their cryptographic roadmap, the standard selection question is largely settled. The active question now is how and when to migrate, not which algorithms to adopt.

Sources: NIST Post-Quantum Cryptography project, CISA Post-Quantum Cryptography guidance

Implementing Post-Quantum Cryptography in Organizations

With the rise of quantum computers, traditional encryption methods are becoming obsolete, necessitating a shift to post-quantum cryptography. Organizations must now consider how to integrate these new cryptographic techniques into their existing infrastructure.

• Hybrid Approaches for Transition: A hybrid approach combines classical and post-quantum cryptographic algorithms, allowing organizations to transition smoothly to quantum-safe cryptography while maintaining compatibility with current systems.
• Performance and Resource Considerations: Post-quantum cryptographic algorithms often require more computational resources than their classical counterparts. Organizations must assess their infrastructure’s capability to handle these increased demands.
• Integration with Existing Infrastructure: Seamless integration with existing systems is crucial. Organizations should evaluate their current cryptographic implementations and identify areas where post-quantum algorithms can be incorporated. For organizations running on legacy infrastructure, post-quantum migration may require legacy application modernization before new cryptographic protocols can be integrated cleanly. Coderio’s Legacy Application Migration services address this dependency directly.
• Practical Steps for Quantum Readiness: To achieve quantum readiness, organizations should start by assessing their current cryptographic posture, identifying areas vulnerable to quantum attacks, and developing a roadmap for adopting post-quantum cryptography.

A 2024 survey by the Ponemon Institute found that only 28% of organizations had begun formal planning for post-quantum cryptography. Among those that had, the most commonly cited barrier was the complexity of the cryptographic inventory process — identifying where encryption is used across the organization before any migration can begin.

A Practical Migration Roadmap for Organizations

Understanding the concept of post-quantum cryptography is one thing. Knowing how to move your organization toward quantum-safe infrastructure is another. The following roadmap reflects the approach that security teams and technology leaders are using in practice.

Step 1: Cryptographic inventory

Before anything else, map every place cryptography is used across your organization. This includes TLS certificates, code signing, VPNs, APIs, data-at-rest encryption, authentication systems, and any third-party services that handle encrypted data on your behalf. Most organizations discover more cryptographic dependencies than they expected. The inventory is the foundation on which everything else builds.

Step 2: Risk and exposure assessment

Once you have the inventory, prioritize by exposure. Ask two questions for each system: how sensitive is the data it protects, and how long does that data need to remain confidential? Systems protecting data with a 10-year or longer confidentiality requirement are the most urgent because they are already vulnerable to harvest-now, decrypt-later attacks, even before a cryptographically relevant quantum computer exists.

Step 3: Adopt a hybrid transition approach

A full cutover to post-quantum algorithms in a single step is not realistic for most organizations. A hybrid approach runs classical and post-quantum algorithms in parallel during the transition period. This maintains compatibility with systems that have not yet migrated while adding quantum-resistant protection to those that have. Most major TLS libraries and VPN vendors already support hybrid key exchange configurations.

Step 4: Prioritize NIST-standardized algorithms

For new implementations and systems being updated, build around ML-KEM for key encapsulation and ML-DSA for digital signatures. These are the finalized NIST standards and will be the algorithms that vendors, regulators, and auditors expect to see. Avoid proprietary or non-standardized quantum-resistant solutions unless there is a specific technical reason.

Step 5: Update certificates, keys, and protocols

Work through your inventory systematically, replacing RSA and elliptic-curve certificates with post-quantum alternatives as your certificate authority and toolchain support allow. Update protocol configurations to enable post-quantum cipher suites. Document every change for audit and compliance purposes.

Step 6: Test for performance and compatibility

Post-quantum algorithms have larger key sizes and, in some cases, higher computational overhead than their classical counterparts. Test thoroughly in staging environments before deploying to production, particularly for latency-sensitive applications, IoT devices with constrained resources, and high-volume transaction systems.

Step 7: Establish ongoing monitoring and governance

Migration is not a one-time project. As quantum computing advances and cryptanalysis of post-quantum algorithms continues, standards may evolve. Build in a process for monitoring NIST updates, CISA advisories, and vendor security bulletins. Assign clear ownership for cryptographic governance within your security team. Organizations that need external support for this process can work with Coderio’s Digital Security Studio to design and implement a governance framework that fits their compliance requirements.

Real-World Applications and Use Cases

As quantum computing advances, various sectors are turning to post-quantum cryptography for future-proof security. This shift is crucial for protecting sensitive information across different industries.

• Financial Services Security: Financial institutions are among the first to adopt post-quantum cryptographic solutions to secure transactions and protect customer data. Post-quantum encryption algorithms can safeguard financial data against the potential threats posed by quantum computers. Financial institutions undergoing post-quantum migration are often doing so alongside broader core system modernization work. Coderio’s Banking Modernization Studio supports financial institutions managing both priorities simultaneously.
• Government and Military Applications: Government and military organizations are also prioritizing the implementation of post-quantum cryptography to secure classified information and maintain national security. The use of quantum-resistant algorithms is critical in these sectors.
• Healthcare Data Protection: In healthcare, post-quantum cryptography can protect patient data and medical records. This is particularly important as the healthcare industry becomes increasingly digitized.
• Secure Communications and IoT: Post-quantum cryptography can enhance the security of IoT devices and communication networks, protecting against potential quantum attacks. This is vital for maintaining the integrity of data transmitted across these networks.

