Post-quantum cryptography for modern security
Encryption underpins almost every aspect of modern digital security. From protecting sensitive data and securing communications to verifying identities and safeguarding software updates, cryptography is the foundation on which trust in digital systems is built.
For decades, organizations have relied on cryptographic algorithms that are considered secure. However, advances in quantum computing are changing that assumption. As a result, Post-Quantum Cryptography (PQC) is becoming an essential topic for security leaders responsible for protecting data – not just today, but for years, or even decades to come.
Adapting to the quantum threat is not about reacting to an immediate crisis or chasing speculative technology. It is about recognizing that cryptographic decisions made today have long-term consequences. Data, devices and infrastructure often outlive the algorithms designed to protect them. Preparing for a post-quantum world is therefore a matter of prudent cybersecurity planning, risk management and future-proofing.
This page explains what PQC is, why it matters, and how organizations can realistically begin the transition without disruption. It’s designed to provide confidence and practical guidance, rather than alarm or unnecessary complexity.
Why post-quantum cryptography is critical today
Quantum computing has the potential to fundamentally change how certain problems can be solved. While today’s quantum computers are still limited, progress is steady, and the long-term implications for cryptography are well understood.
Many of the public key encryption algorithms in use today rely on mathematical problems that are extremely difficult for classical computers to solve. Quantum computers, however, could solve these problems far more efficiently when they reach sufficient scale and stability.
The challenge for cybersecurity leaders is timing. Cryptography protects information across its entire lifecycle, not just at the moment it is created or transmitted. Data encrypted today may need to remain confidential for decades. Devices deployed now may remain operational long after quantum capabilities mature.
This creates a strategic problem. If organizations wait until quantum computers are demonstrably capable of breaking current encryption, it may already be too late to protect long-lived data and systems. Post-quantum cryptography matters because its implementation allows organizations to prepare in advance, reducing future risk without requiring disruptive change.
What is post-quantum encryption?
Post-quantum cryptography refers to algorithms and systems designed to remain secure against attackers with access to powerful quantum computers.
In plain terms, it a post-quantum upgrade would require replacing or augmenting today’s vulnerable public key cryptography with new algorithms based on different mathematical foundations that are believed to be resistant to both classical and quantum attacks.
It is important to distinguish post-quantum cryptography from several commonly confused concepts:
- PQC is not quantum: It does not require quantum hardware to deploy or use. It runs on classical computers and networks.
- It is not speculative or experimental: Post-quantum algorithms are being rigorously analysed, tested and standardised by international bodies.
- PQC does not claim to be permanently unbreakable: Like all cryptography, PQC is based on current knowledge and assumptions, with an emphasis on resilience and adaptability.
At its core, PQC is about designing agile cryptographic systems that can survive technological change. Rather than assuming today’s algorithms will remain secure indefinitely, it acknowledges that cryptography must evolve alongside computing capabilities.
How post-quantum cryptography differs from classical
Classical public key cryptography relies on the complexity of mathematical problems such as integer factorization and discrete logarithms. These problems are computationally infeasible for classical computers to solve at scale, which is why algorithms like RSA and elliptic curve cryptography (ECC) have been trusted for decades.
Post-quantum cryptography uses alternative mathematical structures, such as lattices, hash functions or error-correcting codes. These problems do not currently have known efficient solutions using either classical or quantum computers.
From an operational perspective, the shift to PQC is not always straightforward. Post-quantum algorithms often have different performance characteristics, key sizes and implementation considerations. This is why the transition is best approached as a gradual evolution.
Common misconceptions about PQC
As interest in quantum security grows, so does confusion. The term post-quantum is often used inconsistently, leading to misconceptions that can distort risk perception and complicate decision-making. Addressing these misunderstandings is an important step towards a measured, effective approach.
One common misconception is that quantum computing will instantly break all encryption. In reality, the impact of quantum computing is likely to be specific and targeted. Only certain types of public key cryptography are vulnerable, and even then only once sufficiently powerful and stable quantum computers exist. Symmetric encryption and hash-based mechanisms remain largely secure when used with appropriate parameters. This distinction matters, as it allows organizations to focus effort on an appropriate solution rather than assuming a universal failure of cryptography.
Another widespread belief is that PQC must be adopted immediately across all systems. This can create unnecessary pressure and the impression that organizations are already behind. In practice, post-quantum readiness is about long-term planning, visibility and flexibility. Most organizations will transition incrementally, prioritizing systems with long lifespans or sensitive data rather than attempting wholesale replacement.
