Post-quantum encryption 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, organisations have relied on encryption algorithms that are considered secure against attacks from classical computers. However, advances in quantum computing are changing that assumption. As a result, post-quantum encryption is becoming an essential topic for security leaders responsible for protecting data not just today, but for years or decades to come.
Post-quantum encryption is not about reacting to an immediate crisis or chasing speculative technology. It is about recognising 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 post-quantum encryption is, why it matters now rather than later, and how organisations can realistically begin the transition without disruption. It is written for security decision-makers who need clarity, confidence and practical guidance, not alarm or unnecessary complexity.
Why post-quantum encryption is critical today
Quantum computing has the potential to fundamentally change how certain types of 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 widespread 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 once they reach sufficient scale and stability.
The challenge for cybersecurity leaders is timing. Encryption 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 organisations 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 encryption matters because it allows organisations to prepare in advance, reducing future risk without requiring sudden or disruptive change.
What is post-quantum encryption?
Post-quantum encryption refers to cryptographic algorithms and systems designed to remain secure even against attackers with access to powerful quantum computers.
In plain terms, it means 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 encryption from several commonly confused concepts:
- Post-quantum encryption is not quantum encryption: 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.
- It is not a claim of being permanently unbreakable: Like all cryptography, post-quantum encryption is based on current knowledge and assumptions, with an emphasis on resilience and adaptability.
At its core, post-quantum encryption is about designing 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 encryption differs from classical encryption
Classical public key encryption relies on problems such as integer factorisation 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 have been trusted for decades.
Post-quantum encryption 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 post-quantum encryption 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 rather than a single event.
Common misconceptions about post-quantum encryption
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 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 organisations to focus effort where it is genuinely needed rather than assuming a universal failure of cryptography.
Another widespread belief is that post-quantum encryption must be adopted immediately across all systems. This can create unnecessary pressure and the impression that organisations are already behind. In practice, post-quantum readiness is about long-term planning, visibility and flexibility. Most organisations will transition incrementally, prioritising systems with long lifespans or sensitive data rather than attempting wholesale replacement.
There is also frequent confusion between post-quantum encryption and quantum key distribution. Quantum key distribution relies on specialised quantum hardware and physical constraints that limit scalability and practicality for many environments. Post-quantum encryption, by contrast, is designed to run on existing infrastructure and integrate with current security architectures.
Clarifying these misconceptions helps security leaders 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 quantum algorithm 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. These capabilities would directly undermine the security assumptions behind widely used algorithms such as RSA and elliptic curve cryptography.
This does not mean quantum computers will make all cryptography obsolete. Symmetric encryption and hash functions are far more resilient to quantum attacks, especially when appropriate key sizes are used. The impact is concentrated on public key mechanisms used for key exchange and digital signatures.
From a cybersecurity perspective, this distinction is important. It allows organisations to focus their efforts where the risk is real, rather than attempting to replace every cryptographic control at once.
Which cryptographic systems are affected
Public key encryption and digital signature schemes based on factorisation 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 prioritise migration efforts and avoid unnecessary disruption.
The real-world risk timeline
One of the most challenging aspects of post-quantum encryption is that the risk does not align neatly with visible technological milestones.
Large-scale, cryptographically relevant quantum computers do not yet exist. However, the risk is already present due to the longevity of data and systems.
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 waiting a risky strategy for organisations handling long-lived data.
Long-lived systems and devices
In sectors such as telecommunications, automotive, industrial IoT and defence, systems may remain in service for decades. Cryptographic choices made at design time can be extremely difficult to change later.
These realities mean that post-quantum encryption is a present-day planning issue, even if the most dramatic impacts lie in the future.
Post-quantum encryption standards
Ensuring trust, interoperability and long-term security requires that post-quantum encryption is based on open, internationally recognised standards. Without these standards, organisations 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 formalisation 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 organisations, 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 organisations reassurance that their encryption strategies are grounded in science, not speculation.
Aligning a post-quantum strategy with emerging standards allows organisations to progress confidently without committing prematurely to technologies that may not endure. It also helps plan migration paths that are flexible and sustainable, enabling a smooth transition to quantum-safe security without disrupting existing infrastructure.
By following standards, organisations 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 post-quantum encryption 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 post-quantum encryption does not require immediate replacement of all cryptographic systems. Instead, organisations 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. This allows organisations to maintain compatibility while gaining quantum resistance.
4. Integrate into risk management
Post-quantum encryption 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 post-quantum encryption 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 organisations 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 organisations, the hardest part of post-quantum encryption 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 that 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 organisations to prioritise action based on real exposure rather than theoretical threat. 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 organisations operating in regulated environments or deploying systems with long service lives.
By combining standards expertise with deployable software and hardware solutions, PQShield helps organisations 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 encryption 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.
For most organisations, the right response is calm, informed and incremental. Understand where cryptography matters most. Align with emerging standards. 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.
Post-quantum encryption is ultimately about trust. Trust that data will remain confidential. Trust that systems will continue to function securely. And trust that cybersecurity strategies are built not just for the present, but for the future.
Speak to our trusted team today to better understand your post-quantum options.