The financial sector is moving faster than most. The Bank for International Settlements published guidance in 2024 recommending that financial institutions begin planning for post-quantum migration immediately. Several major banks, including JPMorgan Chase and HSBC, have announced active post-quantum cryptography programs. In the U.S., the National Institute of Standards and Technology estimates that migrating federal government systems alone will take 10 to 15 years, which is why the work started before the standards were finalized.

Challenges and Limitations in Adopting Quantum-Safe Solutions

As organizations prepare for the post-quantum era, they face numerous challenges in adopting quantum-safe solutions. The transition to quantum-resistant cryptography requires significant updates to existing infrastructure and practices.

• Technical Implementation Challenges: One of the primary challenges is the technical complexity of implementing post-quantum cryptographic algorithms. These new algorithms often require more computational resources and have larger key sizes, which can impact performance. The technical complexity of post-quantum migration is one reason many organizations treat it as a digital transformation initiative rather than a security patch. Coderio’s Digital Transformation Services support organizations working through that broader infrastructure change.
• Organizational Readiness Assessment: Organizations must assess their readiness for quantum-safe solutions by evaluating their current cryptographic practices and identifying areas for improvement. 
• Cost and Resource Implications: The adoption of quantum-safe solutions also has cost and resource implications. Organizations need to invest in new hardware and software, as well as training personnel.
• Regulatory and Compliance Considerations: Furthermore, regulatory and compliance considerations play a crucial role. Organizations must ensure that their quantum-safe solutions comply with relevant regulations and standards.

Frequently Asked Questions

1. When will quantum computers be able to break today’s encryption?

Most credible estimates from government agencies and academic researchers place the emergence of a cryptographically relevant quantum computer — one powerful enough to break RSA-2048 or elliptic curve cryptography — between 2030 and 2035. Some researchers argue the timeline could be shorter. The U.S. government’s operational planning treats 2035 as the target deadline for completing post-quantum migration of national security systems. For organizations whose data needs to remain confidential beyond that window, the migration planning needs to start now.

2. What is the difference between quantum cryptography and post-quantum cryptography?

These are two distinct fields that are frequently confused. Quantum cryptography uses the physical properties of quantum mechanics — particularly quantum key distribution (QKD) — to secure communications. It requires specialized hardware and quantum communication channels. Post-quantum cryptography, by contrast, develops classical mathematical algorithms that run on conventional computers and are designed to resist attacks from quantum computers. Post-quantum cryptography is the practical path for most organizations because it works on existing hardware and infrastructure.

3. Is AES encryption quantum-safe?

Symmetric encryption algorithms like AES are less vulnerable to quantum attacks than public-key systems like RSA or elliptic curve cryptography. Grover’s algorithm, the main quantum threat to symmetric encryption, effectively halves the security level of a symmetric key — meaning AES-128 would offer only 64-bit security against a quantum attacker, while AES-256 would retain approximately 128-bit security. For most use cases, AES-256 is considered quantum-safe. The primary concern in migration is public-key cryptography, which is completely broken by Shor’s algorithm.

4. How long does post-quantum migration take?

The timeline varies significantly depending on the size and complexity of the organization. NIST estimates that migrating U.S. federal government systems will take 10 to 15 years in total. For a mid-sized enterprise with a well-documented technology stack, initial hybrid transition work can begin within 6 to 12 months of completing a cryptographic inventory. The longest phase is typically the systematic replacement of certificates, keys, and protocols across legacy systems — particularly where vendor support for post-quantum algorithms is still maturing.

5. What is a cryptographic inventory, and why does it matter?

A cryptographic inventory is a complete map of every place encryption is used within an organization: TLS certificates, code signing, VPNs, APIs, databases, authentication systems, and third-party services. It is the essential first step of any post-quantum migration because you cannot migrate what you have not identified. Most organizations find that the inventory process takes longer than expected and reveals significantly more cryptographic dependencies than their teams were aware of.

Conclusion: Preparing for the Post-Quantum Era

As the world moves closer to the advent of quantum computing, the need for post-quantum cryptography has become increasingly evident. The potential for quantum computers to break traditional encryption methods poses a significant threat to data security. Organizations must prepare for the post-quantum era by transitioning to quantum-safe encryption solutions.

Post-quantum cryptography offers a range of algorithms and techniques designed to be resistant to quantum attacks. By adopting these solutions, organizations can ensure the long-term security of their data. The future of cryptography hinges on the successful implementation of post-quantum cryptographic protocols, which enable secure communication and protect sensitive information.

As the cryptographic landscape continues to evolve, organizations need to stay informed and adapt to the changing security requirements. By doing so, they can safeguard their data and maintain the trust of their customers and stakeholders.

For organizations that want support building a quantum-safe security posture — from cryptographic inventory through hybrid transition and ongoing governance — Coderio’s Digital Security Studio is available to help. Schedule a conversation with our security experts.