There is also confusion between post-quantum cryptography and Quantum Key Distribution (QKD). Quantum key distribution relies on specialized quantum hardware and physical constraints that limit scalability and practicality for many environments. Post-quantum cryptography, by contrast, is designed to run on existing infrastructure, and integrates with current security architectures.
Clarifying these misconceptions helps avoid both complacency and overreaction, enabling informed, proportionate decisions that align with real-world risk and operational reality.
Why quantum computing breaks today’s encryption
The primary reason quantum computing threatens current public key encryption lies in a mathematical tool known as Shor’s algorithm.
Shor’s algorithm demonstrates that a sufficiently powerful quantum computer could efficiently factor large numbers, and solve discrete logarithm problems. The ability to do this would directly undermine the security assumptions behind widely used algorithms such as RSA and ECC.
This does not mean quantum computers will make all cryptography obsolete. Symmetric encryption and hash functions are inherently more resilient to quantum attacks, especially when appropriate key sizes are used. The quantum impact is concentrated on public key mechanisms used for key exchange and digital signatures.
From a cybersecurity perspective, this distinction is important. It allows organizations to focus their efforts where the risk is real, rather than attempting to replace every cryptographic control at once.
Which cryptographic systems are affected?
Encryption schemes that rely on integer factorization or discrete logarithms are the most vulnerable to quantum attacks. These are used extensively in secure communications, identity management, and software integrity.
Symmetric encryption algorithms such as AES are less affected. Quantum attacks can reduce their effective security strength, but this can be mitigated by using longer keys.
Hash functions are also relatively robust, although key lengths and usage patterns may need adjustment over time.
Understanding this landscape allows security teams to prioritize migration efforts.
The real-world risk timeline
One of the most challenging aspects of implementing PQC is that the risk does not align neatly with visible technological milestones.
Large-scale, cryptographically relevant quantum computers do not yet exist. However, with long-lasting data and systems likely to be in place for years to come, the risk is already present.
Long data lifetimes
Many types of sensitive data must remain confidential for long periods. This includes personal data, medical records, financial information, trade secrets, and classified material. If such data is intercepted and stored today, it may be decrypted years later.
‘Harvest now, decrypt later’
Adversaries do not need quantum computers today to exploit quantum risk. They can collect encrypted data now and decrypt it once quantum capabilities mature. This makes delaying a quantum upgrade a risky strategy for organizations handling long-lived data.
Long-lived systems and devices
In sectors such as telecommunications, automotive, industrial IoT, and defence, systems can remain in service for decades. Cryptographic choices made at design time can be extremely difficult to change later.
This means that quantum resilience is a present-day planning issue, even if the most dramatic impacts are yet to come.
Post-quantum cryptography standards
Ensuring trust, interoperability, and long-term security requires that quantum resistance is based on internationally recognized standards. Without these standards, organizations risk implementing solutions that may be incompatible, insecure, or short-lived.
Leading standards bodies, such as the National Institute of Standards and Technology (NIST), are spearheading the evaluation, selection, and formalization of post-quantum cryptographic algorithms. This is not a quick process: each candidate algorithm undergoes extensive public scrutiny, cryptanalysis, and practical testing. By inviting global cryptography experts to examine these algorithms, standards bodies aim to identify robust, future-proof solutions that can withstand both classical and quantum computing threats.
For organizations, adhering to standards-based post-quantum cryptography offers several practical advantages:
- Avoid reliance on proprietary or unproven algorithms: Using well-studied and vetted algorithms minimises the risk of introducing hidden vulnerabilities or investing in technologies that may be retired.
- Support interoperability across platforms and vendors: Standardised algorithms ensure that different systems, devices, and software can securely communicate, reducing complexity and integration costs.
- Provide confidence in algorithm security: Standards-based solutions have undergone rigorous evaluation, giving organizations reassurance that their cryptography strategies are grounded in science, rather than speculation.
Aligning a post-quantum strategy with emerging standards allows organizations to progress confidently without committing prematurely to technologies that might not endure. Alignment also enables organizations to plan flexible and sustainable migration paths, ensuring a smooth transition to quantum-safe security without disrupting existing infrastructure.
By following standards, organizations can not only safeguard sensitive data today but also prepare for a future where quantum computing is a reality – protecting information, maintaining trust, and ensuring operational resilience.
Migration challenges and practical constraints
While the case for PQC is clear, the path to adoption is not without challenges.
Performance and resource constraints
Some post-quantum algorithms require larger keys or more computation than classical alternatives. This can affect performance, latency and memory usage, particularly in constrained environments.
Hardware and embedded systems
Devices with limited processing power or fixed hardware may struggle to support new algorithms without careful optimisation or hardware acceleration.
Legacy systems
Many organisations operate complex environments with legacy systems that cannot easily be updated. These systems still need to be accounted for in post-quantum planning.
Operational complexity
Cryptography is often deeply embedded in applications and workflows. Changing it without disrupting operations requires careful design and testing.
These challenges reinforce the need for incremental, well-planned migration rather than abrupt change.
How organisations can start the transition
Preparing for quantum resilience does not require immediate replacement of all cryptographic systems. Instead, organizations can take practical steps that build readiness over time.
1. Establish cryptographic visibility
Understanding where and how cryptography is used across systems, applications, and supply chains is a critical first step. This includes identifying algorithms, key lengths and dependencies.
2. Build crypto-agility
Crypto-agility is the ability to change cryptographic algorithms without redesigning entire systems. This involves modular architectures, abstraction layers, and clear separation between cryptography and application logic.
3. Use hybrid approaches
Hybrid cryptographic schemes combine classical and post-quantum algorithms during transition periods, providing protection against both traditional and quantum attack. This allows organizations to maintain compatibility while gaining quantum resistance.
4. Integrate into risk management
PQC implementation should be considered as part of broader cybersecurity risk management, rather than as a standalone technical project.
By taking these steps, organisations can move forward with confidence and flexibility.
Where does PQShield come in?
Navigating the transition to quantum-resilience requires both deep cryptographic expertise and a practical understanding of real-world systems. PQShield exists at the intersection of these needs.
Founded as a spin-out from the University of Oxford, PQShield brings together world-class cryptographers, engineers and security specialists. The team plays an active role in shaping international post-quantum cryptography standards, helping ensure that emerging algorithms are robust, practical and suitable for deployment.
PQShield focuses on enabling post-quantum encryption across software, hardware and cloud environments. Its solutions are designed to integrate into existing systems, supporting hybrid approaches and crypto-agility rather than forcing disruptive change.
By working with organizations in regulated and long-lifecycle industries, PQShield helps security leaders assess quantum risk, plan migration strategies and deploy quantum-safe cryptography in a way that aligns with operational realities.
The emphasis is not on selling fear or speculative technology, but on providing clarity, confidence and deployable security that stands the test of time.
Working with PQShield on post-quantum encryption
For many organizations, the hardest part of implementation is not understanding the risk but knowing how to move forward in a way that is practical, proportionate, and aligned with long-term security goals. Working with PQShield helps bridge the gap between strategy and implementation.
PQShield works alongside security teams to assess where quantum risk is most relevant across data, systems and product lifecycles. This enables organizations to prioritize action based on real exposure rather than theoretical threats. The approach is collaborative and structured, helping teams develop clear roadmaps that balance security, performance, and operational constraints.
A key focus is enabling crypto-agility. PQShield supports architectures that allow cryptographic components to be updated as standards mature, without requiring disruptive system redesigns. This is particularly important for organizations operating in regulated environments or deploying systems with long-service lives.
By combining standards expertise with deployable software and hardware solutions, PQShield helps organizations adopt hybrid and post-quantum cryptography in a controlled, future-ready way. The result is not rushed migration, but informed preparation that builds confidence in both current security posture and long-term resilience.
Preparing for the next era of cybersecurity
Post-quantum resilience represents a natural evolution of cybersecurity in response to changing technology. It is not a signal that today’s security has failed, but a recognition that long-term protection requires foresight and adaptability.
The best response is calm, informed and incremental, understanding where cryptography matters most in an organization’s infrastructure. It’s important to align with emerging standards and build systems that can evolve without disruption.
By acting early and thoughtfully, security leaders can reduce future risk while maintaining stability today. Preparation, not panic, is the defining principle of post-quantum security.
Quantum resilience is ultimately about trust: that data will remain confidential, that systems will continue to function securely, and that the cybersecurity strategies we build are not just for the present, but for the future.
Speak to our trusted team today to better understand your post-quantum options.